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eso0226 — Science Release
Surfing a Black Hole
16 October 2002: An international team of astronomers [2], lead by researchers at the Max-Planck Institute for Extraterrestrial Physics (MPE) , has directly observed an otherwise normal star orbiting the supermassive black hole at the center of the Milky Way Galaxy. Ten years of painstaking measurements have been crowned by a series of unique images obtained by the Adaptive Optics (AO) NAOS-CONICA (NACO) instrument [3] on the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory. It turns out that earlier this year the star approached the central Black Hole to within 17 light-hours - only three times the distance between the Sun and planet Pluto - while travelling at no less than 5000 km/sec. Previous measurements of the velocities of stars near the center of the Milky Way and variable X-ray emission from this area have provided the strongest evidence so far of the existence of a central Black Hole in our home galaxy and, implicitly, that the dark mass concentrations seen in many nuclei of other galaxies probably are also supermassive black holes. However, it has not yet been possible to exclude several alternative configurations. In a break-through paper appearing in the research journal Nature on October 17th, 2002, the present team reports their exciting results, including high-resolution images that allow tracing two-thirds of the orbit of a star designated "S2" . It is currently the closest observable star to the compact radio source and massive black hole candidate "SgrA*" ("Sagittarius A") at the very center of the Milky Way. The orbital period is just over 15 years. The new measurements exclude with high confidence that the central dark mass consists of a cluster of unusual stars or elementary particles, and leave little doubt of the presence of a supermassive black hole at the centre of the galaxy in which we live.
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eso0225 — Organisation Release
Four Eyes Are Better
26 September 2002: During the nights of September 15/16 and 16/17, 2002, preliminary tests were successfully carried out during which the light beams from all four VLT 8.2-m Unit Telescopes (UTs) at the ESO Paranal Observatory were successively combined, two by two, to produce interferometric fringes . This marks a next important step towards the full implementation of the VLT Interferometer (VLTI) that will ultimately provide European astronomers with unequalled opportunities for exciting front-line research projects. It is no simple matter to ensure that the quartet of ANTU, KUEYEN, MELIPAL and YEPUN , each a massive giant with a suite of computer-controlled active mirrors, can work together by sending beams of light towards a common focal point via a complex system of compensating optics. Yet, in the span of only two nights, the four VLT telescopes were successfully "paired" to do exactly this, yielding a first tantalizing glimpse of the future possibilities with this new science machine. While there is still a long way ahead to the routine production of extremely sharp, interferometric images, the present test observations have allowed to demonstrate directly the 2D-resolution capacity of the VLTI by means of multiple measurements of a distant star. Much valuable experience was gained during those two nights and the ESO engineers and scientists are optimistic that the extensive test observations with the numerous components of the VLTI will continue to progress rapidly. Five intense, technical test periods are scheduled during the next six months; some of these with the Mid-Infrared interferometric instrument for the VLTI (MIDI) which will soon be installed at Paranal. Later in 2003, the first of the four moveable VLTI 1.8-m Auxiliary Telescopes (ATs) will be put in place on the top of the mountain; together they will permit regular interferometric observations, also without having to use the large UTs.
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eso0209 — Science Release
VIMOS - a Cosmology Machine for the VLT
13 March 2002: One of the most fundamental tasks of modern astrophysics is the study of the evolution of the Universe . This is a daunting undertaking that requires extensive observations of large samples of objects in order to produce reasonably detailed maps of the distribution of galaxies in the Universe and to perform statistical analysis. Much effort is now being put into mapping the relatively nearby space and thereby to learn how the Universe looks today . But to study its evolution, we must compare this with how it looked when it still was young . This is possible, because astronomers can "look back in time" by studying remote objects - the larger their distance, the longer the light we now observe has been underway to us, and the longer is thus the corresponding "look-back time." This may sound easy, but it is not. Very distant objects are very dim and can only be observed with large telescopes. Looking at one object at a time would make such a study extremely time-consuming and, in practical terms, impossible. To do it anyhow, we need the largest possible telescope with a highly specialised, exceedingly sensitive instrument that is able to observe a very large number of (faint) objects in the remote universe simultaneously. The VLT VIsible Multi-Object Spectrograph (VIMOS) is such an instrument. It can obtain many hundreds of spectra of individual galaxies in the shortest possible time; in fact, in one special observing mode, up to 6400 spectra of the galaxies in a remote cluster during a single exposure, augmenting the data gathering power of the telescope by the same proportion. This marvellous science machine has just been installed at the 8.2-m MELIPAL telescope, the third unit of the Very Large Telescope (VLT) at the ESO Paranal Observatory. A main task will be to carry out 3-dimensional mapping of the distant Universe from which we can learn its large-scale structure. "First light" was achieved on February 26, 2002, and a first series of test observations has successfully demonstrated the huge potential of this amazing facility. Much work on VIMOS is still ahead during the coming months in order to put into full operation and fine-tune the most efficient "galaxy cruncher" in the world. VIMOS is the outcome of a fruitful collaboration between ESO and several research institutes in France and Italy, under the responsibility of the Laboratoire d'Astrophysique de Marseille (CNRS, France). The other partners in the "VIRMOS Consortium" are the Laboratoire d'Astrophysique de Toulouse, Observatoire Midi-Pyrénées, and Observatoire de Haute-Provence in France, and Istituto di Radioastronomia (Bologna), Istituto di Fisica Cosmica e Tecnologie Relative (Milano), Osservatorio Astronomico di Bologna, Osservatorio Astronomico di Brera (Milano) and Osservatorio Astronomico di Capodimonte (Naples) in Italy.
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