From our vantage point on Earth, comet 67P/CG has only just reappeared from behind the Sun. On 28 February 2014 ESO's Very Large Telescope (VLT) directed its gaze towards the comet as soon as it became visible from ESO's Paranal Observatory in Chile. ESO is collaborating with ESA to monitor the comet from the ground as it is approached by Rosetta over the coming months. These observations will prepare for the spacecraft's major rendezvous with the comet, planned for August of this year (see potw1403a).
This new image, and many more to come, will be used by ESA to refine Rosetta's navigation, and to monitor how much dust the comet is releasing. The image on the left was created by stacking the individual exposures to show the background stars — they were then shifted to compensate for the motion of the comet, which appears as a small dot right on top of one of the star trails (at the centre of the circle). The image on the right shows the comet with the stars subtracted out.
This new image shows a brightening of the comet, indicating that the ice at its heart has started to evaporate as it warms up in its approach to the Sun. Just like the Rosetta spacecraft, the comet itself is emerging from hibernation.
High on the Chajnantor Plateau in the Chilean Andes lies the Atacama Large Millimeter/submillimeter Array (ALMA), an observatory surrounded by large expanses of dry landscape. Perhaps surprisingly, the region is home to a number of different wildlife species, many of which occasionally pop up near to the observatory. Further south, ESO’s La Silla Observatory recently had visits from a South American grey fox (potw1406a), and wild horses (potw1344a).
The most recent cute visitor to ALMA is this vicuña fawn, found on 16 February 2014 by ALMA workers. The fawn was only a few weeks old, weakened after it was chased by foxes until it lost sight of its herd.
After a couple of unsuccessful attempts the following day to return the fawn to its herd, the workers transferred it to the Wildlife Rescue and Rehabilitation Center at the Universidad de Antofagasta, where it is being treated so that it can eventually be released on the Andean plateau approximately one year from now.
Bereft of colour in this striking infrared image, the sweeping curves of ESO's Headquarters clash with the frosty natural beauty of the surrounding trees. The extreme curvature visible in this image is due to the photographer's use of a fisheye lens, which distorts the view and causes the building to encircle the pale foliage and frame the sky above. The foliage appears to be bright as it reflects the infrared light, and the pale white hue comes from the photographer applying a white colour balance to the tree leaves.
The precise curves of concrete, glass, and steel give clues as to the Headquarters building's peculiar structure. In 1981 an article in ESO's The Messenger described the ESO building as "a labyrinth of the kind used to test the intelligence of rats". But, fortunately for ESO, the writer soon noted that "human beings are on average cleverer than rats, and the problem is quickly solved".
This image was taken by ESO computer specialist Dirk Essl.
Launched on the morning of Thursday, 19 December 2013, the satellite is on a quest to build a 3D map of our galaxy over the next five years. Mapping the sky has been one of humanity's quests since the dawn of time, and Gaia will take our understanding of our stellar neighbourhood to a whole new level. It will measure very precisely the positions and motions of about one billion stars in our galaxy, to explore the Milky Way's composition, formation and evolution.
These new observations are the result of a close collaboration between ESA and ESO to monitor the spacecraft from the ground. Gaia is the most accurate astrometric device ever built, but in order for its observations to be useful it needs to know exactly where it is in the Universe. The only way to know the velocity and position of the spacecraft with very high precision is to observe it on a daily basis from the ground — using telescopes including ESO's VST in a campaign known as Ground-Based Optical Tracking, or GBOT.
The VST is a state-of-the-art 2.6-metre telescope equipped with OmegaCAM, a monster 268-megapixel CCD camera with a field of view four times the area of the full Moon. The VST captured these images using OmegaCAM on 23 January 2014, taken about 6.5 minutes apart. Gaia is clearly visible as a small spot moving against a background of stars. Its location is circled in red. In these images, the spacecraft is about a million times fainter than is detectable by the naked eye.
Gaia was previously observed in December 2013 by the VST, very soon after its launch — it is one of the closest objects ever observed by the VST. It appeared in precisely the location expected, highlighting a successful collaboration between ground- and space-based astronomy!
Perched precariously on the edge of the habitable world, life manages to cling on. On the outskirts of the hot, dry Atacama Desert, this hardy South American grey fox has just awoken, stretching leisurely. These foxes are generally active during the night, making the most of the drop in temperature that comes with a respite from the hot Chilean Sun.
In the background there are other signs of life. This white dome houses the Swiss 1.2-metre Leonhard Euler Telescope, which is protected from the harsh conditions by its outer shell. As the skies grow darker at ESO’s La Silla Observatory another famously nocturnal species, the astronomer, wakes up, stretches, and gets ready to scan the skies with buzzing and whirring technology.
This image was taken by ESO Photo Ambassador Malte Tewes and submitted to the Your ESO Pictures Flickr group. The Flickr group is regularly reviewed and the best photos are selected to be featured in our popular Picture of the Week series, or in our gallery.
This beautiful panorama of ESO's Paranal Observatory was taken on 5 July 2012, and marks one of the driest days ever recorded at the Very Large Telescope complex. Paranal sits like an island in the middle of the frame, with massive cloud banks floating below, over the distant Pacific Ocean.
The extremely low humidity at Paranal during this period was recorded by a water vapour radiometer known as LHATPRO, which monitors the atmosphere to support the observations carried out at the observatory . Meteorologists from two Chilean universities identified the cause for these unusually dry conditions: high-altitude Antarctic air moving far to the north, and descending over Paranal.
This cold front lingered around Paranal for over 12 hours, causing a record-low level of humidity in the air above the observatory . Florian Kerber (ESO) and colleagues analysed this unusual weather, publishing the results in a paper in the Monthly Notices of the Royal Astronomical Society on 29 January 2014, available here.
So, a dry desert… what is so special about that? Well, dryness of this magnitude is normally experienced at much higher altitudes, for example at the ALMA Observatory on the Chajnantor Plateau, which is located at 5000 metres above sea level — at 2635 metres, the altitude of Paranal is around half of this. Given that infrared observations can be best taken when there is little water vapour in the air, this could mean that routine monitoring using the LHATPRO radiometer will give astronomers the opportunity to exploit future dry spells at Paranal, to obtain great infrared observations of the Universe around us.
The photo was taken by ESO photo ambassador Gabriel Brammer, who coincidentally experienced the sunset that immediately preceded this dry spell, and found it to be extraordinarily clear and beautiful. Gabriel works as an astronomer at the ESO La Silla-Paranal Observatory. When not supporting the operations of the observatory, he studies the formation and evolution of distant galaxies using the most sophisticated telescopes and instrumentation in the world, including the ESO Very Large Telescope and the Hubble Space Telescope.
 The Low Humidity and Temperature Profiling radiometer (LHATPRO), manufactured by Radiometer Physics GmbH in Germany, uses strong spectral lines from certain elements to measure the water content of the atmosphere.
 The humidity is measured in the form of precipitable water vapour — a measure of atmospheric water content. It is the amount of water in a column of the atmosphere if it were all to fall as rain. In this case only 0.1 mm of precipitable water vapour was measured — much less than the usual (but already low) figure of 2 mm at Paranal.
Astronomers do not always swim at the swimming pool at the Paranal Observatory Residencia, but when they do, they like to show how physical principles work. In this picture the French ESO astronomer Jean-Baptiste Le Bouquin is demonstrating how waves — not light waves, but water waves — can combine, or interfere, to create larger waves.
The combination of light waves is the main principle behind the VLT Interferometer: the light waves captured by each one of the four 8-metre telescopes are combined using a network of channels and mirrors. This way the spatial resolution of the telescope is vastly increased and, with enough exposure time, the cameras and instruments can reveal the same level of detail as a telescope with a 130-metre diameter mirror could, far bigger than any telescope in existence.
This image was taken by award-winning editorial and commercial photographer Max Alexander. See also Tribute to ESO’s Unsung Heroes, a video released by ESO for its 50th anniversary in 2012. The video is composed of a set of images, most of which were taken by Alexander, who was visiting the ESO sites for a project dedicated to ESO’s anniversary.
ESA's Rosetta spacecraft will wake up today, 20 January, after 31 months in deep space hibernation, to finally close in on comet 67P/Churyumov-Gerasimenko (67P/CG).
This image shows the most recent observations of the 4-kilometre diameter comet, taken on 5 October 2013 by ESO's Very Large Telescope (VLT) when the comet was around 500 million kilometres away — before it passed behind the Sun and out of view from Earth's perspective.
For this image, a long series of observations was processed to reveal both the comet without the background stars (on the left panel), and the star field with the track of the comet marked (on the right). Viewed against a crowded star field towards the centre of the Milky Way, the comet was still so far from the Sun that the icy nucleus was not releasing any gas or dust, and appears as a simple spot. As it approaches the Sun, its surface will heat up and its ices will sublimate, dragging dust out to form a tail.
The observation marks the start of a close collaboration between ESA and ESO to monitor the comet from the ground during Rosetta's encounter with 67P/CG later this year. Rosetta was launched in 2004 and aims to explore the surface of the comet, deploying a lander down onto 67P/CG to see what its surface is like .
The comet is on a 6.5-year orbit around the Sun and is currently out towards the orbit of Jupiter. It will be closest to the Sun — roughly between the orbits of Earth and Mars — in August 2015. This image suggests that the comet is not yet active, so scientists will be keen to check in on the comet again in February, when it is next observable by the VLT, and much closer to the Sun.
In the meantime, the observations carried out in October have been used to confirm the comet's orbit ahead of the major rendezvous manoeuvre planned for Rosetta in May, to line it up for orbiting 67P/CG in August. Further calculations will be made once Rosetta sights the comet in its own imaging system.
 Since its launch, Rosetta has travelled around the Sun five times, picking up speed and aligning itself with its final destination. For the coldest leg of the mission, as Rosetta ventured out beyond the orbit of Jupiter, the spacecraft was put into deep-space hibernation. 67P/CG is on a reasonably stable and well-known orbit, meaning that calculations for Rosetta's trajectory could be made far in advance of the spacecraft's launch, and it is far enough away from the Sun to make it a safe target.
- VLT snap of comet 67P/Churyumov-Gerasimenko in October 2013
- The path of comet 67P/Churyumov-Gerasimenko in October 2013
- ESA Space Science Image of the Week
- ESA information on Rosetta
- ESA Call for Media: Rosetta Wake Up Event
- ESO's Very Large Telescope
Thanks to ESO’s Photo Ambassadors we can enjoy sensational images taken at the ESO sites on the remote mountaintops of Chile. Babak Tafreshi has captured this fine panoramic view of the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) at twilight. Resembling a frame from a science fiction movie, the technological spectacle of ALMA against the raw natural power of the landscape on the Chajnantor Plateau, 5000 metres above sea level, results in fascinating images like this one.
There are a few details you shouldn't miss in this panoramic photo of ALMA (seen more clearly in the zoomable version), all lying between the two groups of antennas: the "Earth's shadow" and "Belt of Venus" phenomena, visible as the dark blue and light pink bands stretching across the sky, and the planet Jupiter, seen right above the mountain in the background.
ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
Gaze up at the night sky from ESO's Paranal Observatory in Chile, and you will be greeted with a stunning view like this one. Flecks of blue, orange, red; each a different star, galaxy, nebula, or more, together forming a sparkling sky overhead. Astronomers peer at this beautiful backdrop, trying to unravel the mysteries of the Universe.
To do this, they use telescopes like the ones shown here, the VLT Auxiliary Telescopes. This image shows three of the four moveable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: they reveal details that would be visible with a telescope as large as the distance between them.