Press Releases

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eso0510 — Press Release
Young and Exotic Stellar Zoo
22 March 2005: Super star clusters are groups of hundreds of thousands of very young stars packed into an unbelievably small volume. They represent the most extreme environments in which stars and planets can form. Until now, super star clusters were only known to exist very far away, mostly in pairs or groups of interacting galaxies. Now, however, a team of European astronomers [1] have used ESO's telescopes to uncover such a monster object within our own Galaxy, the Milky Way, almost, but not quite, in our own backyard! The newly found massive structure is hidden behind a large cloud of dust and gas and this is why it took so long to unveil its true nature. It is known as "Westerlund 1" and is a thousand times closer than any other super star cluster known so far. It is close enough that astronomers may now probe its structure in some detail. Westerlund 1 contains hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two-thousand times larger than the Sun (as large as the orbit of Saturn)! Indeed, if the Sun were located at the heart of this remarkable cluster, our sky would be full of hundreds of stars as bright as the full Moon. Westerlund 1 is a most unique natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Galaxy live and die. From their observations, the astronomers conclude that this extreme cluster most probably contains no less than 100,000 times the mass of the Sun, and all of its stars are located within a region less than 6 light-years across. Westerlund 1 thus appears to be the most massive compact young cluster yet identified in the Milky Way Galaxy.
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eso0509 — Press Release
A Tale of Two Populations
15 March 2005: On the basis of stellar spectra totalling more than 200 hours of effective exposure time with the 8.2-m VLT Kueyen telescope at Paranal (Chile), a team of astronomers [1] has made a surprising discovery about the stars in the giant southern globular cluster Omega Centauri. It has been known for some time that, contrary to other clusters of this type, this stellar cluster harbours two different populations of stars that still burn hydrogen in their centres. One population, accounting for one quarter of its stars, is bluer than the other. Using the FLAMES multi-object spectrograph that is particularly well suited to this kind of work, the astronomers found that the bluer stars contain more heavy elements than those of the redder population. This was exactly opposite to the expectation and they are led to the conclusion that the bluer stars have an overabundance of the light element helium of more than 50%. They are in fact the most helium rich stars ever found. But why is this so? The team suggests that this puzzle may be explained in the following way. First, a great burst of star formation took place during which all the stars of the red population were produced. As other normal stars, these stars transformed their hydrogen into helium by nuclear burning. Some of them, with masses of 10-12 times the mass of the Sun, soon thereafter exploded as supernovae, thereby enriching the interstellar medium in the globular cluster with helium. Next, the blue population stars formed from this helium-rich medium. This unexpected discovery provides important new insights into the way stars may form in larger stellar systems.
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eso0428 — Press Release
Is This Speck of Light an Exoplanet?
10 September 2004: Is this newly discovered feeble point of light the long-sought bona-fide image of an exoplanet? A research paper by an international team of astronomers [2] provides sound arguments in favour, but the definitive answer is now awaiting further observations. On several occasions during the past years, astronomical images revealed faint objects, seen near much brighter stars. Some of these have been thought to be those of orbiting exoplanets, but after further study, none of them could stand up to the real test. Some turned out to be faint stellar companions, others were entirely unrelated background stars. This one may well be different. In April of this year, the team of European and American astronomers detected a faint and very red point of light very near (at 0.8 arcsec angular distance) a brown-dwarf object, designated 2MASSWJ1207334-393254. Also known as "2M1207", this is a "failed star", i.e. a body too small for major nuclear fusion processes to have ignited in its interior and now producing energy by contraction. It is a member of the TW Hydrae stellar association located at a distance of about 230 light-years. The discovery was made with the adaptive-optics supported NACO facility [3] at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory (Chile). The feeble object is more than 100 times fainter than 2M1207 and its near-infrared spectrum was obtained with great efforts in June 2004 by NACO, at the technical limit of the powerful facility. This spectrum shows the signatures of water molecules and confirms that the object must be comparatively small and light. None of the available observations contradict that it may be an exoplanet in orbit around 2M1207. Taking into account the infrared colours and the spectral data, evolutionary model calculations point to a 5 jupiter-mass planet in orbit around 2M1207. Still, they do not yet allow a clear-cut decision about the real nature of this intriguing object. Thus, the astronomers refer to it as a "Giant Planet Candidate Companion (GPCC)" [4]. Observations will now be made to ascertain whether the motion in the sky of GPCC is compatible with that of a planet orbiting 2M1207. This should become evident within 1-2 years at the most.
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eso0426 — Press Release
SINFONI Opens with Upbeat Chords
24 August 2004: The European Southern Observatory, the Max-Planck-Institute for Extraterrestrial Physics (Garching, Germany) and the Nederlandse Onderzoekschool Voor Astronomie (Leiden, The Netherlands), and with them all European astronomers, are celebrating the successful accomplishment of "First Light" for the Adaptive Optics (AO) assisted SINFONI ("Spectrograph for INtegral Field Observation in the Near-Infrared") instrument, just installed on ESO's Very Large Telescope at the Paranal Observatory (Chile). This is the first facility of its type ever installed on an 8-m class telescope, now providing exceptional observing capabilities for the imaging and spectroscopic studies of very complex sky regions, e.g. stellar nurseries and black-hole environments, also in distant galaxies. Following smooth assembly at the 8.2-m VLT Yepun telescope of SINFONI's two parts, the Adaptive Optics Module that feeds the SPIFFI spectrograph, the "First Light" spectrum of a bright star was recorded with SINFONI in the early evening of July 9, 2004. The following thirteen nights served to evaluate the performance of the new instrument and to explore its capabilities by test observations on a selection of exciting astronomical targets. They included the Galactic Centre region, already imaged with the NACO AO-instrument on the same telescope. Unprecedented high-angular resolution spectra and images were obtained of stars in the immediate vicinity of the massive central black hole. During the night of July 15 - 16, SINFONI recorded a flare from this black hole in great detail. Other interesting objects observed during this period include galaxies with active nuclei (e.g., the Circinus Galaxy and NGC 7469), a merging galaxy system (NGC 6240) and a young starforming galaxy pair at redshift 2 (BX 404/405). These first results were greeted with enthusiasm by the team of astronomers and engineers [2] from the consortium of German and Dutch Institutes and ESO who have worked on the development of SINFONI for nearly 7 years. The work on SINFONI at Paranal included successful commissioning in June 2004 of the Adaptive Optics Module built by ESO, during which exceptional test images were obtained of the main-belt asteroid (22) Kalliope and its moon. Moreover, the ability was demonstrated to correct the atmospheric turbulence by means of even very faint "guide" objects (magnitude 17.5), crucial for the observation of astronomical objects in many parts of the sky. SPIFFI - SPectrometer for Infrared Faint Field Imaging - was developed at the Max Planck Institute for Extraterrestrische Physik (MPE) in Garching (Germany), in a collaboration with the Nederlandse Onderzoekschool Voor Astronomie (NOVA) in Leiden and the Netherlands Foundation for Research in Astronomy (ASTRON), and ESO.
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