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Tag Archives: ESO

From an ESO press release, October 26, 2016:

An international team of astronomers has discovered glowing gas clouds surrounding distant quasars, active galaxies less than two billion years after the Big Bang. This new survey by ESO’s Very Large Telescope indicates that halos around quasars are far more common than expected. The properties of the halos in this surprising find are also in striking disagreement with currently accepted theories of galaxy formation in the early Universe.

Bright halos around distant quasars

Credit: ESO/Borisova et al.

The study involved 19 quasars, selected from among the brightest that are observable with the telescope’s MUSE instrument. Previous studies have shown that around 10% of all quasars examined were surrounded by halos, made from gas known as the intergalactic medium. These halos extend up to 300,000 light-years away from the centers of the quasars. This new study, however, has thrown up a surprise, with the detection of large halos around all 19 quasars observed – far more than the two halos that were expected statistically.

The newly detected halos also revealed another surprise: they consist of relatively cold intergalactic gas – approximately 10,000 degrees Celsius. This revelation is in strong disagreement with currently accepted models of the structure and formation of galaxies, which suggest that gas in such close proximity to galaxies should have temperatures upwards of a million degrees.

Links: full ESO press release, including video animations.

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From an ESO press release, April 22, 2015:

Astronomers using the HARPS planet-hunting machine at ESO’s La Silla Observatory in Chile have made the first-ever spectroscopic detection of visible light reflected off an exoplanet. These observations also revealed new properties of this famous object, the first exoplanet ever discovered around a normal star: 51 Pegasi b. The result promises an exciting future for this technique, particularly with the advent of next generation instruments and future telescopes, such as the E-ELT.

The exoplanet 51 Pegasi b lies some 50 light-years from Earth in the constellation of Pegasus. It was discovered in 1995 and will forever be remembered as the first confirmed exoplanet to be found orbiting an ordinary star like the Sun. It is also regarded as the archetypal ‘hot Jupiter’ — a class of planets now known to be relatively commonplace, similar in size and mass to Jupiter, but which orbit much closer to their parent stars.

Credit: ESO/M. Kornmesser/Nick Risinger

Currently, the most widely used method to examine an exoplanet’s atmosphere is to observe the host star’s spectrum as it is filtered through the planet’s atmosphere during transit – a technique known as transmission spectroscopy. An alternative approach is to observe the system when the star passes in front of the planet, which primarily provides information about the exoplanet’s temperature.

The new technique does not depend on finding a planetary transit, and so can potentially be used to study many more exoplanets. It allows the planetary reflected light spectrum to be directly detected in visible light, which means that different characteristics of the planet that are inaccessible to other techniques can be inferred.

The host star’s spectrum is used as a template to guide a search for a similar signature of light that is expected to be reflected off the planet as it describes its orbit. This is an exceedingly difficult task as planets are incredibly dim in comparison to their dazzling parent stars. The signal from the planet is also easily swamped by other tiny effects and sources of noise. In the face of such adversity, the success of the technique when applied to the HARPS data collected on 51 Pegasi b provides an extremely valuable proof of concept.

Link: ESO press release

Scientists at the Max Planck Institute for Extraterrestrial Physics in Germany have produced the first detailed three-dimensional map of the stars that form the inner regions of our Milky Way, the nuclear bulge (see p. 389).

Credit: ESO/NASA/JPL-Caltech/M. Kornmesser/R. Hurt

Using publicly available data from ESO’s VISTA survey telescope in Chile, the team found a peanut-shaped bulge with an elongated bar and a prominent X-structure, which had been hinted at in previous studies. This indicates that the Milky Way was originally a pure disk of stars, which then formed a thin bar, before buckling into the boxy peanut shape seen today.

The scientists expect that this measurement of the three-dimensional density of the bulge will help to constrain galaxy evolution models for both our Milky Way and spiral galaxies in general. It will also support a number of further studies on different stellar populations, gas flows, or microlensing.

Read the MPE press release and the ESO press release for more images and a movie simulation of the bulge rotating. The research is published as “Mapping the three-dimensional density of the Galactic bulge with VVV red clump stars” by C. Wegg et al. in the Monthly Notices of the Royal Astronomical Society.

New observations from the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile have given astronomers the best view yet of how vigorous star formation can blast gas out of a galaxy and starve future generations of stars of the fuel they need to form and grow. Dramatic new images show enormous outflows of molecular gas ejected by star-forming regions in the nearby Sculptor Galaxy. These new results help to explain the strange paucity of very massive galaxies in the Universe. The study was published in the journal Nature on 25 July 2013.

The Sculptor Galaxy, also known as NGC 253, is a spiral galaxy located in the southern constellation of Sculptor. Lying at a distance of around 11.5 million light-years from our Solar System it is one of our closer intergalactic neighbors, and one of the closest ‘starburst galaxies,’ those which produce at an exceptionally high rate. Using ALMA, astronomers have discovered billowing columns of cold, dense gas fleeing from the center of the galactic disc. These results may help to explain why astronomers have found surprisingly few high-mass galaxies throughout the cosmos.

Credit: ALMA (ESO/NAOJ/NRAO)/Erik Rosolowsky

See the full ESO press release here, including links to more images and movies.

Recent observations from April this year of the galactic center have revealed that parts of the in-falling gas cloud, which was detected in 2011, have already swung past the black hole at the heart of our Milky Way. Due to the tidal force of the gravity monster, the gas cloud has become further stretched, with its front moving now already 500 km/s faster than its tail. This confirms earlier predictions that its orbital motion brings it is close to the black hole, that it will not survive the encounter. With the new, detailed, observations the astronomers from the Max Planck Institute for Extraterrestrial Physics (MPE) can now also place new constraints the origins of the gas cloud, making it increasingly unlikely that it contains a faint star inside, from which the cloud might have formed.

eso1151a

Credit: ESO/MPE/Marc Schartmann

The full article, with accompanying graphics, may be found here.