Picture of the Week

11 February 2008: Taking advantage of the presence of light echoes, a team of astronomers have used an ESO telescope to measure, at the 1% precision level, the distance of a Cepheid — a class of variable stars that constitutes one of the first steps in the cosmic distance ladder. The determination of the distance to RS Pup, following the method of the American astronomer Robert Havlen, is based on the measurement of the phase difference between the variation of the star and the variation of isolated nebular features. Because the luminosity of the star changes in a very distinctive pattern, the presence of the nebula allows the astronomers to see light echoes and use them to measure the distance of the star. The light that travelled from the star to a dust grain and then to the telescope arrives a bit later than the light that comes directly from the star to ...

29 January 2008: Artist's impression of the disc of matter surrounding the young stellar object MWC 147 as inferred from observations made with ESO's Very Large Telescope Interferometer. Thanks to these observations, astronomers have probed the inner parts of the disc of material surrounding the MWC 147, witnessing how it gains its mass before becoming an adult. A slice has been cut to show the inner structure better. The disc extends out to 100 times the distance between the Earth and the Sun (100 Astronomical Units — 100 AU). It is inclined by about 50 degrees as seen from Earth. The dust in the outer disc emits mainly at mid-infrared wavelengths, while close to the star there is also strong near-infrared emission from very hot gas. This gas is transported towards the forming star, increasing its mass at a rate of 7 millionths of the mass of the Sun — or about 2 ...

21 January 2008: Colour-composite image of the triplet of galaxies, catalogued as NGC 7173 (top), 7174 (bottom right) and 7176 (bottom left), and located 106 million light-years away towards the constellation of Piscis Austrinus (the 'Southern Fish'). This triplet of galaxies makes up part of the Hickson Compact Group HCG 90. NGC 7173 and 7176 are elliptical galaxies, while NGC 7174 is a spiral galaxy with quite disturbed dust lanes and a long, twisted tail. This seems to indicate that the two lower galaxies - whose combined shape bears some resemblance to that of a sleeping baby - are currently interacting. Astronomers have suggested that the three galaxies will finally merge. The size of the image is about 5.3 arcminutes. The image is based on data obtained with the VLT FORS1 instrument on ESO's Very Large Telescope through three different filters, B, V, and R. The data were extracted from the ESO Science ...

14 January 2008: Robert's Quartet is a family of four very different galaxies, located at a distance of about 160 million light-years, close to the centre of the southern constellation of the Phoenix. Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered by John Herschel in the 1830s. NGC 87 (upper right) is an irregular galaxy similar to the satellites of our Milky Way, the Magellanic Clouds. NGC 88 (centre) is a spiral galaxy with an external diffuse envelope, most probably composed of gas. NGC 89 (lower middle) is another spiral galaxy with two large spiral arms. The largest member of the system, NGC 92 (left), is a spiral Sa galaxy with an unusual appearance. One of its arms, about 100,000 light-years long, has been distorted by interactions and contains a large quantity of dust.

7 January 2008: These bizarre snow and ice formations, called "penitentes", form in high-altitude regions such as the Chajnantor plain, close to where the ALMA array will be located. These are ice blades produced by the competition between sublimation and melting of the snow. At Chajnantor at the summer solstice, the Sun is close to the zenith at noon, and penitents are vertical. This image was taken in December 2005. This image is available as a mounted image in the ESOshop

24 December 2007: Using ESO's Very Large Telescope, an international team of astronomers has discovered a stunning rare case of a triple merger of galaxies. This system, which astronomers have dubbed 'The Bird' - although it also bears resemblance with a cosmic Tinker Bell - is composed of two massive spiral galaxies and a third irregular galaxy. In this image, a 30-min VLT/NACO K-band exposure has been combined with archive HST/ACS B and I-band images to produce a three-colour image of the 'Bird' interacting galaxy system. The NACO image has allowed astronomers to not only see the two previously known galaxies, but to identify a third, clearly separate component, an irregular, yet fairly massive galaxy that seems to form stars at a frantic rate.

17 December 2007: On 3 and 4 December 2007, the two ALMA antenna transporters, Otto and Lore, were being loaded onto a barge on the Neckar at Heilbronn harbour (Germany) to start their long journey to Chile. From there, they will travel to Antwerpen (Belgium) and then put onto a ship towards the port of Mejillones, in the north of Chile, to finally reach the ALMA base, close to San Pedro de Atacama. The ALMA antenna transporters are each 20 metre long, 10 metre wide and 6 metre high, and weigh 130 tonnes. They will be able to transport a 115-tonne antenna and set it down on a concrete pad within millimetres of a prescribed position. Image taken in December 2007.

10 December 2007: The first three Japanese ALMA antennas of the Atacama Compact Array (ACA) at the ALMA Operation Support Facility, located close to the town of San Pedro de Atacama in the Chilean Atacama Desert, at an altitude of 2900m. At the time of the picture, in November 2007, the antennas were undergoing final tests before being handed over to the ALMA Observatory. The 12-m antennas were built by MELCO for the National Astronomical Observatory of Japan, one of the partners in the ALMA partnership.

1 December 2007: On 17 and 18 November 2007, the Regional Minister for Research of the Belgian French-speaking Community, Marie-Dominique Simonet, visited Paranal. This was part of a week-long visit to Brazil and Chile, in which the Minister promoted the 'Competitivity Poles' as well as Research and Education in this part of the world. The Minister was accompanied by a delegation comprising Claude Gonfroy and Jean-Luc Horward, members of her Cabinet, Jean-Pierre Swings, former member of the ESO Council, Claude Jamar from the Centre Spatial de Liėge, and Bill Collins, from the AMOS company which built the four Auxiliary Telescopes. Ten French-speaking Belgian journalists, including two TV crews, also joined the Minister for a day at Paranal. Felix Mirabel, ESO's Representative in Chile, Olivier Hainaut, Head of Science Operations at Paranal, and Ueli Weilenmann, were the hosts of the Minister. The Minister visited the telescopes and facilities on site and showed a clear ...

23 November 2007: Twice per year, the sunset passes exactly behind Paranal for somebody located on the summit of Armazones mountain, 20 kilometres away. The dates and time when this happens were calculated using coordinates of both sites found on Google Earth and taking into account atmospheric effects. The picture clearly shows 3 of the 4 big 8.2-m Unit Telescope (UT) domes (the 4th one is behind the others) of ESO's Very Large Telescope, the VST enclosure on their right and the high meteorological post with the DIMM tower on the extreme right. On the left of the picture, the partially opened domes of the smaller 1.8-m Auxiliary Telescopes (AT) are also visible. The image was taken with a Takahashi FS128 refractor telescope, a Canon20Da camera and special Solar filters, by Stéphane Guisard (ESO). Please remember that looking at the Sun through an optical device (Camera, Telescope, Binoculars etc.) is VERY dangerous, and ...