Communiqués de presse

2 août 1996: The past four centuries have seen dramatic improvements in astronomical equipment, in terms of better and larger telescopes, more accurate and sensitive detectors and, not the least, by advanced space instruments with access to new spectral regions. However, until recently there has been little progress on another equally important front, that of quantifying the unavoidable influence of this equipment on the astronomical data they produce. For a long time, astronomers have desired to remove efficiently these `instrumental effects' from their data, in order to give them a clearer understanding of the objects in the Universe and their properties. But it is only now that this fundamental problem can finally be tackled efficiently, with the advent of digital imaging techniques and powerful computers.

1 août 1996: The Local Group of Galaxies consists of a few large spiral galaxies - for instance the Milky Way galaxy in which we live, and the Andromeda galaxy that is visible to the unaided eye in the northern constellation of the same name - as well as two dozen much smaller galaxies of mostly irregular shape. Whereas the larger galaxies have extended halos of very old stars, no such halos have ever been seen around the smaller ones. Now, however, Dante Minniti and Albert Zijlstra [1], working at the ESO 3.5-metre New Technology Telescope (NTT), have found a large halo of old and metal-poor stars around one of the dwarf galaxies in the Local Group. This finding is quite unexpected. It revises our understanding of star formation in these galaxies and provides important information about the past evolution of galaxies [2].

25 juillet 1996: Each of the giant Zerodur mirrors for the four unit telescopes of the ESO Very Large Telescope (VLT) , with a diameter of 8.2-metres and a total area of more than 50 square metres, will be supported by a complex steel structure, referred to as the M1 Cell . This structure will also support the M3 Tower that protrudes from the central hole of the mirror and carries a flat mirror (M3) that serves to reflect the light towards the Nasmyth platforms on either side of the telescope. On these platforms are placed the heavy instruments that will record the light from celestial objects collected by the telescope.

25 juillet 1996: Using telescopes in Chile, Europe, Australia and the USA, an international team of astronomers [1] has discovered large empty regions ('holes') in what they refer to as the 'local Universe'. These regions, as well as others with excess mass density are revealed by a study of the motions in space of more than 2000 galaxies. They are among the largest structures ever seen in the Universe and have diameters of up to 100 million light years.

18 juin 1996: Astronomy On-Line is a major, all-European project that will take place in conjunction with the 4th European Week for Scientific and Technological Culture later this year. It is based on intensive use of the World-Wide-Web (WWW) and represents the first large-scale attempt in the world to bring together pupils and their teachers all over one continent to explore challenging scientific questions, using modern communication tools, both for obtaining and for communicating information.

30 mai 1996: The latest areal views showing the VLT building site at Cerro Paranal gives a good impression of the progress of the construction

24 mai 1996: The programme will be carried out in a collaboration between the European Association for Astronomy Education (EAAE) [1] and the European Southern Observatory, and together with the European Commission (EC).

20 mai 1996: Observations of Comet 1995 O1 (Hale-Bopp) continued at ESO during the period of May 10 - 14, 1996, with the MPI/ESO 2.2-m telescope and the multimode EFOSC II instrument. Both direct images and spectra were obtained.

20 mai 1996: The active phase of Astronomy On-Line will start on October 1 and reach a climax on November 18 - 22, 1996. A new and unknown comet was discovered by Robert Evans on a photographic plate, obtained by M. J. Drinkwater on May 10, 1996, with the UK Schmidt telescope at Siding Spring Australia. More observations were made within the next days and the comet was soon given the designation 'Comet 1996 J1' (i.e. the first comet to be found in the period May 1 - 15, 1996). Following astronomical tradition, it was also named after the discoverers.

18 avril 1996: On April 12, two observers in Australia and Japan independently reported the sudden appearance of a supernova in the southern elliptical galaxy NGC 5061, a prominent object in the Centaurus constellation (IAUC 6380). The magnitude was about 13 (visual) and the exact position was measured as R.A. = 13h 18m 01.13s, Decl. = -26d 50m 45.3s (equinox 2000.0), or about 52 arcsec west and 31 arcsec south of the galaxy's center.

22 mars 1996: A series of CCD frames, showing the inner coma of Comet Hale-Bopp, was obtained with the SUSI high angular resolution camera at the ESO 3.5-metre New Technology Telescope (NTT) under very good seeing conditions in the morning of March 20, 1996.

19 mars 1996: The most recent ESO observations of bright Comet Hyakutake have shown rapid changes in the innermost coma, within a few hundred kilometres from the cometary nucleus. This result has only become possible because of the unusual combination of a bright comet being near the Earth, together with the excellent imaging quality of the ESO 3.5-metre New Technology Telescope (NTT).

17 mars 1996: This new image obtained with ESO's New Technology Telescope (NTT) shows the circumnuclear region of the comet Hyakutake, expected to pass close to Earth in the upcoming days.

15 mars 1996: Following recent observations at the ESO La Silla Observatory, there is now no doubt that Comet Hyakutake - as hoped - is developing into a major object! In any case, the observed, very complex structure as well as the extent of the tail system is typical of a bright and beautiful comet.

13 mars 1996: A complete, optical spectrum of Comet Hyakutake was obtained with the ESO 1.52-m telescope (La Silla Observatory) by Hilmar Duerbeck (ESO) on UT March 8.3, 1996. For this observation, the Boller & Chivens spectrograph with a new UV-sensitive CCD chip was used. The subsequent data reduction was performed by the observer and Stefano Benetti (ESO) at ESO's office in Santiago de Chile.

7 mars 1996: A bright 'new' star was discovered by Japanese amateur astronomer Yukio Sakurai in late February 1996. It is located in the star-rich, southern constellation of Sagittarius (The Archer) and qualifies to join an extremely select class of stars. In fact, we know only one additional object of this type and the remains of two - possibly three - others. Compared to the 6000 stars in the sky seen with the naked eye, the several millions so far catalogued, and the billions of stars photographed, it is a very special class indeed. Nevertheless, Sakurai's star holds unique information about a dramatic evolutionary state, which all stars must to pass through whose masses are more than a few times that of the Sun, but still too small to produce a supernova explosion. This happens just before they end their active life and cool down into visual oblivion.

6 mars 1996: With the help of a new and more sensitive receiver, recently installed on the 15-metre Swedish-ESO Submillimetre Telescope (SEST) at the European Southern Observatory on the La Silla mountain in Chile, a team of European astronomers [1] has succeeded in discovering the first extra-galactic silicon-monoxide (SiO) maser . It is located in the atmosphere of the largest known star in the Large Magellanic Cloud, a satellite galaxy to the Milky Way. This observational feat now opens new, exciting possibilities for the study of individual stars in other galaxies in the Local Group. The continued search for extra-galactic SiO masers is a joint project of European and Australian astronomers, to be carried on with even more advanced instruments that will become available in the near future.

4 mars 1996: This is the most detailed image so far obtained of the complex tail system of Comet Hyakutake. It was obtained with the ESO 1-m Schmidt telescope at La Silla on February 28.36 UT under good observing conditions by ESO night assistant Oscar Pizarro. The exposure lasted 60 min and was made on sensitized Kodak Pan 4415 film behind a GG385 filtre. This emulsion/filtre combination allows to record a broad spectral interval (3900-7000 A) whereby faint structures are better seen. However, detailed spectral information, by which the emitters may be identified, is lost for the same reason.

4 mars 1996: Spectra of Comet Hyakutake were obtained at the ESO La Silla Observatory on February 29.3 UT by Klaus Simon (Institute for Astronomy and Astrophysics, University of Munich, Germany) and Chris Lidman (ESO-Chile). They used the Danish 1.54-m telescope with the multi-mode DFOSC instrument and a large CCD. The slit was centred on the brightest part of the cometary coma. The frames were reduced by S. Benetti (ESO-Chile).

2 mars 1996: These false-colour images are reproductions from a short-exposure CCD frame, obtained with the Danish 1.54-metre telescope and the DFOSC instrument with a 2052 x 2052 pix Loral/Lesser CCD. They show the innermost coma of Comet Hyakutake and the pronounced asymmetry of the dust distribution around the nucleus.