ESO SL-9/Jupiter Information Package
THE COLLISION BETWEEN COMET SHOEMAKER-LEVY 9 AND JUPITER
(JULY 16 - 22, 1994)
THE ESO SL-9/JUPITER INFORMATION PACKAGE
Background information for the media
Produced by the ESO Information Service
Date of Issue: July 5, 1994
Click here to jump to 2. A Brief Summary of the Event
Click here to jump to 3. The Possible Effects
Click here to jump to 4. Basic Information and Tables
Click here to jump to 5. ESO & Observations at La Silla
Click here to jump to 6. ESO's Services to the Media
1. Introduction
1.1 General
This Information Package contains background information which will be
useful in connection with the media coverage of the collision between
Comet Shoemaker-Levy 9 and the planet Jupiter on July 16 - 22, 1994.
It provides a general overview of the main issues around this unique
astronomical event, the like of which has never before been predicted,
nor observed.
The complete package consists of:
- A comprehensive text, describing the event, the planned observations
(especially at ESO) and the possible implications;
- A series of photos, illustrating the preparations; and
- A video tape with (unedited) illustrative sequences, suitable for
broadcast use. Available in various formats.
Copies of the ESO SL-9/Jupiter Information Package or parts thereof
may be requested from:
ESO Information Service
European Southern Observatory
Karl-Schwarzschild-Strasse 2
D-85748 Garching bei Muenchen
Germany
Tel.: +49-89-32006-276
Fax.: +49-89-3202362
1.2 Acronyms
A number of common acronyms are used in this brochure:
B&C Boller & Chivens spectrograph (at ESO 1.5-metre telescope)
CAT 1.4-metre Coude Auxiliary Telescope
CES Coude Echelle Spectrograph (at CAT and 3.6-metre telescope)
CEST Central European Summer Time (= UT + 2 hours)
EMMI ESO Multi-Mode Instrument (at the New Technology Telescope)
ESA European Space Agency
ESO European Southern Observatory
Far-IR Far-infrared wavelength region (about 5 - 20 microns)
IRAC2B Infrared Astronomical Camera 2B (at MPG/ESO 2.2-metre telescope)
IRSPEC Infrared Spectrograph (at the New Technology Telescope)
JPL Jet Propulsion Laboratory (Pasadena, California, USA)
MPIA Max-Planck-Institut fuer Astronomie (Heidelberg, Germany)
MPIAe Max-Planck-Institut fuer Aeronomie (Katlenburg-Lindau, Germany)
MPG Max-Planck-Gesellschaft (Germany)
Near-IR Near-infrared wavelength region (about 0.8 - 5 microns)
NTT ESO 3.5-metre New Technology Telescope
SEST 15-metre Swedish-ESO Submillimetre Telescope
ST/ECF Space Telescope/European Coordinating Facility (at ESO-Garching)
TIMMI Thermal Infrared Multi-Mode Instrument (at the 3.6-metre telescope)
UBVRI Standard five-colour photometric system in astronomy (from
about 380 nm to 900 nm wavelength)
UT Universal Time (earlier Greenwich Mean Time)
VLT ESO 16-metre equivalent Very Large Telescope (under construction
at Cerro Paranal, Chile)
2. A Brief Summary of the Event
Beginning in the evening of July 16, 1994 (CEST = Central European
Summer Time), fragments of Comet Shoemaker-Levy 9 will collide with
Jupiter, the largest planet in the Solar System. The comet was
discovered in March 1993, and its nucleus which may be likened with a
"dirty snowball" of ice and dust, broke into more than 20 pieces
during a close passage near Jupiter in July 1992. All of these
fragments, which measure from a few hundred metres to a few kilometres
in diameter, will hit Jupiter during a period of about 5 1/2 days,
lasting until the morning of July 22. Astronomers all over the world
now prepare to observe the associated phenomena with ground- and
space-based astronomical instruments.
Images of the comet have been obtained during the past few days with
telescopes at the ESO La Silla observatory (Chile) and elsewhere.
They confirm that there have only been minor changes and that at least
20 cometary fragments are still present. These observations have also
led to more precise predictions of the times of the impacts.
The collisions will all take place on the far side of Jupiter and can
therefore not be directly observed from the Earth. However, due to the
rapid rotation of the planet, the impact sites will come into view
within 10 - 15 minutes and it is likely that certain effects in the
Jupiter atmosphere will then become noticeable.
Each collision will result in the complete destruction of the comet
fragment in the dense atmosphere of Jupiter. Depending of the mass of
the individual fragments, the energy released may approach the
equivalent of several 100,000 Megatons. Various effects have been
predicted, ranging from an initial light flash when the comet
fragments disintegrate, a subsequent rising column of superheated
gases which may form a visible "mushroom" structure, as well as new
eddies and whirls in the atmosphere, vibrations of the entire planet,
and disturbances in the strong magnetic field, in turn leading to
variations in Jupiter's intense radio emission.
Observations have been planned at many professional observatories all
over the world; due to Jupiter's position in the southern sky, the
best observing conditions will be in the southern hemisphere (South
America, Australia, South Africa). An international collaboration has
been set up, linking the observers by computer networks which will
ensure that information about all new developments can be rapidly
passed on.
At the ESO La Silla observatory in Chile, ten telescopes with a total
of twelve observing programmes will be active during the critical
period.
Due to the lack of knowledge of the exact sizes and internal structure
of the individual comet fragments, it has proven extremely difficult
to make predictions about the magnitudes of the expected effects. For
this reason, it is in principle not possible to state in advance what
will actually be observed. It is believed, however, that the
observations will provide new knowledge about the following important
subjects:
- Internal structure and composition of cometary nuclei ("dirty snowballs");
- Composition and structure of the deeper layers of Jupiter's atmosphere;
- Jupiter's inner structure; and
- The overall effects of such collisions.
The last point is of direct interest to mankind, since comets have
collided with the Earth in the past and are bound to do so in the
future, albeit only very rarely.
3. The Possible Effects
Below is a condensed overview of the event and the possible effects,
how it is intended to observe them, as well as information about the
main uncertainties.
3.1 What will happen ?
There is absolutely no doubt that the collisions will indeed take
place. It is equally certain that they will happen on the rear side
of Jupiter, just behind the visible limb and at about 45 degrees
southern latitude.
Accurate positional measurements of the comet fragments during the
past year have made it possible to determine their orbits with very
high precision, and we know at present the location of most fragments
to within a few hundred kilometres. Jupiter's diameter is so large,
just over 140,000 kilometres (that is, 11.2 times larger than that of
the Earth), that any conceivable last-minute corrections to the orbits
will only result in minor changes of the impact locations and times.
The first fragment will hit Jupiter on July 16, 1994, at around 19:30
UT (21:30 CEST; 15:30 Chilean time) and the last 5 1/2 days later, on
July 22, 1994, around 08:00 UT (10:00 CEST; 04:00 Chilean time). These
timings are still subject to improvement, but the events will probably
not occur more than 30 minutes earlier or later.
The comet fragments will hit Jupiter at a very high velocity, about 60
km/sec. The correspondingly large motion energy (the "kinetic energy")
will all be deposited in the Jovian atmosphere. For a 1 km fragment,
it is equal to about 10^28 erg, or 250,000 Megatons (approximately 12
million times the energy released by the Hiroshima bomb).
When one of the cometary fragments enters the upper layers of the
Jovian atmosphere, it will be heated by the friction with the
surrounding molecules, exactly as a meteoroid in the Earth's
atmosphere. The speed will decrease very rapidly and depending on the
size of the fragment, it may evaporate completely within a few
seconds, while it is still above the dense cloud layers that form the
visible "surface" of Jupiter, or it may plunge right through these
clouds (and therefore out of sight) into increasingly denser, lower
layers. Whatever the altitude, it ultimately comes to a complete stop
and disintegrates in a giant explosion.
All of the kinetic energy is released during this process. One part
will heat the surrounding atmosphere to very high temperatures; this
will result in a flash of light that lasts a few seconds. Within the
next minutes, a plume of hot gas (a "mushroom cloud") will begin to
rise over the impact site. It may reach an altitude of several hundred
kilometres above the cloud layers and will soon spread out in all
horizontal directions. It will quickly mix with the upper layers of
the atmosphere and it is possible that new whirls and eddies are
produced.
Another part of the released energy will be transformed into shock
waves that will propagate around the planet in the lower layers of the
atmosphere and also into the interior of Jupiter, much as seismic
waves from an earthquake do inside the Earth. When these waves again
reach the upper layers of the atmosphere, they may be seen as slight
increases of the local temperature along expanding circles with the
impact sites at their centres (like waves on a water surface). The
shock waves may also start oscillations of the entire planet, like
those of a ringing bell.
It is also expected that there will be some kind of interaction
between the cometary dust and Jupiter's strong magnetic field. For
instance, the fast-moving dust grains may become electrically
charged. This will possibly have a significant influence on Jupiter's
radio emission and therefore be directly observable with Earth-based
radio telescopes, as well as from several spacecraft.
Some of the dust may be deposited in the upper layers of the
atmosphere and could possibly induce some colour changes of some of
the cloud patterns.
There may also be changes in the plasma torus that girdles Jupiter
near the orbit of the volcanic moon Io, and some cometary dust
particles may collect in Jupiter's faint ring.
3.2 Which are the main uncertainties ?
Both Jupiter and the cometary fragments have been extensively observed
during the past months. However, while we now possess more accurate
information about the comet's motion and the times of impact, there is
still great uncertainty about the magnitude of the above mentioned
effects.
It is at this moment not clear which of them may actually be observed
at the time of the impacts and which will be too weak to be
observable, even with the largest and best telescopes.
This is first of all due to the fact that it has not been possible to
measure the sizes and masses of the individual cometary fragments and
thereby to estimate the amount of energy which will be liberated at
the collisions. Only rough estimates, based on the behaviour of the
fragments and a comparison with other comets, are available. It is
generally agreed that the smallest fragments measure at most a few
hundred metres across, but there are divided opinions about the size
of the largest. Conservative estimates put them at around 1, perhaps 2
kilometres in diameter, more optimistic guesses quote figures of 4 - 5
kilometres. Moreover, the internal constitution of the fragments is
completely unknown. It clearly makes a difference, whether they are
rather compact objects, or if they consist of very loose material; the
first will penetrate much deeper into the atmosphere before they
disintegrate than the second.
Despite intensive observations, no gas has yet been detected in any of
the fragments. We only see clouds of dust around them which completely
hide them from our view. The amount of the dust has been steadily
decreasing; this is because the dust production from the individual
fragments - which began when the parent body broke up at the time of
the near-collision with Jupiter in July 1992 - is slowly diminishing
with time.
Some of the smaller nuclei have recently disappeared from view,
probably because they have ceased to produce dust. It is not clear,
however, whether this also implies that they no longer exist at all,
or whether they are just too small to be seen with available
telescopes.
3.3 Why is this event of interest ?
This event offers a unique opportunity to obtain new and exciting
information about the colliding objects and the collision process
itself. It is in fact a "cosmic experiment" of a type that has never
before been observed by astronomers. Since very little is known about
the actual effects that will be observed, the scientists have prepared
themselves for different scenarios. There may be complete surprises,
or the predicted effects may be too weak to perform accurate
measurements. Whatever happens, new knowledge about this dramatic
phenomenon will be collected.
Here are the main subjects which will be studied.
The structure of cometary nuclei:
The internal structure and composition of cometary nuclei, often
likened to "dirty snowballs", is still completely unknown. The images
of the nucleus of comet Halley and other measurements of this famous
comet, obtained from spacecraft and by ground-based telescopes in
1986, never allowed a view below the surface of the very dark, 15-km
nucleus.
The disintegration process of the fragments of comet Shoemaker-Levy 9
in Jupiter's atmosphere will depend on their inner structure and
observations of the associated phenomena may therefore allow some
conclusions about this structure. Any new information on this subject
will be extremely valuable for cometary physics and our understanding
of these old objects, which we believe to harbour material that has
remained unchanged since the very beginnings of the solar system,
about 4600 million years ago.
The deeper layers of Jupiter's atmosphere:
If a comet fragment penetrates far down into the Jupiter atmosphere,
the resulting, rising column of hot gases may contain elements of this
atmosphere which could never have been observed otherwise. It may even
become possible to prove the existence of complex molecules (possibly
organic) which have not been seen before. Likewise, the time profile
of the disintegration process (what happens at which altitude ?) may
give us clues to the layering and structure of these parts of the
atmosphere.
It is expected that approximately half of the released energy will be
transferred to the surrounding atmosphere (as a "shock") and result in
wave motions, very similar to seismic waves in the Earth. Some of the
waves will move along the upper atmosphere and spread like rings on
the water. Others will traverse Jupiter's inner regions, before they
again reach the surface, far from the impact sites. The observations
of these waves will provide important clues to the deeper layers of
the atmosphere as well as the inner structure of Jupiter.
The inner structure of Jupiter:
Jupiter's inner structure is in fact completely unknown to us. While
it is expected that the main components are hydrogen and helium, it
cannot be excluded that Jupiter has an inner core of heavy elements
(metals) like the Earth. It may also be that there exists a shell of
"metallic" hydrogen, surrounding a central core of very highly
compressed helium. The observation of the seismic waves may now for
the first time give us definite clues to Jupiter's inner structure.
The effects of comet collisions:
Never before has the collision of a comet with another celestial body
been directly observed. The related computer simulations are
extremely complex and with the present state of art they must be
considered rather uncertain. The real effects of such a collision are
therefore largely unknown.
We are now in the unique situation of being able to watch such an
event at distance. In addition to the effects that will be observed at
Jupiter, a very central issue is that this may allow us to better
estimate the possible effects of such a collision, when it happens at
the Earth.
There is no doubt that comet collisions with the Earth have taken
place in the past; it is possible that the Tunguska event in 1908 was
of this kind. It occured in central Siberia and resulted in a blast
with an equivalent strength of approximately 20 - 50 Megatons. It is
equally certain that such impacts will again happen. Still, the
estimated frequency is rather low - perhaps one major catastrophe per
30 million years.
3.4 How will the collisions be observed ?
All professional astronomers agree that nobody knows for sure, how
dramatic the effects of the impacts will actually be. It is obvious,
however, that unless we are prepared to observe them, we may lose a
great chance for advancing our knowledge that is unlikely to come back
in many years, if ever.
For this reason, the observers have adopted a flexible policy. By
carefully considering the optimal types of observations, a great
variety of instruments and methods will be deployed at the large
telescopes of the world's observatories. Each instrument, be it a CCD
camera, a high-speed photometer, a long-slit spectrograph or a special
receiver at a radio telescope, will work continuously during and after
the impacts and the data will be looked at at short
intervals. Moreover, all observers and their theoretically oriented
counterparts at the computers will be in close contact during these
days, continuously exchanging the latest information.
This ensures that unexpected developments will be quickly detected,
analysed and announced so that other observers can react to them in
the shortest possible time. In this way, the observations will always
be optimized.
3.5 Could this event have implications for us on Earth ?
Apart from new knowledge about what happens by a collision with a
comet, the present event has no direct implications for life here on
Earth.
There have been wild and unfounded speculations in some places about
possible, very dramatic effects, for instance that the orbit of
Jupiter would be significantly changed, or that thermonuclear
reactions may start on that planet. It has been alleged that this
might in turn influence the Earth.
The mass of Jupiter is 318 times that of the Earth and at least 10
million million times larger than that of the comet, amply ensuring
that the collisions will introduce no discernible change in Jupiter's
orbit. The temperatures which will be reached in the atmosphere, even
if they are much higher (a few thousand degrees) than those normally
prevailing, are way below what is needed to ignite a thermonuclear
reaction, that is, several million degrees. None of the above effects
are therefore possible.
The collisions take place when Jupiter is about 770 million kilometres
from the Earth. This enormous distance may be illustrated by the fact
that it takes light, travelling at 300,000 km/sec through the very
nearly empty space between us and the planet, no less than 43 minutes
to reach us. The corresponding delay is about 1 second from the Moon.
Whatever happens at Jupiter is therefore very, very far from us and
absolutely unlikely to have the slightest influence on the Earth and
the life on this planet.
4. Basic Information and Tables
4.1 Comet Shoemaker-Levy and its orbit
Comet Shoemaker-Levy 9 is the ninth short-period comet discovered by
American astronomers Eugene and Carolyn Shoemaker and David Levy. It
was first seen on a photographic plate obtained on 18 March 1993 with
the 18-inch Schmidt telescope at the Mount Palomar Observatory,
California. It was close in the sky to Jupiter and orbital
calculations soon showed that it moves in a very unusual orbit. While
other comets revolve around the Sun, this one moves in an elongated
orbit around Jupiter with a period of just over 2 years. It was
obvious that it must have been "captured" rather recently by the
gravitational field of the planet.
It was also found that Shoemaker-Levy 9 unlike most other comets
consists of several individual bodies which move like "pearls on a
string" in a majestic procession. It was later determined that this
is because the comet suffered a dramatic break-up due to the strong
attraction of Jupiter at the time of an earlier close passage, only
20,000 kilometres (that is less than 1/3 of the radius of Jupiter)
above the cloud deck of this planet on July 8, 1992.
High-resolution Hubble Space Telescope images have shown the existence
of up to 21 individual fragments (also termed "sub-nuclei"), whose
diameters probably range between a few kilometres and a few hundred
metres. There is also much cometary dust visible around these
sub-nuclei; it is probably a mixture of grains of different sizes,
from sub-millimetre sand up to metre-sized boulders.
Subsequent observations have showed changes in the relative brightness
of the individual fragments, and many of them developed individual
comet "tails". However, despite intensive spectroscopic observations,
no gas has so far been detected in any of the nuclei, but this is not
unusual for a comet at a distance of nearly 800 million kilometres
from the Sun. We only see the dust clouds around the sub-nuclei and
they are completely hidden from our view within these clouds. The
amount of the dust has been steadily decreasing; this is because the
dust production from the individual fragments -- which began when the
parent body broke up at the time of the near-collision with Jupiter in
July 1992 - is slowly diminishing with time.
The fragments have been numbered from A to W. The largest are E, G, H,
K, L and W. A is the first to impact on Jupiter, W is the last. Some
of the smaller fragments (J, M and O) have recently disappeared from
view, probably because they have ceased to produce dust.
In addition to the observations of the physical and chemical
properties of the individual nuclei, astrometric (positional)
observations have been carried out at several observatories. They have
allowed to determine the orbits of the individual fragments and serve
to make accurate predictions for the impact times. Nevertheless, it
has not been possible to extrapolate the orbit backwards in time
beyond the near-collision in July 1992 and the earlier orbit and
origin of this comet is completely unknown. It is however likely that
it has spent a very long time (probably since the birth of the solar
system) in the outer regions of the system, until its orbit was
recently perturbed, after which it had its fateful 1992 encounter with
Jupiter.
Predicted positions of three fragments
Computations by D.K. Yeomans and P.W. Chodas / JPL (June 24, 1994)
The following tables give geocentric ephemerides for the fragments A,
Q, and W. These ephemerides are based on our latest orbital
solutions, using astrometric data through 1994 June 16 and planetary
ephemeris DE-245. 1 AU = 149.6 million kilometres.
Explanation of Symbols:
R.A. J2000 Dec. = Geocentric astrometric right ascension and declination
referred to the mean equator and equinox of J2000.
Light time corrections have been applied.
Delta = Geocentric distance of object in AU.
r = Heliocentric distance of object in AU.
Theta = Sun-Earth-Object angle in degrees.
Beta = Sun-Object-Earth angle in degrees.
Moon = Object-Earth-Moon angle in degrees.
Ephemeris (with perturbations) for Comet S-L 9, fragment A
Date (UT) h R.A. J2000 Dec. Delta r Theta Beta Moon
1994 Jul 5 00 14 09 46.99 -12 21 17.9 4.944 5.402 111.6 10.1 156
1994 Jul 5 12 14 09 51.75 -12 21 01.0 4.952 5.403 111.2 10.1 150
1994 Jul 6 00 14 09 56.74 -12 20 44.5 4.959 5.403 110.7 10.1 144
1994 Jul 6 12 14 10 01.95 -12 20 28.4 4.967 5.403 110.3 10.2 138
1994 Jul 7 00 14 10 07.39 -12 20 12.7 4.974 5.404 109.8 10.2 132
1994 Jul 7 12 14 10 13.07 -12 19 57.3 4.982 5.404 109.3 10.2 126
1994 Jul 8 00 14 10 18.98 -12 19 42.2 4.989 5.405 108.9 10.3 119
1994 Jul 8 00 14 10 18.98 -12 19 42.2 4.989 5.405 108.9 10.3 119
1994 Jul 8 12 14 10 25.13 -12 19 27.3 4.997 5.405 108.4 10.3 113
1994 Jul 9 00 14 10 31.53 -12 19 12.5 5.005 5.406 108.0 10.3 107
1994 Jul 9 12 14 10 38.18 -12 18 57.8 5.012 5.406 107.5 10.3 100
1994 Jul 10 00 14 10 45.10 -12 18 43.1 5.020 5.407 107.1 10.4 94
1994 Jul 10 12 14 10 52.29 -12 18 28.3 5.028 5.407 106.6 10.4 87
1994 Jul 11 00 14 10 59.76 -12 18 13.2 5.036 5.408 106.2 10.4 81
1994 Jul 11 12 14 11 07.52 -12 17 57.8 5.044 5.408 105.7 10.4 74
1994 Jul 12 00 14 11 15.59 -12 17 41.8 5.051 5.409 105.3 10.4 68
1994 Jul 12 12 14 11 23.99 -12 17 25.0 5.059 5.409 104.8 10.5 61
1994 Jul 13 00 14 11 32.75 -12 17 07.1 5.067 5.410 104.4 10.5 54
1994 Jul 13 12 14 11 41.89 -12 16 47.7 5.075 5.411 103.9 10.5 47
1994 Jul 14 00 14 11 51.46 -12 16 26.3 5.083 5.411 103.5 10.5 40
1994 Jul 14 12 14 12 01.53 -12 16 02.1 5.091 5.412 103.1 10.5 34
1994 Jul 15 00 14 12 12.18 -12 15 33.8 5.099 5.413 102.6 10.6 27
1994 Jul 15 12 14 12 23.59 -12 14 59.4 5.108 5.414 102.2 10.6 20
1994 Jul 16 00 14 12 36.07 -12 14 14.1 5.116 5.415 101.7 10.6 13
1994 Jul 16 12 14 12 50.47 -12 13 04.2 5.124 5.416 101.3 10.6 6
Ephemeris (with perturbations) for Comet S-L 9, fragment Q1
Date (UT) h R.A. J2000 Dec. Delta r Theta Beta Moon
1994 Jul 5 00 14 09 19.40 -12 24 49.7 4.941 5.398 111.5 10.1 156
1994 Jul 5 12 14 09 23.82 -12 24 36.0 4.949 5.398 111.1 10.1 150
1994 Jul 6 00 14 09 28.44 -12 24 22.9 4.956 5.399 110.6 10.2 144
1994 Jul 6 12 14 09 33.28 -12 24 10.4 4.964 5.399 110.2 10.2 138
1994 Jul 7 00 14 09 38.32 -12 23 58.4 4.971 5.399 109.7 10.2 132
1994 Jul 7 12 14 09 43.57 -12 23 47.1 4.979 5.400 109.2 10.2 126
1994 Jul 8 00 14 09 49.03 -12 23 36.3 4.986 5.400 108.8 10.3 119
1994 Jul 8 12 14 09 54.70 -12 23 25.9 4.994 5.401 108.3 10.3 113
1994 Jul 9 00 14 10 00.59 -12 23 16.1 5.001 5.401 107.9 10.3 107
1994 Jul 9 12 14 10 06.70 -12 23 06.8 5.009 5.401 107.4 10.3 100
1994 Jul 10 00 14 10 13.03 -12 22 57.8 5.017 5.402 107.0 10.4 94
1994 Jul 10 12 14 10 19.58 -12 22 49.3 5.024 5.402 106.5 10.4 87
1994 Jul 11 00 14 10 26.36 -12 22 41.1 5.032 5.403 106.1 10.4 81
1994 Jul 11 00 14 10 26.36 -12 22 41.1 5.032 5.403 106.1 10.4 81
1994 Jul 11 12 14 10 33.36 -12 22 33.2 5.040 5.403 105.6 10.4 74
1994 Jul 12 00 14 10 40.60 -12 22 25.6 5.048 5.403 105.2 10.5 67
1994 Jul 12 12 14 10 48.08 -12 22 18.2 5.055 5.404 104.7 10.5 61
1994 Jul 13 00 14 10 55.80 -12 22 10.9 5.063 5.404 104.3 10.5 54
1994 Jul 13 12 14 11 03.77 -12 22 03.7 5.071 5.405 103.8 10.5 47
1994 Jul 14 00 14 11 12.00 -12 21 56.5 5.079 5.405 103.4 10.5 40
1994 Jul 14 12 14 11 20.50 -12 21 49.1 5.087 5.406 102.9 10.6 33
1994 Jul 15 00 14 11 29.27 -12 21 41.5 5.095 5.406 102.5 10.6 27
1994 Jul 15 12 14 11 38.32 -12 21 33.6 5.103 5.407 102.0 10.6 20
1994 Jul 16 00 14 11 47.68 -12 21 25.0 5.111 5.408 101.6 10.6 13
1994 Jul 16 12 14 11 57.36 -12 21 15.7 5.119 5.408 101.2 10.6 6
1994 Jul 17 00 14 12 07.39 -12 21 05.3 5.127 5.409 100.7 10.6 3
1994 Jul 17 12 14 12 17.79 -12 20 53.4 5.135 5.410 100.3 10.7 9
1994 Jul 18 00 14 12 28.61 -12 20 39.5 5.143 5.410 99.8 10.7 16
1994 Jul 18 12 14 12 39.91 -12 20 22.9 5.151 5.411 99.4 10.7 23
1994 Jul 19 00 14 12 51.78 -12 20 02.3 5.159 5.412 99.0 10.7 30
1994 Jul 19 12 14 13 04.38 -12 19 35.7 5.168 5.413 98.5 10.7 37
1994 Jul 20 00 14 13 18.01 -12 18 58.9 5.176 5.414 98.1 10.7 44
1994 Jul 20 12 14 13 33.45 -12 17 58.9 5.185 5.415 97.7 10.7 51
Ephemeris (with perturbations) for Comet S-L 9, fragment W
Date (UT) h R.A. J2000 Dec. Delta r Theta Beta Moon
1994 Jul 5 00 14 09 09.71 -12 26 02.8 4.940 5.397 111.5 10.1 156
1994 Jul 5 12 14 09 14.04 -12 25 50.0 4.948 5.397 111.1 10.1 150
1994 Jul 6 00 14 09 18.56 -12 25 37.9 4.955 5.397 110.6 10.2 144
1994 Jul 6 12 14 09 23.29 -12 25 26.4 4.963 5.398 110.1 10.2 138
1994 Jul 7 00 14 09 28.22 -12 25 15.5 4.970 5.398 109.7 10.2 132
1994 Jul 7 12 14 09 33.36 -12 25 05.2 4.978 5.398 109.2 10.2 126
1994 Jul 8 00 14 09 38.70 -12 24 55.5 4.985 5.399 108.8 10.3 119
1994 Jul 8 12 14 09 44.24 -12 24 46.4 4.993 5.399 108.3 10.3 113
1994 Jul 9 00 14 09 50.00 -12 24 37.9 5.000 5.399 107.8 10.3 107
1994 Jul 9 12 14 09 55.96 -12 24 29.8 5.008 5.400 107.4 10.4 100
1994 Jul 10 00 14 10 02.14 -12 24 22.3 5.016 5.400 106.9 10.4 94
1994 Jul 10 12 14 10 08.53 -12 24 15.3 5.023 5.400 106.5 10.4 87
1994 Jul 11 00 14 10 15.14 -12 24 08.7 5.031 5.401 106.0 10.4 81
1994 Jul 11 12 14 10 21.97 -12 24 02.6 5.039 5.401 105.6 10.4 74
1994 Jul 12 00 14 10 29.02 -12 23 56.8 5.046 5.402 105.1 10.5 67
1994 Jul 12 12 14 10 36.29 -12 23 51.4 5.054 5.402 104.7 10.5 61
1994 Jul 13 00 14 10 43.79 -12 23 46.3 5.062 5.403 104.2 10.5 54
1994 Jul 13 12 14 10 51.53 -12 23 41.5 5.070 5.403 103.8 10.5 47
1994 Jul 14 00 14 10 59.50 -12 23 36.8 5.078 5.404 103.3 10.5 40
1994 Jul 14 12 14 11 07.71 -12 23 32.3 5.086 5.404 102.9 10.6 33
1994 Jul 15 00 14 11 16.17 -12 23 27.8 5.094 5.404 102.4 10.6 27
1994 Jul 15 12 14 11 24.88 -12 23 23.3 5.101 5.405 102.0 10.6 20
1994 Jul 16 00 14 11 33.86 -12 23 18.7 5.109 5.406 101.6 10.6 13
1994 Jul 16 12 14 11 43.11 -12 23 13.8 5.117 5.406 101.1 10.6 6
1994 Jul 17 00 14 11 52.65 -12 23 08.6 5.125 5.407 100.7 10.6 3
1994 Jul 17 12 14 12 02.48 -12 23 02.7 5.133 5.407 100.2 10.7 9
1994 Jul 18 00 14 12 12.63 -12 22 56.1 5.141 5.408 99.8 10.7 16
1994 Jul 18 12 14 12 23.13 -12 22 48.4 5.149 5.409 99.4 10.7 23
1994 Jul 19 00 14 12 34.00 -12 22 39.2 5.158 5.409 98.9 10.7 30
1994 Jul 19 12 14 12 45.28 -12 22 28.1 5.166 5.410 98.5 10.7 37
1994 Jul 20 00 14 12 57.04 -12 22 14.2 5.174 5.411 98.1 10.7 44
1994 Jul 20 12 14 13 09.36 -12 21 56.4 5.182 5.412 97.6 10.7 52
1994 Jul 21 00 14 13 22.41 -12 21 32.6 5.191 5.413 97.2 10.7 59
1994 Jul 21 12 14 13 36.46 -12 20 58.7 5.199 5.414 96.8 10.7 66
1994 Jul 22 00 14 13 52.31 -12 20 02.1 5.208 5.415 96.3 10.7 73
Predicted length of train of fragments
Due to the different gravitational pull in the individual fragments,
the length of the train will increase with time. The increase is most
rapid just before the impacts.
Date Angular length Physical length
(arcsec) (km)
1993 Mar 25 49 158,000
Jul 1 67 265,000
1994 Jan 1 131 584,000
Feb 1 161 669,000
Mar 1 200 762,000
Apr 1 255 893,000
May 1 319 1,070,000
Jun 1 400 1,366,000
Jul 1 563 2,059,000
Jul15 944 3,593,000
Impact A 1286 4,907,000
4.2 Jupiter and its moons.
Jupiter is the largest planet in the solar system. It is one of the
brightest natural objects in the sky (only the Sun, the Moon and Venus
are brighter) and it has always been known by mankind. Galileo Galilei
first pointed his new telescope towards Jupiter in January 1610 and
immediately discovered the four major moons, Io, Europa, Ganymedes and
Callisto. Continued astronomical observations have shown that Jupiter
possesses at least 16 moons. Jupiter is also known to have a rather
faint ring of dust particles, much less conspicuous than the one
around Saturn.
Jupiter is 318 times heavier than the Earth and about 1000 times
lighter than the Sun. It is now clear that Jupiter has about the same
composition as the Sun (mostly hydrogen and helium) and that it is
actually a "failed" star.
When the solar system was created about 4,600 million years ago by
contraction in an interstellar cloud of gas and dust, the young Sun
emerged after a few million years at the center of a rotating disk of
this material. The temperature inside the Sun rose rapidly and soon
reached several million degrees, enough to ignite the atomic
processes, mostly the transformation of hydrogen into helium, that now
are responsible for the brightness and the enormous energy output from
the Sun. Contrarily, Jupiter began as a much smaller concentration of
matter in the outer part of the disk and due to its small mass, the
contraction process never resulted in temperatures high enough to
start chain reactions inside Jupiter.
As far as is known, Jupiter (like the Sun) has no solid surface, and
its apparent surface is simply the top layer of the clouds in its
atmosphere. There are three cloud layers; the uppermost one consists
of ammonium particles, the next lower one of more complex ammonium and
nitrogen compounds, while the lowest one is made up of frozen water
particles (ice crystals). There may be other layers below these which
are still unknown to us.
Next to nothing is known about Jupiter's inner structure. It is
conceivable that there are specific and well-defined layers of
different composition similar to those in the Earth. Some models
predict a central core of helium, surrounded by a shell of "metallic"
hydrogen (a highly exotic state of this basic element which can only
exist at extremely high pressures).
Jupiter's moons come in many different sizes. While the four major
ones are as big as, or bigger than our own Moon, all of the others are
significantly smaller and are most likely captured asteroids.
The moon Io is of particular interest; there are many active volcanoes
on its surface which emit mostly sulphuric compounds. This activity is
due to Jupiter's incessant gravitational pull in Io, which deposits
much energy in its inner parts and thereby causes a heating effect.
Some Jupiter Data
Mean distance from the Sun 778.3 million km
Orbital period around the Sun 11.86 years
Mean orbital velocity 13.06 km/sec
Orbital inclination to Ecliptica 1.30 degrees
Mass 1.9 10^27 kg (= 318 x Earth mass)
Mass (relative to the Sun) 1/1047
Equatorial radius 71,600 km (= 11.23 x Earth radius)
Mean density 1.314 kg/m^3
Rotation period 9 hr 50 min
The moons of Jupiter
Name Distance from Jupiter Orbital period Radius
Metis 127,000 km 0.295 days ~20 km
Adrasteia 128,000 km 0.297 days 12 km
Amalthea 181,000 km 0.489 days 135 km
Thebe 221,000 km 0.670 days 55 km
Io 422,000 km 1.77 days 1826 km
Europa 671,000 km 3.55 days 1563 km
Ganymedes 1,070,000 km 7.16 days 2638 km
Callisto 1,880,000 km 16.7 days 2410 km
Leda 11,100,000 km 240 days ~5 km
Himalia 11,500,000 km 251 days ~90 km
Lysithea 11,700,000 km 260 days ~10 km
Elara 11,700,000 km 260 days ~40 km
Ananke 20,700,000 km 617 days ~10 km
Carme 22,400,000 km 692 days ~15 km
Pasiphae 23,300,000 km 735 days ~20 km
Sinope 23,700,000 km 758 days ~15 km
The outermost four moons move in retrograde orbits, that is contrary
to the motion of almost all other objects in the solar system.
Jupiter's position in the sky
Explanation of Symbols:
R.A. J2000 Dec. = Geocentric astrometric right ascension and declination
referred to the mean equator and equinox of J2000.
Light time corrections have been applied.
Delta = Geocentric distance in AU.
r = Heliocentric distance in AU.
Angular size = The angular size of Jupiter's disk in arcseconds
Date (0 UT) R.A. J2000 Dec. Delta r Angular size
1994 Jul 4 14 11.9 -12:01 4.9412 5.4192 40
1994 Jul 5 14:11.9 -12:02 4.9554 5.4190 40
1994 Jul 6 14:11.9 -12:02 4.9697 5.4188 40
1994 Jul 7 14:12.0 -12:03 4.9841 5.4187 39
1994 Jul 8 14:12.0 -12:03 4.9986 5.4185 39
1994 Jul 9 14:12.1 -12:04 5.0132 5.4183 39
1994 Jul 10 14:12.2 -12:05 5.0278 5.4181 39
1994 Jul 11 14:12.3 -12:05 5.0426 5.4180 39
1994 Jul 12 14:12.4 -12:06 5.0574 5.4178 39
1994 Jul 13 14:12.5 -12:07 5.0722 5.4176 39
1994 Jul 14 14:12.6 -12:08 5.0872 5.4174 39
1994 Jul 15 14:12.8 -12:09 5.1021 5.4172 39
1994 Jul 16 14:12.9 -12:10 5.1172 5.4170 38
1994 Jul 17 14:13.1 -12:11 5.1323 5.4169 38
1994 Jul 18 14:13.2 -12:12 5.1474 5.4167 38
1994 Jul 19 14:13.4 -12:14 5.1626 5.4165 38
1994 Jul 20 14:13.6 -12:15 5.1778 5.4163 38
1994 Jul 21 14:13.8 -12:16 5.1930 5.4161 38
1994 Jul 22 14:14.0 -12:18 5.2083 5.4159 38
1994 Jul 23 14:14.2 -12:19 5.2236 5.4158 38
4.3 Predicted impact times and visibility from different sites
The following table was prepared by Paul Chodas and Don Yeomans
(JPL/Caltech) and gives the predicted impact times, based on orbital
computations, taken into account all available observations up to July
5. It is expected that further observations will reduce the indicated
uncertainties substantially.
The predictions for fragments E, G, H, K, L, Q, R, S, and W are the
most accurate, as these have the best-known orbits; fragments T, U,
and V have the most poorly-determined orbits, (especially U).
The indicated "Earth Receive" times correspond to the moments when the
events become observable from the Earth; the light travel time from
Jupiter (about 43 minutes) has been taken into account. The
uncertainties indicate the interval around the predicted moment during
which there is an approx. 95 % chance that the event really happens.
The best viewing conditions for each impact are indicated. Note,
however, that they are significantly better from locations in the
southern hemisphere than from the mentioned northern sites.
----------------------------------------------------------------------------------------
Fragment Earth Receive Uncert. Best viewing conditions from
Date /Time interval
July (UT) (+-min)
-----------------h--m--s-----------------------------------------------------------------
A = 21 16 19:53:40 17 Africa (except W. Africa), Middle East, Eastern Europe
B = 20 17 02:49:03 17 Eastern N. America, Mexico, Western S. America
C = 19 17 06:55:36 17 New Zealand, Hawaii
D = 18 17 11:41:50 17 Australia, New Zealand, Japan
E = 17 17 15:03:51 16 India, Southern China, S.E. Asia, Western Australia
F = 16 18 00:28:15 14 S. America
G = 15 18 07:28:00 11 New Zealand, Hawaii
H = 14 18 19:25:48 11 Africa (except W. Africa), Middle East, Eastern Europe
K = 12 19 10:17:58 12 Australia, New Zealand
L = 11 19 22:06:58 12 Brazil, W. Africa, Spain
N = 9 20 10:18:37 17 Australia, New Zealand
P2= 8b 20 15:05:10 14 India, Southern China, S.E. Asia, Western Australia
Q2= 7b 20 19:31:36 25 Africa (except W. Africa), Middle East, Eastern Europe
Q1= 7a 20 19:59:04 14 Africa (except W. Africa), Middle East, Eastern Europe
R = 6 21 05:22:04 14 Hawaii, West coast N. America
S = 5 21 15:07:13 12 India, Southern China, S.E. Asia, Western Australia
T = 4 21 18:04:14 30 Africa (except W. Africa), Middle East, Eastern Europe
U = 3 21 21:47:00 32 Brazil, W. Africa, Spain
V = 2 22 03:57:25 24 Western U.S.A., Mexico
W = 1 22 07:53:17 18 New Zealand, Hawaii, Eastern Australia
----------------------------------------------------------------------------------------
The difference in viewing conditions from the North and the South is
illustrated by the following table. The altitude is the height (in
degrees) of Jupiter in the sky above the horizon; the higher, the less
the atmosphere will disturb astronomical observations.
Munich, Germany La Silla, Chile
Geographical latitude +48 -30
Jupiter maximal altitude after sunset 27 73
Time between sunset and Jupiter set 3 hrs 55 min 7 hrs 45 min
4.4 List of expected effects
The fragments will deposit a large amount of energy in the Jupiter
atmosphere when they burn up and explode at the impact. Many different
phenomena may result.
The following list summarizes the supposedly most important effects,
their probable duration and how they may be observed. It should be
stressed that it is very uncertain how strong these effects will
actually be and therefore how easy or difficult it will be to observe
them.
Effect Duration Type of Observation
Ablation Flash few seconds Reflection from satellite/ring
Rising Plume 1 - 2 hours Changes of atmospheric patterns
Spectral changes (new molecules ?)
Sonic waves several hours Temperature increase (ring pattern)
Oscillations several days Temperature variations
Dust charging several days Magnetic field => Radio emission
changes
Changes in Io torus
Dust => Ring ~10 days Changes in dust ring
Dust in atmosphere some days Changes in colour of atmospheric
patterns
4.5 Ground- and space based observations
There will be many different types of observations from the ground and
from space. In general, they complement each other. Only by observing
this unique event with the entire arsenal of modern astronomical
equipment can we hope to obtain a satisfactory understanding of the
associated phenomena.
The following main types of observations are planned from the ground:
- Accurate pre-impact astrometry (positions) of the individual comet fragments
- Search for differences in the optical emission of the individual fragments
- Imaging and surface polarimetry of the cometary dust
- Fabry-Perot-interferometry of the gas in the comet fragments
- High-speed photometry of light echoes on the moons and the ring
from the impacts
- Observations in the visual and infrared wavebands of Jupiter's surface
after the impacts (imaging, spectroscopy)
- Visual and infrared imaging of the Io Plasma Torus
- Millimeter observations of post-impact molecules
- Radio monitoring of (decametric) emission
and from space:
- HST: Ultraviolet + visual high-resolution imaging
Ultraviolet spectroscopy
- Galileo: Imaging of impact sites
Infrared mapping
Radio monitoring
- Voyager 2: Radio monitoring
- Ulysses: Radio monitoring
4.6 Participating observatories
It is expected that virtually all major observatories in the world
will participate in observations of this event, with the exception of
the northenmost ones from where Jupiter is not well observable because
of very low altitude above the horizon and the short summer nights.
Since it is winter and the nights are long on the southern hemisphere
and Jupiter will be 12 degrees south of the celestial equator, the
observing conditions are best for the astronomical observatories
located here, including the ESO La Silla observatory.
In addition to the major southern observatories, ESO La Silla, the
Cerro Tololo Interamerican Obervatory (both located in Chile), the
Anglo-Australian Observatory (Siding Spring, Australia), the South
African Aastronomical Observatory (Sutherland, South Africa), the main
participating observatories are in the southern part of the United
States of America (Kitt Peak National Observatory, the Palomar
Observatory, the Mauna Kea Observatory), in Spain (La Palma, Calar
Alto), Japan, China, India, Mexico, and in the CIS republics.
Observations are also planned from the South Pole and with the
high-altitude Kuiper Airborne Observatory over the South Pacific.
4.7 International coordination
As soon as it became clear in the autumn of 1993 that a collision
between comet Shoemaker-Levy 9 Jupiter will indeed take place,
astronomers from many countries began to plan the associated
observational campaign. International coordination and rapid exchange
of information between observers and theoreticians is of particular
importance during such a campaign where unexpected events may happen
and quick adjustment of the observing programmes is desirable.
The astronomers are connected in various ways, but above all through
the world-wide net of computer connections; here the "Internet"
network plays the most important role. At various observatories and
institutes "mail exploders" have been set up which automatically
multiplies and sends on incoming messages to all subscribers. One of
these, at the University of Maryland, serves all observers all over
the world. Moreover, several institutions have set up "World-Wide-Web
Portals" which provide easy and efficient access to new information,
both text and images.
Since there will only be a few hours observing time at each
observatory, it is very important that new developments are passed on
to those observers who are next in the line. For instance, the first
impact will be best observable in South Africa, while the next one, a
few hours later, will be very well placed for observations from South
America.
For this reason, the observers at the South African Astronomical
Observatory at Sutherland will be in direct contact with those at
ESO's La Silla observatory in Chile. They will in turn talk to those
at Hawaii and Australia, who begin their observations when Jupiter
approaches the horizon in Chile.
5. ESO and observations at La Silla
A major coordinated programme to observe the impact of comet
Shoemaker-Levy 9 on Jupiter has begun at the ESO observatory at La
Silla in the Atacama desert (Chile). This section contains detailed
information about the ESO organisation and these programmes.
5.1 The European Southern Observatory
Some facts about ESO:
- Intergovernmental Scientific Organization, supported by 8 members
countries: Belgium, Denmark, France, Federal Republic of Germany,
Italy, the Netherlands, Sweden, Switzerland; Portugal associated since
1990. Other countries may join soon.
- Headquarters at Garching near Munich (Germany)
- Office of the Director General; Administration
- VLT and Science Divisions
- Space Telescope/European Coordinating Facility (ESA/ESO)
- Image Processing Center (MIDAS, IHAP)
- Remote Control Center (for three telescopes at La Silla)
- Astronomical Observatory at La Silla in the Southern Atacama desert (Chile)
- 2400 m altitude
- More than 290 clear nights per year
- 14 optical telescopes up to 3.6 m diameter
- 15 m submillimetre telescope (SEST)
- Full remote control from Europe of three telescopes
- 800 square km property for light and dust protection
- Future VLT Observatory at Paranal in the Central Atacama desert (Chile)
- 2660 m altitude
- More than 330 clear nights per year
- Now under development
- 725 square km property for light and dust protection
- Main Telescope Projects
- 3.5-metre New Technology Telescope (NTT); entered into operation
in late 1989
- 16-m Very Large Telescope (VLT); under construction (1988 - 2000+)
- ESO's Legal Basis, Membership, Budget, etc.
- 1962: Convention for the Establishment of ESO (with Financial Protocol)
- 1964: Agreement between Government of Chile and ESO
- 1974: Protocol of Privileges and Immunities of ESO
- 1979: Headquarters Agreement between the Federal Republic of Germany
and ESO
- Council and various Committees:
- Annual budget approx. 123 million DEM (1994); hereof about 65 million
DEM for the VLT
- about 300 staff members in Germany and Chile
- Information from ESO published in Annual Reports, The ESO
Messenger (4 times a year), Press Releases, Scientific and Technical
Notes and Preprints, Conference Proceedings, etc.
5.2 Observation Programmes at the ESO La Silla Observatory
The following table provides an overview of the planned observational
programmes at the ESO La Silla observatory (as of July 5, 1994). They
are listed according to the type of investigation and some of them
have already been successfully carried out.
More detailed information about the others, especially those during
the critical period from July 16 - 22, 1994, will be found in section
5.3.
Program no. Telescope Instrument Dates No. Allocation
Title
PI Observer(s)
------------------------------------------------------------------------------
1 ESO 1.52m B&C spec. Apr. 12 - Apr. 15 3 ESO
Spectroscopy of individual SL9 nuclei
Heike Rauer Heike Rauer
Max-Planck-Institut fuer Aeronomie
D-37189 Katlenburg-Lindau
Max-Planck-Str. 2
Germany
Tel.: +49-5556-979-394
Fax.: +49-5556-979-240
email: rauer@linax1.dnet.gwdg.de
-------------------------------------------------------------------------------
2 NTT EMMI June 30 - July 2 2 ESO
Direct imaging and spectroscopy of individual SL9 nuclei
Rita Schulz Rita Schulz
Max-Planck-Institut fuer Aeronomie Joachim A. Stuewe
Postfach 20
D-37189 Katlenburg-Lindau
Germany
Tel.: +49-5556-979-219
Fax.: +49-5556-979-240
email: schulz@linax1.dnet.gwdg.de
-------------------------------------------------------------------------------
3 2.2m Foc. Red. MPAe Apr. 1 - 7 6 MPIA
Narrow-band Fabry-Perot interferometry and imaging of the Io torus
Klaus Jockers Klaus Jockers
Max-Planck-Institut fuer Aeronomie (MPAe)
Postfach 20
D-37189 Katlenburg-Lindau
Germany
Tel.: +49-5556-979-293
Fax.: +49-5556-979-240
email: jockers@linmpi.dnet.gwdg.de
-------------------------------------------------------------------------------
4 1m Foc. Red. MPAe Apr. 25 - May 1 6 ESO
Narrow-band (Fabry-Perot) and wide-band imaging of comet SL 9
Klaus Jockers Klaus Jockers
Max-Planck-Institut fuer Aeronomie (MPAe)
Postfach 20
D-37189 Katlenburg-Lindau
Germany
Tel.: +49-5556-979-293
Fax.: +49-5556-979-240
email: jockers@linmpi.dnet.gwdg.de
-------------------------------------------------------------------------------
5 DK 1.54 m CAM/CCD Apr. 30 - Jul 15? ? x 1hour ESO/DK
Astrometry of individual SL-9 nuclei
Olivier Hainaut Olivier Hainaut
European Southern Observatory
Karl-Schwarzschild-Strasse 2
D-81827 Garching bei Muenchen
Germany
Tel. : +4989-32006306
Fax : +4989-3202362
email: ohainaut@eso.org
-------------------------------------------------------------------------------
6 1 m Special July 15 - July 25 10 ESO
Fast multi-channel UBVRI photometry of Jovian satellites
Heinz Barwig Heinz Barwig
Universitaets-Sternwarte Muenchen Otto Baernbantner
Scheinerstr. 1
D-81679 Muenchen
Germany
Tel.: +49-89-922094-45
Fax.: +49-89-922094-27
email: hbarwig@usm.uni-muenchen.de
-------------------------------------------------------------------------------
7 DK 1.54 m Spec/CCD July 17 - July 24 8 ESO
Fast CCD photometry of the satellites and CCD imaging of Jupiter's disk
Bruno Sicardy Laurent Jorda
Observatoire de Paris-Meudon
5, place Jules Janssen
F-92195 Meudon Cedex
France
Tel.: +33-1-4507-7962
Fax.: +33-1-4507-7469
email: sicardy@mesiob.obspm.circe.fr
-------------------------------------------------------------------------------
8 Boch. 60cm CCD July 10 - July 25 15 Bochum
CCD imaging of Jupiter
Uri Carsenty Uri Carsenty
DLR S. Mottola
NE-PE E. Bratz
D-82234 Wesling
Germany
Tel.: +49-8153-281328
Fax.: +49-8153-2467
email: "28842::carsenty"@mc0.hq.eso.org
carsenty@mars.pe.op.dlr.de
-------------------------------------------------------------------------------
9 Dutch 90cm CCD 16-22 July 4 x 1/2 night Dutch
CCD imaging of Jupiter
Keith Horne Keith Horne
Astronomical Institute Remco Shoemakers
Postbus 80000
NL-3508 TA Utrecht
The Netherlands
Tel. : +30-31-535234
Fax : +30-31-535201
email: horne@fys.ruu.nl
-------------------------------------------------------------------------------
10 CAT 1.4m CES July 18 - July 25 7 ESO
High-resolution spectra of Jupiter (detection of water vapour)
Anne Marie Lagrange Anne Marie Lagrange
Laboratoire d'Astrophysique Olivier Hainaut
Observatoire de Grenoble
414, rue de la Piscine
F-38041 Grenoble Cedex
France
Tel. : +33-76514788
Fax : +33-76448821
email: lagrange@gag.observ-gr.fr
-------------------------------------------------------------------------------
11 2.2m IRAC2B July 16 - 24 8 MPIA
Near-IR imaging of comet SL 9 and Jupiter's atmosphere
Klaus Jockers Klaus Jockers
Max-Planck-Institut fuer Aeronomie
Postfach 20
D-37189 Katlenburg-Lindau
Germany
Tel.: +49-5556-979-293
Fax.: +49-5556-979-240
email: jockers@linmpi.dnet.gwdg.de
-------------------------------------------------------------------------------
12 NTT IRSPEC July 16 - July 28 12 x 1/2 ESO
July 30 - July 31 1 x 1/2 ESO
Near-IR spectroscopy of Jupiter
Therese Encrenaz Therese Encrenaz,
DESPA - Observatoire de Paris Guenter Wiedemann
F-92195 Meudon
France
Tel.: +33-1-4507-7691
Fax.: +33-1-4507-2806
email: "meudon::encrenaz"@mc0.hq.eso.org
-------------------------------------------------------------------------------
13 NTT IRSPEC July 16 - July 28 12 x 1/2 ESO
July 30 - July 31 1 x 1/2 ESO
Near-IR spectroscopy of Jupiter
Rita Schulz Rita Schulz
Max-Planck-Institut fuer Aeronomie Joachim A. Stuewe
Postfach 20
D-37189 Katlenburg-Lindau
Germany
Tel.: +49-5556-979-219
Fax.: +49-5556-979-240
email: schulz@linax1.dnet.gwdg.de
-------------------------------------------------------------------------------
14 3.6 m TIMMI July 16 - July 28 12 x 1/2 ESO
July 30 - July 31 1 x 1/2 ESO
Far-IR imaging and spectroscopy of Jupiter (atmosphere)
Timothy A. Livengood Tim Livengood
NASA/Goddard Space Flight Center Theodor Kostiuk
NASA/GSFC Hans Ulrich Kauefl
Code 693
Greenbelt, MD 20771
USA
Tel. : +1-301-286-1552
Fax : +1-301-286-1629
email: ystal@lepvax.gsfc.nasa.gov
-------------------------------------------------------------------------------
15 3.6 m TIMMI July 16 - July 28 12 x 1/2 ESO
July 30 - July 31 1 x 1/2 ESO
Far-IR imaging and spectroscopy of Jupiter (seismology)
Benoit Mosser Benoit Mosser
Institut d'Astrophysique Pierre O. Lagage
98, bd. Arago
F-75014 Paris
France
Tel. : +33-1-4320-1425
Fax : +33-1-4329-8673
email: mosser@iap.fr
-------------------------------------------------------------------------------
16 DK 1.54 m Spec/CCD July 17 - July 24 8 ESO
CCD imaging of Io torus and Jupiter ring
Nicolas Thomas Nicolas Thomas
Max-Planck-Institut fuer Aeronomie
Max-Planck-Str. 2
D-37189 Katlenburg-Lindau
Germany
Tel. : +49-5556-979-437
Fax : +49-5556-979-240 or 141
email: thomas@linmpi.dnet.mpae.de
-------------------------------------------------------------------------------
17 SEST 350 GHz July 18 - July 23 5 shifts ESO
Molecular lines
Daniel Gautier Pierre Colom
Observatoire de Paris-Meudon Dominique Bockelee-Morvan
Observatoire de Meudon Didier Despois
F-92195 Meudon
France
Tel. : +33-1-4507-7707
Fax. : +33-1-4507-7469
email: gautierd@mesiob.obspm.circe.fr
-------------------------------------------------------------------------------
Explanation:
Program no.: La Silla SL9/Jupiter Program No.
Telescope : Telescope allocated
Instrument : Instrumental configuration
Dates : Time allocated (noon to noon for optical telescopes)
No. : Nos. of nights (optical telescopes) or shifts (SEST)
Allocation : Time allocation authority
PI : Name and address of Principal Investigator
Observer(s): Name(s) of observer(s)
Title : Brief description of the purpose of this program
-------------------------------------------------------------------------------
5.3 Brief descriptions of individual programmes at La Silla
The following descriptions of the programmes which will be carried out
at La Silla have been prepared by the participating astronomers.
The programme numbers refer to the table in section 5.2, which also
list the addresses of the Prinicipal Investigators, as well as the
names of the observers who are expected to be at La Silla. The
acronyms used are explained in section 1.2.
As experience will be gained from the first impacts, it cannot be
excluded that some of the indicated observational procedures and goals
will be adjusted in the course of this campaign.
Programmes 2 and 13
--------------------
INFRARED OBSERVATIONS OF COMET SHOEMAKER-LEVY 9 AND THE IMPACT SITES
3.5-metre New Technology Telescope with the EMMI and IRSPEC instruments
June 30 - July 02, 1994 (Programme 2)
July 16 - July 28, 1994 (Programme 13)
July 30 - July 31, 1994 (Programme 13)
Rita Schulz (Max-Planck-Institute fuer Aeronomie, Katlenburg-Lindau,
Germany; PI)
We shall monitor the individual fragments of comet Shoemaker-Levy 9
with the NTT in different spectral ranges before (June 30 - July 2,
1994) and during their impacts on Jupiter (July 16 - 28, 1994).
The colour and the spatial distribution of the dust that surrounds the
individual fragments will be analysed by means of CCD images taken in
the visual range with different filters; this may uncover possible
differences between the individual fragments. At the same time, we
will also obtain spectra of the fragments to search for emission bands
of the various gaseous species which are normally present in comets.
Near-infrared spectroscopical monitoring of the impacts will provide
information about the composition of the individual fragments of the
comet. It is expected that large amounts of water will be
released. Ion chemistry calculations thereby predicts the formation of
several ions which can be observed in the near-IR.
Moreover, the effects of Jupiter's magnetosphere on the cometary dust
will be analysed in detail on images obtained in wavebands that
correspond to one of the methane absorption bands, both in late June
and during the week of the impacts.
Programme 5
-----------
ACCURATE POSITIONS OF THE INDIVIDUAL COMET FRAGMENTS
Danish 1.5-metre telescope with a CCD camera (and other telescopes)
April 30 - July 15, 1994 (intermittently)
Olivier Hainaut (ESO; PI) and Richard M. West (ESO)
The individual fragments of comet Shoemaker-Levy 9 move in very
complex orbits around Jupiter. They are mainly influenced by the
gravitational pull of the Sun and Jupiter, and to some extent by the
moons of this giant planet. During the last few days before the
impacts, the fragments will experience a rapid acceleration to about
60 km/sec; this is, however, strongly dependent on their actual
locations relative to Jupiter and unless the orbits are extremely well
known, it is therefore difficult to make very accurate predictions of
the impact times.
The determination of these orbits is based on positional measurements
of the individual fragments at different times. This is done by means
of images obtained with large telescopes and sensitive CCD cameras.
The positions of the comet fragments are compared with those of stars
with accurately known positions, that are seen on the same images.
In order to know in advance as well as possible when the impacts
occur, it is necessary to continue astrometric observations up to the
very last moment, in practice a few days, perhaps the last day, before
the first impact. However, such observations are difficult for
several reasons.
First, when the fragments are very close to Jupiter, the strong
straylight from the planet will flood the CCD camera and make it
difficult to see the images of the fainter ones. Next, the fragments
are moving away from each other and already the "string of pearls" is
so long that several exposures are necessary to image them all. And
most important, in order to achieve the highest possible accuracy, the
positions of the fragments must be compared with those of stars with
very well determined positions ("astrometric standards") of which
there are so few in the sky that none can be expected to be located on
the same exposures as the comet. This problem is overcome by first
measuring the accurate positions of some of the fainter stars seen on
the CCD images with the comet on available large-field photographic
plates which also show some of the astrometric standard stars.
We have begun such measurements and thanks to the kind help of the
scientists involved in the ESA Hipparcos programme, we have obtained
pre-publication lists of extremely accurate astrometric standards near
the comet path across the sky. This has enabled us to mesure the
positions of all the fragments of comet Shoemaker-Levy 9 with high
precision (0.2 - 0.3 arcseconds, corresponding to about 200 kilometres
near Jupiter) and herewith to contribute substantially to the
improvement of the prediction of the impact times.
Programme 6
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SEARCH FOR LIGHT ECHOES FROM THE IMPACTS
1-meter telescope with multi-channel high-speed photometer
July 15 - 25, 1994
Heinz Barwig (PI), Hermann Boehnhardt, Karl-Heinz Mantel and Otto
Baernbantner (Universititaets-Sternwarte Muenchen, Germany)
We will attach the special multi-channel high-speed photometer of the
Universitaets-Sternwarte Muenchen to the ESO 1-metre telescope in
order detect light echoes from the Jovian moons. Since the impacts
themselves are not directly visible from Earth, we will use suitable
Jovian moons as mirrors behind Jupiter to reflect the flashes caused
during the entry of the comet fragments into Jupiter's atmosphere.
However, these light echoes are rather difficult to detect against the
bright sunlight also reflected from the moons' surfaces. Light echoes
from moons, which are in the shadow of Jupiter, but still visible from
the Earth, will be much easier to measure, but unfortunately only one
impact is expected to occur during such a satellite eclipse, namely
that of fragment K with Europa in eclipse.
During our observations up to three Jovian satellites will be
monitored simultaneously through broad-band filters (the standard
U,B,V,R,I-colours). The photometer works very rapidly (it provides a
temporal resolution of a tenth of a second or better) and may
therefore give a very accurate timing of the light echoes and
therefore the impacts. If the flash from an impact is reflected from
several moons, the reflected light will arrive at different times at
Earth and we will observe these time delays. In combination with the
known positions of the moons, this will allow us to calculate the actual
impact time at Jupiter.
Our multi-colour measurements will at the same time provide an estime
of the flash temperature and the energy released in the visual
wavelength range at the moment of impact.
The knowledge of the exact impact times is of particular interest,
since this will make it possible to establish reliable reference
points for the studies of the propagation of impact phenomena through
the Jovian atmosphere and for the seismic observations. Furthermore,
accurate impact times will help to select and to send back to Earth
the most interesting images obtained by the Galileo spacecraft which
has the privilege of looking directly at impacts sites on the rear
side of Jupiter.
Programme 7
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FAST CCD IMAGING AND PHOTOMETRY OF THE IMPACTS
1.54-metre Danish telescope with a special CCD camera
July 17 - 24, 1994
Bruno Sicardy (Observatoire de Paris, Meudon, France; PI), Jean
E. Arlot, F. Colas, W. Thuillot (Bureau des Longitudes, Paris,
France), C. Buil (Centre National d'Etudes Spatiales, Paris, France)
and J. Lecacheux (Observatoire de Paris, France).
Our program will make use of an anti-blooming CCD camera to monitor
some of the collisions of the fragments of comet P/S-L 9 with
Jupiter. Although the impacts will not be directly visible from the
Earth, they occur sufficiently close to the limb of Jupiter (about 10
degrees or less) so that any plume that rises a few hundred kilometres
above the impact point will be directly observable from the Earth a
few minutes after the impact.
A fast anti-blooming CCD has the advantage of being able to record up
to 2-3 images/sec, while limiting the scattered light from the bright
planet. From ESO, one of the best candidates to be observed is the
impact of fragment F just after sunset on July 17. We will try to
image the corresponding plume, in order to better estimate the exact
time of impact, and also to be able to say something about the
impactor mass and the plume formation.
Another goal of particular interest is to attempt to catch the
reflection of the impact light on the comet dust during the very entry
of the corresponding fragment. It may also be that reflections will be
observable on the small moon Amalthea. Such reflections will be very
useful for determining the exact impact times and may give information
about the first few seconds of the entry into the atmosphere.
In the few hours following the impacts (in particular L and U), we
will turn to imaging the cloud appearances at the impact points and
record the evolution of these changes as the planet settles back to
equilibrium. Various optical filters (corresponding to the continuum
light and methane absorption bands) will allow us to probe different
levels in Jupiter's atmosphere, and their respective reactions to the
impacts.
Programme 8
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CCD OBSERVATIONS OF S-L 9 AND JUPITER
Bochum 60-cm telescope with CCD camera
July 10 - 25, 1994
Uri Carsenty (PI), Stefano Mottola, Egon Bratz (DLR, Wesling, Germany)
This programme differs from most of the others at La Silla in that it
will start several days before the impacts will take place. This will
give us sufficient time to trim the instrument and to gain experience
which will be needed for the critical observations.
We intend to monitor first the comet fragments as they approach
Jupiter and later the impact zones, as they come into
view. Last-minute changes in the fragments may be detected which will
be important for the predictions of the relative strengths of the
impacts. It cannot be excluded that the strong gravitational effects
of Jupiter will lead to further disintegration of the fragments.
We shall do these observations through various optical filtres, some
of which are sensitive to the emission from the cometary dust, and
others which may show the presence of gas in the fragments, not
detected until now. Changes in the clouds of Jupiter will be seen by
comparison with images which were obtained during the preceding
days. In this way, we hope to detect the effects of the impacts as
quickly as possible and to alert other observers who may then
concentrate their observational efforts on these phenomena.
Programme 9
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CCD OBSERVATIONS OF JUPITER'S MOONS
Dutch 0.9-metre telescope with CCD camera
July 16 - 22, 1994
Keith Horne and Remco Schoenmakers (Astronomical Institute, Utrecht,
The Netherlands)
We will be using a CCD camera on the Dutch 0.9-metre telescope to take
a movie showing the brightness and color variations of one or more of
Jupiter's moons that happen to be located behind Jupiter at the times
when the largest fragments of comet Shoemaker-Levy 9 are predicted to
crash into the atmosphere on Jupiter's back side.
Since we cannot monitor the crash site directly, we will be searching
for faint traces of the crash in light that is reflected from the
moons. The predicted signature is a brief (5 second) flash in
ultraviolet and optical light as the comet fragment passes through the
transparent upper layers of the atmosphere, a short delay after it
punches through the opaque cloud deck, and finally a slower (1 minute)
pulse, first in red and then in infrared light, as the expanding and
cooling fireball from the explosion rises back up to the surface.
If we succeed in detecting these signatures, our data will allow us to
determine the temperature and surface area as functions of time during
the bolide and fireball phases. A comparison with the appropriate
model calculations will then give information about the kinetic energy
and hence the total mass of each comet fragment, its degree of
fragmentation, the depth to which it penetrates, and the vertical
structure of the Jovian atmosphere.
We plan to use a modified version of a special observing technique
that is normally used to monitor rapidly variable stars with 10 second
time resolution. During each exposure, we will set the telescope
tracking rates so that the moon's image is trailed across the CCD
detector. This trailed image will give us a record of the time
variations in the brightness of the moon. In addition, we will place
a low-dispersion prism in the filter wheel to separate the
ultraviolet, visible, red, and infrared images of the moon in a
direction perpendicular to the trailing direction. This will allow us
to determine the color and hence temperature changes as a function of
time.
When we are not monitoring the moons, we will take images of Jupiter
in various filters to record changes in the cloud features that result
from the comet impacts.
Programme 10
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DETECTION OF WATER VAPOR IN THE ATMOSPHERE OF JUPITER DURING THE IMPACTS
1.4-metre Coude Auxiliary Telescope with the Coude Echelle Spectrograph
Anne-Marie Lagrange (PI) and J.-L. Bertaux (Observatoire de Grenoble,
France), Olivier Hainaut (ESO)
We will attempt to detect water vapour in the upper atmosphere of
Jupiter above the clouds, which may be injected there during the
impact of comet fragments, either from the evaporation/fragmentation
of these fragments, or because the energy released by the impact will
result in a huge, rising plume of water vapour from the Jovian water
cloud at the 5 bar pressure level. The calculations of synthetic
spectra have shown that it may be possible to detect water vapor
absorption if there are more than 10^18 molecules/cm^2 along the line
of sight. If this amount is distributed over a square area with a side
of 3,500 km (this corresponds to one arcsec at the distance of
Jupiter), the total quantity of water would corresponds to what is
contained in an ice ball of 100 m radius. This is significantly less
than the sizes now estimated for most of the fragments and may
therefore give us a good chance of actually detecting this water.
However, it must be emphasized that the water could also come from the
clouds of Jupiter at the 5 bar pressure level, where the largest
fragments are expected to explode and send upwards a large quantity of
cometary and Jovian material.
Whatever the origin of the water vapour observed above the visible
layers of ammonia ices, it is expected that the original cloud will be
spread horizontally by the general circulation of the atmosphere. Our
spectral observations will be able to monitor the evolution of these
impact-produced water vapour clouds.
For this programme we will use the "long" camera at the CES/CAT to
obtain long-slit spectra with the CCD with a slit width of 1 arcsec at
very high spectral resolution (R = 100000, or about 0.1 nm). We shall
take high-resolution spectra of the disc of Jupiter in the
near-infrared wavelength region, where numerous strong lines of water
vapour are present. At the time of predicted impact the position of
Earth and Jupiter will be quite favorable, giving a sufficient Doppler
shift (about 26 km/sec) for the Jovian absorption lines to be well
separated from the corresponding lines from the water vapour in the
Earth's atmosphere.
Programme 11
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NEAR-INFRARED IMAGING OF JUPITER'S SURFACE
MPI/ESO 2.2-metre telescope with IRAC2B camera
July 16 - 24, 1994
Klaus Jockers (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau,
Germany; PI)
Our observations will be carried out at the MPI/ESO 2.2m telescope on
which will be mounted the ESO near-infrared camera IRAC2B. They will
be conducted in the K-band, which covers wavelengths from 2.0 to 2.4
micrometres.
Jupiter's atmosphere contains methane, which absorbs very strongly in
this wavelength range and the disk of Jupiter is therefore very dark
at this waveband. As we do not see a solid or liquid planetary surface
(if it exists at all, it must be very deep inside the planet), it is
common to measure the altitude in Jupiter's atmosphere from a
reference level, where the pressure equals the pressure at the Earth's
surface (1 bar = 10^5 Pascal = 10^5 Newton/m^2). The part of Jupiter's
atmosphere that is accessible in the K band ranges from somewhat less
than 50 km to about 400 km above this reference surface with pressures
from a few tenths to one millionth of the surface pressure at the
Earth. In the upper (outermost) part of this altitude interval, a
small but significant part of the atmosphere is ionized (the atoms and
molecules carry electric charge), so we call this region the
"ionosphere" (a similar one exists at somewhat lower altitudes in the
Earth's atmosphere).
The cometary fragments will penetrate more deeply into the atmosphere,
but this altitude range may be affected by the rising plume that is
expected to develop soon after each impact. It is unlikely that the
cometary fragments themselves will be bright enough to be observable
in the K band just before their impact, when they are close to
Jupiter's limb, but the following effects may be observable:
1. A haze cloud of cometary debris may appear above the impact site,
when it rotates to the visible side of Jupiter's disk. This cloud may
be seen in addition to the polar haze which is always present in
Jupiter's polar ionosphere.
2. We expect a modification of the Jovian polar aurora. Narrow-band
images of Jupiter, taken at wavelengths within the K-band where the
H3+ ion radiates, show a strong brightening around Jupiter's polar
caps. This is the Jovian aurora. Like the aurora observable in the
arctic and antarctic regions of the Earth, the Jovian aurora is caused
by energetic particles precipitating into the ionosphere and heating
it. A similar heating may occur after the cometary impacts. Therefore,
in addition to the always observable aurora, emission of H3+ ions
heated by the plumes that result from the cometary impacts may be
observable close to the impact sites.
3. At the longwave border of the K band, the methane absorption is
less strong and we can look more deeply into the atmosphere down to
the ammonia cloud deck at 20 km altitude. Modifications (for instance
evaporation) of the ammonia clouds by the impact may be observable.
4. The strong methane absorption present in large parts of the K band
has another advantage. As Jupiter's disk is dark, the straylight,
which affects objects outside, but close to the visible limb, is
strongly reduced. Therefore it is possible to observe in the K-band
Jupiter's faint ring that extends from 53000 to 60000 km above
Jupiter's limb. Because of the favourable relative location of the
Sun, the Earth and Jupiter during the impacts, a part of this ring (on
the side where the impacts occur) is eclipsed by Jupiter's shadow. It
may become illuminated by the light flash expected at the time of an
impact. Therefore, we shall observe the ring at the time of an impact
in order to determine the infrared characteristics of this flash.
Programme 12
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NEAR-INFRARED MONITORING OF JUPITER AT THE TIME OF THE IMPACTS
3.5-metre New Technology Telescope with IRSPEC instrument
July 16 - 28, 1994
July 30 - 31, 1994
Therese Encrenaz (PI) and P. Drossart (Observatorie de Paris, France),
Rita Schulz and J.A.Stuewe (Max-Planck-Institute fuer Aeronomie,
Katlenburg-Lindau, Germany), Guenther Wiedemann (ESO)
The impact of the fragments of comet Shoemaker-Levy 9 on Jupiter may
induce significant changes in both the troposphere and the
stratosphere of the planet, provided the fragments are big enough to
reach the level where the atmospheric pressure is 1 bar. The entire
atmospheric region located above the deep water cloud level (P about 5
bars) can be probed by near-infrared spectroscopy. In particular, the
composition and the thermal structure of the troposphere can be
studied at wavelengths around 4-5 microns, the ammonium cloud level (P
about 0.5 bar) can be monitored in the near-infrared continuum (1.25
microns) and the upper stratospheric haze can be mapped in the
spectral regions of strong methane absorption.
We plan to monitor the impact regions and the surrounding areas of the
Jovian disk using the imaging spectrometer IRSPEC at the 3.5-metre NTT
telescope of ESO between July 16 and 31, 1994. This instrument will
record infrared spectra in the 1 - 5 microns range with a spectral
resolving power of about 3000 and a pixel size of 2 arcsec.
These observations should allow us to monitor the various cloud levels
of the Jovian atmosphere and their short-term and long-term evolution
after the impacts. The variations of the temperature profile at the
impact location will be recorded. Some minor tropospheric gaseous
species (NH3, PH3, CO, H2O,...) of the Jovian atmosphere might be
carried to higher levels and become observable.
Programme 14
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STRATOSPHERIC PHENOMENA ON JUPITER AFTER THE IMPACTS
3.6-metre telescope with the Far-Infrared instrument TIMMI
July 16 - 28, 1994
July 30 - 31, 1994
Tim A. Livengood (PI), Ted Kostyuk and P.N. Romani(NASA Goddard Space
Flight Center, Greenbelt, U.S.A.), C.F. Chyba (National Research
Council, Washington, U.S.A.), Hans Ulrich Kaeufl and Guenter Wiedemann
(ESO)
Stratospheric phenomena on Jupiter will be observed from the ESO
3.6-metre telescope, using the TIMMI thermal-infrared camera which
will also be used at the same time to study possible seismic
phenomena.
TIMMI is able to detect emission from warm gases in Jupiter's
uppermost atmosphere, the stratosphere, and has already been used to
study auroral emissions from Jupiter's poles. Preliminary
observations were conducted in March 1994. Observations of the impact
events will be sensitive to gases that are unique to Jupiter's deep
atmosphere that the impacts may eject upwards into the stratosphere.
We plan to study the alterations in Jupiter's stratospheric
composition and temperature profile and the rate at which the modified
atmosphere returns to its normal state. We may also be able to track
the drift of impact sites in the atmosphere in order to measure
large-scale stratospheric wind speeds, similar to tracking the
dispersal of gases thrown out by a volcano on Earth. Dust in
Jupiter's magnetosphere may affect the power delivered to the aurorae,
which may produce a detectable change in auroral brightness.
TIMMI observations of the impacts will give us information about two
regions of the Jovian system that are normally difficult to study, the
stratosphere and magnetosphere. A good understanding of these regions
is very important in preparing for planetary spacecraft missions and
in understanding the physics of atmospheric processes.
Programme 15
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SEISMIC WAVES AFTER THE IMPACTS
ESO 3.6-metre telescope with the Far-Infrared TIMMI instrument
July 16 - 28, 1994
July 30 - 31, 1994
Benoit Mosser (Institut d'Astrophysique, Paris, France;
PI). F. Billebaud (Observatoire de Lyon, France), P.O. Lagage and
M. Sauvage (Sap), France), P. Drossart and D. Gautier (DESPA, Meudon,
France), Phillipe Lognonne (IPG, Paris, France)
We shall use the TIMMI camera to monitor the seismic waves excited by
the impact, which will allow us to probe the interior of Jupiter. The
impacts will produce local shocks which will create various waves that
propagate through the planetary interior, very much like seismic waves
from earthquakes do through the Earth.
High-frequency waves, or transient waves (also known as primary
waves), will cross the entire planet in less than 2 hours. We hope to
detect their arrival times by means of the thermal perturbations they
induce when they arrive back in the upper troposphere and dissipate
their energy there. Low-frequency waves will be trapped in the
planetary interior and contribute to various modes of global
oscillations. In the days following the impacts, such modes will be
detectable through the thermal fluctuations associated with these
waves.
The monitoring of the front wave of the high frequency waves will be
conducted during the two hours following each impact, and will provide
us with a measurement of the sound speed profile in the fluid
envelope. The long-period modes will be continuously observed during
at least four observing "nights" (at these infrared wavelengths we can
also observe in the afternoon, before the Sun sets) after the
impacts. They will probe the planetary core and the region of the
envelope where hydrogen is in a fluid metallic phase.
These seismological observations may provide the first measurement of
the density profile in the interior, and will permit to discriminate
between the currently rather poorly constrained models of the interior
of Jupiter. We shall be able to test the state of hydrogen and helium
at pressures up to one megabar, and also how the giant planets were
formed.
The observation of the long period modes at ESO will be coordinated
with other observations conducted with similar cameras at the
Canadian-French Hawaii Telescope at Mauna Kea and at the Nordic
Optical Telescope at La Palma (Canarian Islands). This multi-site
project will permit us to obtain a good resolution of the various
seismological frequencies.
Programme 16
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IMAGING OF THE IO PLASMA TORUS AND JUPITER'S RING
1.54-metre Danish telescope with Special CCD Camera
July 17 - 24, 1994
Nicolas Thomas (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau,
Germany; PI)
The volcanically active, inner moon Io is the major source of heavy
ions (electrically charged atoms and molecules) in Jupiter's
magnetosphere. Approximately 1 ton/sec of mostly sulphur and oxygen
atoms is removed continuously from the satellite and become ionized in
Jupiter's magnetosphere where they form a torus of heavy ions
encircling Jupiter near Io's orbit, known as the Io Plasma Torus, or
the IPT). This torus has been studied by spacecraft and from the
ground since the mid-1970s, but the detailed mechanisms remain
obscure. It also seems that there must be an additional energy source
whose nature still remains unknown.
Comet Shoemaker-Levy 9's break-up in Jupiter's magnetosphere was first
thought to introduce a large enough mass to have an extreme effect on
the IPT. However, it is now apparent that the mass loss from the
comet will be too small by at least a factor of 1000 to affect the IPT
by increasing its mass. On the other hand, the comet may affect the
unknown energy source which maintains the stability of the emissions.
We will observe the IPT by imaging the ionized sulphur emissions at
visible and near-infrared wavelengths through narrow-band interference
filters, allowing to measure the electron temperature and density of
the IPT. These observations permit a rapid assessment of the IPT
during the comet encounter and would give the strongest indication
from ground-based observations of variability due to cometary
material.
The Jovian ring was discovered by the Voyager 1 spacecraft in 1979. It
was subsequently imaged from the ground on at least two occasions
around 1980 at visible wavelengths. Observations are very difficult
due to the ring's proximity to Jupiter (0.8 Jovian radii from
Jupiter's surface) and are best performed in the IR at wavelengths
near 2.2 microns. However, visible observations provide a higher
spatial resolution and are also of interest.
A large quantity of smaller dust particles is present around the comet
fragments. Although significant amounts of this material will miss
Jupiter entirely, it will intersect the ring plane and impact the
satellites near the ring. This could produce significant enhancements
in the mass of material in the ring. We will observe the ring in an
attempt to detect of perturbations in the ring due to the cometary
dust.
These observations will rely on the anti-blooming CCD system of the
Observatoire de Paris (see also Programme 7).
Programme 17
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RADIO OBSERVATIONS OF THE EFFECTS OF THE IMPACTS
15-metre Swedish-ESO Submillimetre Telescope with radio receivers
July 18 - 23, 1994
Daniel Gautier (PI), Danielle Bockelee-Morvan and Pierre Colom
(Observatoire de Paris-Meudon, France), D. Despois (Observatoire de
Bordeaux, France), Jacques Crovisier, Therese Encrenaz, E. Lellouch
and A. Marten (Observatoire de Paris-Meudon, France), Tobias Owen
(University of Hawaii, U.S.A.), D. Strobel (John Hopkins University,
U.S.A.)
The infalling fragments of comet Shoemaker-Levy 9 will evaporate in
the upper atmosphere of Jupiter. The various elements contained in
these fragments will then appear in gaseous form in the Jovian
atmosphere, and will form new molecules different from those
previously observed on the planet. If the fragments penetrate into the
deep atmosphere before they detonate, they may also lift molecules
which are formed in the interior of Jupiter and which have not yet
been detected up to high altitudes where they may then become
observable.
We have then two objectives, both based on a the possible modification
of the atmosphere of Jupiter following the impacts. First, to
determine the composition of the comet and secondly, to improve our
knowledge of the composition of the planet.
Observations by means of a radiotelescope of the radiation emitted by
Jupiter is a very powerful tool for detecting gaseous species. The
great sensitivity of the methods used in radioastromy will permit us
to detect the specific emissions of molecules, even if they only are
present in a very small numbers.
This is reason why we shall use the 15-metre SEST radiotelescope to
observe Jupiter immediately after the first impact and during the
following days. In this respect, the SEST has a unique advantage when
compared to other radiotelescopes in the world. Since Jupiter is
presently situated south of the celestial equator, we will be able to
perform much longer series of observations and at higher elevations
above the horizon than other radiotelescopes which are all located in
the Northen hemisphere. However, close coordination with groups
working at other sites has been organized.
5.4 The ST/ECF and observations with the Hubble Space Telescope
The Space Telescope European Coordinating Facility (ST/ECF) was
established in 1984 by the European Space Agency (ESA) in conjunction
with the European Southern Observatory (ESO). It is a group of
astronomers and computer scientists with the goal of helping European
astronomers make best use of the Hubble Space Telescope (HST). This is
achieved by providing specialist information and advice, developing
computer software for processing data from the telescope and
establishing and operating a full copy of the HST data archive.
The HST is 2.4-metre aperture telescope in low earth orbit designed as
a general purpose astronomical observatory for imaging and
spectroscopy in the ultra-violet, optical and near infrared regions of
the spectrum. It is a collaboration between NASA and the European
Space Agency and European astronomers are guaranteed to receive at
least 15% of the observing time for the duration of the ESA/NASA
agreement (currently ten years after HST launch).
HST was launched in 1990 by the Space Shuttle. Soon afterwards it was
discovered that the primary mirror of the telescope had the wrong
shape and that the performance was poorer than expected. The ST-ECF
was active in helping to produce computer software which allowed a
partial correction for this error. In late 1993 a repair mission of
the Space Shuttle very successfully installed corrective optics in the
telescope and the performance is now in most respects as good as the
original specification.
The Hubble Space Telescope will be among the most important of the
telescopes which will study the collision of comet Shoemaker-Levy 9
with Jupiter. Its position in orbit around the Earth allows very high
resolution images to be made both of the comet itself and the effects
on Jupiter after the collision.
Observations of the comet before impact will allow the orbits of the
fragments and their sizes to be better determined and hence allow
improvements of the estimates for the times of impact and likely size
of the subsequent explosions. Images already obtained have shown that
some of the fragments which appeared single from the ground are
actually double or multiple. The actual impacts will not be observable
with HST any more than from ground-based telescopes although a major
fireball may be seen rising above the edge of the planet's disc.
After the collision the effects on the atmosphere, rings, satellites
and environment of Jupiter will be studied over an extended period
using the HST. Six science programs will be executed and they will use
all four of HST's science instruments, two spectrographs and two
cameras.
6. ESOs Services to the Media
There are many signs that the upcoming collision between comet
Shoemaker-Levy 9 and giant planet Jupiter has caught the imagination
of the public. Numerous reports in the various media during the past
weeks and months describe the effects expected during this event.
In view of the unique nature of this event and the associated
astronomical observations, ESO has decided to provide special services
to the media. In particular, it is the intention to ensure that the
media will be able to follow the developments at La Silla closely and
in near-real time, and at the same time will be kept informed about
the observational results at other observatories all over the world.
This service will be available from the ESO Headquarters in Garching
near Munich, Germany, but special arrangements will also be made for
the media in Chile. In view of the complex and critical nature of
these observations, it will not be possible to arrange direct access
to the La Silla observatory during the observing period.
ESO will obtain all new information directly from the observers at La
Silla via the permanent satellite link to the ESO Headquarters in
Garching (Germany). For this, ESO is setting up the necessary internal
communication lines at La Silla which will allow this transfer to be
done at the shortest possible notice. While the observers cannot be
disturbed during the actual observations, they will communicate their
results and observational progress at regular intervals, and very
quickly, if and when "dramatic" events are observed.
ESO furthermore has complete and permanent access to the world-wide
communication net between all observers of this event, especially set
up for this purpose. The information available from this source will
first of all serve to alert the observers about the results in other
places and to warn them about new and unexpected developments.
Moreover, the Space Telescope European Coordinating Facility, the
ESA/ESO group that is responsible for the Hubble Space Telescope use
by European astronomers and which is housed at the ESO Headquarters,
will contribute with information regarding the observations with this
major observational facility.
With these important sources of information at its disposal, ESO is
therefore in a prime position to inform about and comment on the
latest developments at the shortest possible notice.
6.2 Specific arrangements
In practical terms, ESO's services to the media will be provided in
several steps.
The present Information Package marks the beginning of the "hot"
phase, during which the final preparations for the observations are
made.
Beginning on July 10, ESO will issue short daily bulletins with the
latest predictions and other news, related to these preparations of
observations at La Silla and elsewhere in the world. They can be
accessed via the ESO WWW Portal and they will be sent by fax to those
who request this service (see the addresses below).
The main event will be a Press Conference at the ESO Headquarters in
Garching which will commence on Saturday 16 July, 1994, at 20:00
(CEST). This will be just before the first impact is expected to
happen and will provide an excellent opportunity to inform the media
about the very latest developments.
The conference will begin with an in-depth briefing, followed by voice
contact to South Africa, from where we shall learn about the
observations of the first impact, which will be well visible from
there. The preparations at La Silla will be described by some of the
observers there (image telephone), and we will hear from the Space
Telescope Science Institute in Baltimore about the observations with
that telescope.
We expect that some of the media representatives will opt to pass the
night at the ESO Headquarters and to follow the first observations at
La Silla at distance (food and beverages will be provided).
Unexpected and "spectacular" events, should they happen, will be
announced and commented as quickly as possible. We will also contact
the La Silla observers immediately after the end of their observations
(in the early morning hours at Garching) and request live commentaries
about the initial results. At the same time, the latest images will be
transferred and made available.
There will be Press Conferences each day at 11:00 (CEST) on 17 - 22
July 1994, summarizing the previous night's results. Selected images
obtained at ESO the night before will be available on these occasions.
In Chile, ESO will publish a Spanish version of this Information
Package as soon as possible. The same images that will be at disposal
to the press in Europe will also be sent to Chile and made available
there. There will be a major Press Conference at the ESO Office in
Vitacura in the morning of July 17, 1994, with a presentation by ESO
astronomers of the first results from the night before. It is expected
that further Press Conferences will be held during the following days;
these will be announced in due time.
6.3 Contact addresses
Media representatives, who are interested in participating in the
Press Conference in Garching in the evening of July 16 and who would
like to stay at ESO during the following night, must obtain a personal
invitation by contacting Mrs. E. V\"olk of the ESO Information
Service (Tel.: +4989-32006276; Fax: +4989-3202362), before noon on
Wednesday, July 13, 1994. Otherwise access to the ESO Headquarters
cannot be guaranteed.
Participation in the activities in Chile should be arranged by
contacting the ESO Office in Santiago, Alonso de Cordova 3107,
Vitacura (Tel.: 228-5006).
6.4 Computer access to information from ESO
The World-Wide Web is a high-level tool for accessing information and
navigating between sites on the Internet. It is publicly available,
and has become very widely used in the last one or two years. To
access it, a "browser" is used. Examples are Mosaic (which can be
used on a computer system with good graphics capabilities) and Lynx
(which allows for line-mode access).
ESO's address on the World-Wide Web is:
http://http.hq.eso.org/eso-homepage.html
Accessing this address gives access to various areas, one of which
relates to ESO's activities in regard to the SL9/Jupiter event. This
information is kept constantly up to date, and will continue to be so
during the entire period of the collision between comet and planet.
Information from ESO will also be available on CompuServe (GO SPACE,
and then access the Astronomy Forum).
6.4. List of Available Images (July 5, 1994)
- Recent picture of the fragments of comet Shoemaker-Levy 9, obtained
with the Danish 1.5-metre telescope at La Silla (ESO Press Photo
SL9J/94-01)
- Aerial view of the La Silla observatory (ESO Press Photo SL9J/94-02)
- ESO special instrument TIMMI which will used to observe the SL9
event (ESO Press Photo SL9J/94-03)
- The Munich Fast Photometer (mounted at the Wendelstein observatory),
another instrument which will used to observe the SL9 event
(ESO Press Photo SL9J/94-04)
- The ST/ECF group at ESO (ESO Press Photo SL9J/94-05)