Monday, October 31, 2016

Galaxies Old and New Share a Common Thread

False-color image of SPT-CL J0546–5345 at z = 1:067. Gemini GeMS/GSAOI Ks (this work) = red, HST ACS F814W = green, HST ACS F606W = blue. The red polygon shows the approximate sky coverage of the GSAOI pointings. PSF stars are indicated by white circles. The star near the top of the image with two circles is a binary star. The inset at lower left is a zoom-in of the cluster core. The scale bars at lower right of the inset and full image show the angular and physical projected distances at the cluster redshift. The red, green and blue spots on the scale bar in the inset show the PSF FWHM for each band. N is up and E is left. Credit: Gemini Observatory/AURA. Full Resolution PNG


Summary: A team using the Gemini Multi-Conjugate Adaptive Optics System (GeMS) with the Gemini South Adaptive Optics Imager (GSAOI) have, for the first time, measured the stellar masses relative to the physical sizes of several galaxies in a cluster at a lookback time of about 5 billion years. The data suggest that the relationship between stellar mass and size has a constant slope over time. This leads to the conclusion that the most likely evolutionary course for the larger (more expansive) galaxies we see in the nearby Universe is either from the combination of smaller galaxies and/or outflows from black holes at galactic cores. 

During the past 20 years astronomers have developed a picture for the evolution of the size and structure of galaxies – from the formation of the first galaxies in the early Universe, to what we see today. One of the most important discoveries is that the most massive galaxies in the early Universe, at z > 1 (i.e. when the universe was about 5 billion years old), were much smaller in physical size (for their stellar mass, by a factor of between 2 to 6) when compared to galaxies we see in the local Universe today. 

It is still unclear what the main physical mechanism(s) is/are that allow this extraordinary growth in the size of these galaxies over time. Mergers of galaxies with similar stellar masses (major mergers), accretion of small satellite galaxies (minor mergers), or the rapid loss of mass caused by active galactic nuclei (AGN), or supernova winds (adiabatic expansion) could all potentially be responsible for the dramatic growth in the size of these galaxies. To distinguish between these proposed physical mechanisms, astronomers use the stellar mass – size relation (i.e. the relation between the mass of the galaxies measured from light of the stars and the intrinsic size of the galaxies represented by their effective radii). 

The accuracy in determining the stellar mass - size relation for a galaxy depends most strongly on the resolution of the images and the rest-frame wavelength (assuming no redshift due to the expansion of the Universe) of the observations. The resolution is required to measure accurately the sizes of the most compact galaxies. 

Using the most advanced adaptive optic system on the planet, the Gemini Multi-Conjugate Adaptive Optics System (GeMS), and the Gemini South Adaptive Optics Imager (GSAOI), an international team of astronomers, led by Sarah Sweet from the Australian National University in Canberra, Australia, have measured, for the first time, the stellar mass – size relation for several galaxies in a cluster environment (SPT-CL J0546−5345 at a redshift of z = 1.067), with an average resolution of 450 parsecs in radius at the cluster redshift, and at the rest-frame wavelength dominated by an old (redder) stellar population. The authors of this study find that the stellar mass - size relation at the redshift of the cluster (z ~ 1) is offset from that at z ~ 0. The result is consistent with previous findings, where the primary mechanism for galaxy growth in size is minor mergers. 

One of the most important results presented in this study is that the slope of the stellar mass – size relation plot of the massive galaxies at z ~ 1 is consistent with the slope seen for the galaxies with same stellar masses in the local Universe. This result suggests that the massive galaxies in the cluster SPT-CL J0546-5345 has ceased its early, rapid growth via major mergers, leaving the accretion of small satellite galaxies (minor mergers) and/or the rapid loss of mass caused by active galactic nuclei (AGN), as the principal mechanism to increase the size of the galaxies. 

This work is accepted for publication in Monthly Notices of the Royal Astronomical Society and a preprint is available here


Saturday, October 29, 2016

How planets like Jupiter form

Core accretion: A 10 Jupiter-mass planet is formed and is placed at 50 AU from the star. 
The planet has opened a gap in the circumstellar disk. 
Image: J. Szulagyi, JUPITER code

Gravitational instability simulation: Two snapshots in the early and late stage of the simulation at 780 years and 1942 years. 
The second snapshot shows only 4 clumps remaining among those initially formed. 
Image: Lucio Mayer & T. Quinn, ChaNGa code


Animation by J. Szulagyi, L. Mayer, T. Quinn and C. Gheller/ETH Zurich/University of Zurich/CSCS.


Young giant planets are born from gas and dust. Researchers of ETH Zürich and the Universities of Zürich and Bern simulated different scenarios relying on the computing power of the Swiss National Supercomputing Centre (CSCS) to find out how they exactly form and evolve. They compared their results with observations and were able to show amongst others a big difference between the postulated formation mechanisms.

Astronomers set up two theories explaining how gaseous giant planets like Jupiter or Saturn could be born. A bottom-up formation mechanism states that first, a solid core is aggregated of roughly ten times the size of the Earth. «Then, this core is massive enough to attract a significant amount of gas and keep it,» explains Judit Szulágyi, post-doctoral fellow at the ETH Zürich and member of the Swiss NCCR PlanetS. The second theory is a top-down formation scenario: Here the gaseous disk around the young star is so massive, that due to self-gravity of the gas-dust, spiral arms are forming with clumps inside. Then, these clumps collapse via their own gravity directly into a gaseous planet, similar to how stars form. The first mechanism is called «core-accretion», the second one «disk instability». In both cases, a disk forms around the gas-giants, called the circumplanetary disk, which will serve as a birth-nest for satellites to form.

To find out which mechanism actually takes place in the Universe, Judit Szulágyi and Lucio Mayer, Professor at the University of Zürich, simulated the scenarios on Piz Daint supercomputer at the Swiss National Supercomputing Centre (CSCS) in Lugano. «We pushed our simulations to the limits in terms of the complexity of the physics added to the models,» explains Judit Szulágyi: «And we achieved higher resolution than anybody before.» In their studies published in the «Monthly Notices of the Royal Astronomical Society» the researchers found a big difference between the two formation mechanisms: In the disk instability scenario the gas in the planet’s vicinity remained very cold, around 50 Kelvins, whereas in the core accretion case the circumplanetary disk was heated to several hundreds of Kelvins. «The disk instability simulations are the first that can resolve the circumplanetary disk around multiple protoplanets, using tens of millions of resolution elements in the computational domain. We exploited Piz Daint to accelerate the calculations using Graphics Processing Units (GPUs)” adds Mayer.

This huge temperature difference is easily observable. «When astronomers look into new forming planetary systems, just measuring the temperatures in the planet’s vicinity will be enough to tell which formation mechanism built the given planet,» explains Judit Szulágyi. A first comparison of the calculated and observed data seems to favour the core accretion theory. Another difference that was expected didn’t show up in the computer simulation. Before, astrophysics thought that the circumplanetary disk significantly differs in mass in the two formation scenarios. «We showed that this is not true,» says the PlanetS member.

Luminous shock front detected

Regarding the size of the new born planet, observations can be misleading as the astrophysicist found in a second study together with Christoph Mordasini, Professor at the University of Bern. In the core accretion model the researchers had a closer look at the disk around planets with masses three to ten times bigger than Jupiter’s. The computer simulations showed that gas falling on the disk from the outside heats up and creates a very luminous shock front on the disk’s upper layer. This significantly alters the observational appearance of young, forming planets.

«When we see a luminous spot inside a circumplanetary disk, we cannot be sure whether we see the planet luminosity, or also the surrounding disk luminosity,» says Judit Szulágyi. This may lead to an overestimation of the planet’s mass of up to four times. «So maybe an observed planet has only the same mass as Saturn instead of some Jupiter masses,» concludes the scientist.

In their simulations the astrophysicists mimicked the formation processes by using the basic physical laws such as gravity or the hydrodynamical equations of the gas. Because of the complexity of the physical models the simulations were very time consuming, even on Europe’s fastest supercomputer at CSCS: «On the order of nine months running time on hundreds to several thousands of computing cores» estimates Judit Szulágyi: «This means that on one computing core it would have taken longer than my entire lifetime.»

Yet there are still challenges ahead. Simulations of disk instability still do not cover a long timescale. It is possible that after the protoplanet has collapsed to the density of Jupiter its disk will heat up more like in core-accretion. Likewise, the hotter gas found in the core-accretion case would be partially ionized, a favourable environment for effects of magnetic fields, completely neglected so far. Running even more expensive simulations with a richer description of the physics will be the next step. (bva)


Publications:

Szulagyi; L. Mayer; T. Quinn: Circumplanetary disks around young giant planets: a comparison between core-accretion and disk instability, Monthly Notices of the Royal Astronomical Society 2016;

Szulagyi; C. Mordasini: Thermodynamics of Giant Planet Formation: Shocking Hot Surfaces on Circumplanetary Disks, Monthly Notices of the Royal Astronomical Society: Letters 2016;


Contact:

Dr. Judit Szulágyi
ETH Zürich, Switzerland
Phone +41 44 633 76 75
judit.szulagyi@phys.ethz.ch


Friday, October 28, 2016

Youthful NGC 362

Credit: ESA/Hubble & NASA


Globular clusters offer some of the most spectacular sights in the night sky. These ornate spheres contain hundreds of thousands of stars, and reside in the outskirts of galaxies. The Milky Way contains over 150 such clusters — and the one shown in this NASA/ESA Hubble Space Telescope image, named NGC 362, is one of the more unusual ones.

As stars make their way through life they fuse elements together in their cores, creating heavier and heavier elements — known in astronomy as metals — in the process. When these stars die, they flood their surroundings with the material they have formed during their lifetimes, enriching the interstellar medium with metals. Stars that form later therefore contain higher proportions of metals than their older relatives.

By studying the different elements present within individual stars in NGC 362, astronomers discovered that the cluster boasts a surprisingly high metal content, indicating that it is younger than expected. Although most globular clusters are much older than the majority of stars in their host galaxy, NGC 362 bucks the trend, with an age lying between 10 and 11 billion years old. For reference, the age of the Milky Way is estimated to be above 13 billion years.

This image, in which you can view NGC 362’s individual stars, was taken by Hubble’s Advanced Camera for Surveys (ACS).




Thursday, October 27, 2016

NASA Missions Harvest a Passel of ‘Pumpkin’ Stars

Astronomers using observations from NASA's Kepler and Swift missions have discovered a batch of rapidly spinning stars that produce X-rays at more than 100 times the peak levels ever seen from the sun. The stars, which spin so fast they've been squashed into pumpkin-like shapes, are thought to be the result of close binary systems where two sun-like stars merge.

Dive into the Kepler field and learn more about the origins of these rapidly spinning stars.
Credits: NASA's Goddard Space Flight Center/Scott Wiessinger, producer


"These 18 stars rotate in just a few days on average, while the sun takes nearly a month," said Steve Howell, a senior research scientist at NASA's Ames Research Center in Moffett Field, California, and leader of the team. "The rapid rotation amplifies the same kind of activity we see on the sun, such as sunspots and solar flares, and essentially sends it into overdrive."

The most extreme member of the group, a K-type orange giant dubbed KSw 71, is more than 10 times larger than the sun, rotates in just 5.5 days, and produces X-ray emission 4,000 times greater than the sun does at solar maximum.

This artist's concept illustrates how the most extreme "pumpkin star" found by Kepler and Swift compares with the sun. Both stars are shown to scale. KSw 71 is larger, cooler and redder than the sun and rotates four times faster. Rapid spin causes the star to flatten into a pumpkin shape, which results in brighter poles and a darker equator. Rapid rotation also drives increased levels of stellar activity such as starspots, flares and prominences, producing X-ray emission over 4,000 times more intense than the peak emission from the sun. KSw 71 is thought to have recently formed following the merger of two sun-like stars in a close binary system.Credits: NASA's Goddard Space Flight Center/Francis Reddy

These rare stars were found as part of an X-ray survey of the original Kepler field of view, a patch of the sky comprising parts of the constellations Cygnus and Lyra. From May 2009 to May 2013, Kepler measured the brightness of more than 150,000 stars in this region to detect the regular dimming from planets passing in front of their host stars. The mission was immensely successful, netting more than 2,300 confirmed exoplanets and nearly 5,000 candidates to date. An ongoing extended mission, called K2, continues this work in areas of the sky located along the ecliptic, the plane of Earth's orbit around the sun.

"A side benefit of the Kepler mission is that its initial field of view is now one of the best-studied parts of the sky," said team member Padi Boyd, a researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who designed the Swift survey. For example, the entire area was observed in infrared light by NASA's Wide-field Infrared Survey Explorer, and NASA's Galaxy Evolution Explorer observed many parts of it in the ultraviolet. "Our group was looking for variable X-ray sources with optical counterparts seen by Kepler, especially active galaxies, where a central black hole drives the emissions," she explained.

Using the X-ray and ultraviolet/optical telescopes aboard Swift, the researchers conducted the Kepler–Swift Active Galaxies and Stars Survey (KSwAGS), imaging about six square degrees, or 12 times the apparent size of a full moon, in the Kepler field.

"With KSwAGS we found 93 new X-ray sources, about evenly split between active galaxies and various types of X-ray stars," said team member Krista Lynne Smith, a graduate student at the University of Maryland, College Park who led the analysis of Swift data. "Many of these sources have never been observed before in X-rays or ultraviolet light."

For the brightest sources, the team obtained spectra using the 200-inch telescope at Palomar Observatory in California. These spectra provide detailed chemical portraits of the stars and show clear evidence of enhanced stellar activity, particularly strong diagnostic lines of calcium and hydrogen.

The researchers used Kepler measurements to determine the rotation periods and sizes for 10 of the stars, which range from 2.9 to 10.5 times larger than the sun. Their surface temperatures range from somewhat hotter to slightly cooler than the sun, mostly spanning spectral types F through K. Astronomers classify the stars as subgiants and giants, which are more advanced evolutionary phases than the sun's caused by greater depletion of their primary fuel source, hydrogen. All of them eventually will become much larger red giant stars.

A paper detailing the findings will be published in the Nov. 1 edition of the Astrophysical Journal and is now available online.

Forty years ago, Ronald Webbink at the University of Illinois, Urbana-Champaign noted that close binary systems cannot survive once the fuel supply of one star dwindles and it starts to enlarge. The stars coalesce to form a single rapidly spinning star initially residing in a so-called "excretion" disk formed by gas thrown out during the merger. The disk dissipates over the next 100 million years, leaving behind a very active, rapidly spinning star.

Howell and his colleagues suggest that their 18 KSwAGS stars formed by this scenario and have only recently dissipated their disks. To identify so many stars passing through such a cosmically brief phase of development is a real boon to stellar astronomers.

"Webbink's model suggests we should find about 160 of these stars in the entire Kepler field," said co-author Elena Mason, a researcher at the Italian National Institute for Astrophysics Astronomical Observatory of Trieste. "What we have found is in line with theoretical expectations when we account for the small portion of the field we observed with Swift."

The team has already extended their Swift observations to additional fields mapped by the K2 mission.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corp. operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

Goddard manages the Swift mission in collaboration with Pennsylvania State University in University Park, the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Virginia. Other partners include the University of Leicester and Mullard Space Science Laboratory in the United Kingdom, Brera Observatory and the Italian Space Agency in Italy, with additional collaborators in Germany and Japan.


Related Links

Editor: Rob Garner




A Dead Star's Ghostly Glow

The eerie glow of a dead star, which exploded long ago as a supernova, reveals itself in this NASA Hubble Space Telescope image of the Crab Nebula. But don't be fooled. The ghoulish-looking object still has a pulse. Buried at its center is the star's tell-tale heart, which beats with rhythmic precision.

Astronomers discovered a real "tell-tale heart" in space, 6,500 light-years from Earth. The "heart" is the crushed core of a long-dead star, called a neutron star, which exploded as a supernova and is now still beating with rhythmic precision. Evidence of its heartbeat are rapid-fire, lighthouse-like pulses of energy from the fast-spinning neutron star. The stellar relic is embedded in the center of the Crab Nebula, the expanding, tattered remains of the doomed star. Credits: NASA and ESA, Acknowledgment: M. Weisskopf/Marshall Space Flight Center

This time-lapse movie of the Crab Nebula, made from NASA Hubble Space Telescope observations, reveals wave-like structures expanding outward from the "heart" of an exploded star. The waves look like ripples in a pond. The heart is the crushed core of the exploded star, or supernova. Called a neutron star, it has about the same mass as the sun but is squeezed into an ultra-dense sphere that is only a few miles across and 100 billion times stronger than steel. This surviving relic is a tremendous dynamo, spinning 30 times a second. The rapidly spinning neutron star is visible in the image as the bright object just below center. The bright object to the left of the neutron star is a foreground or background star. The movie is assembled from 10 Hubble exposures taken between September and November 2005 by the Advanced Camera for Surveys.  Credits: NASA and ESA, Acknowledgment: J. Hester (Arizona State University)


The "heart" is the crushed core of the exploded star. Called a neutron star, it has about the same mass as the sun but is squeezed into an ultra-dense sphere that is only a few miles across and 100 billion times stronger than steel. The tiny powerhouse is the bright star-like object near the center of the image.
This surviving remnant is a tremendous dynamo, spinning 30 times a second. The wildly whirling object produces a deadly magnetic field that generates an electrifying 1 trillion volts. This energetic activity unleashes wisp-like waves that form an expanding ring, most easily seen to the upper right of the pulsar.

The nebula's hot gas glows in radiation across the electromagnetic spectrum, from radio to X-rays. The Hubble exposures were taken in visible light as black-and-white exposures. The Advanced Camera for Surveys made the observations between January and September 2012. The green hue has been added to give the image a Halloween theme.

The Crab Nebula is one of the most historic and intensively studied supernova remnants. Observations of the nebula date back to 1054 A.D., when Chinese astronomers first recorded seeing a "guest star" during the daytime for 23 days. The star appeared six times brighter than Venus. Japanese, Arabic, and Native American stargazers also recorded seeing the mystery star. In 1758, while searching for a comet, French astronomer Charles Messier discovered a hazy nebula near the location of the long-vanished supernova. He later added the nebula to his celestial catalog as "Messier 1," marking it as a "fake comet." Nearly a century later British astronomer William Parsons sketched the nebula. Its resemblance to a crustacean led to M1's other name, the Crab Nebula. In 1928 astronomer Edwin Hubble first proposed associating the Crab Nebula to the Chinese "guest star" of 1054.

The nebula, bright enough to be visible in amateur telescopes, is located 6,500 light-years away in the constellation Taurus.


Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
Villard@stsci.edu
410-338-4514

Editor: Karl Hille


Wednesday, October 26, 2016

ESO’s VLT Detects Unexpected Giant Glowing Halos around Distant Quasars

Bright halos around distant quasars

Videos

Bright halos around distant quasars
Bright halos around distant quasars

3D animation of quasar halo
3D animation of quasar halo




An international team of astronomers has discovered glowing gas clouds surrounding distant quasars. This new survey by the MUSE instrument on 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.

An international collaboration of astronomers, led by a group at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, has used the unrivalled observing power of MUSE on the Very Large Telescope (VLT) at ESO’s Paranal Observatory to study gas around distant active galaxies, less than two billion years after the Big Bang. These active galaxies, called quasars, contain supermassive black holes in their centres, which consume stars, gas, and other material at an extremely high rate. This, in turn, causes the galaxy centre to emit huge amounts of radiation, making quasars the most luminous and active objects in the Universe.

The study involved 19 quasars, selected from among the brightest that are observable with MUSE. 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 centres 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 team suspects this is due to the vast increase in the observing power of MUSE over previous similar instruments, but further observations are needed to determine whether this is the case.

It is still too early to say if this is due to our new observational technique or if there is something peculiar about the quasars in our sample. So there is still a lot to learn; we are just at the beginning of a new era of discoveries”, says lead author Elena Borisova, from the ETH Zurich.

The original goal of the study was to analyse the gaseous components of the Universe on the largest scales; a structure sometimes referred to as the cosmic web, in which quasars form bright nodes [1]. The gaseous components of this web are normally extremely difficult to detect, so the illuminated halos of gas surrounding the quasars deliver an almost unique opportunity to study the gas within this large-scale cosmic structure.

The 19 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.

The discovery shows the potential of MUSE for observing this type of object [2]. Co-author Sebastiano Cantalupo is very excited about the new instrument and the opportunities it provides: “We have exploited the unique capabilities of MUSE in this study, which will pave the way for future surveys. Combined with a new generation of theoretical and numerical models, this approach will continue to provide a new window on cosmic structure formation and galaxy evolution.”


 
Notes

[1] The cosmic web is the structure of the Universe at the largest scale. It is comprised of spindly filaments of primordial material (mostly hydrogen and helium gas) and dark matter which connect galaxies and span the chasms between them. The material in this web can feed along the filaments into galaxies and drive their growth and evolution.

[2] MUSE is an integral field spectrograph and combines spectrographic and imaging capabilities. It can observe large astronomical objects in their entirety in one go, and for each pixel measure the intensity of the light as a function of its colour, or wavelength.


 
More Information

This research was presented in the paper "Ubiquitous giant Lyα nebulae around the brightest quasars at z ~ 3.5 revealed with MUSE", to appear in the Astrophysical Journal.


The team is composed of Elena Borisova, Sebastiano Cantalupo, Simon J. Lilly, Raffaella A. Marino and Sofia G. Gallego (Institute for Astronomy, ETH Zurich, Switzerland), Roland Bacon and Jeremy Blaizot (University of Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Nicolas Bouché (Institut de Recherche en Astrophysique et Planétologie, Toulouse, France), Jarle Brinchmann (Leiden Observatory, Leiden, The Netherlands; Instituto de Astrofísica e Ciências do Espaço, Porto, Portugal), C Marcella Carollo (Institute for Astronomy, ETH Zurich, Switzerland), Joseph Caruana (Department of Physics, University of Malta, Msida, Malta; Institute of Space Sciences & Astronomy, University of Malta, Malta), Hayley Finley (Institut de Recherche en Astrophysique et Planétologie, Toulouse, France), Edmund C. Herenz (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Johan Richard (Univ Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Joop Schaye and Lorrie A. Straka (Leiden Observatory, Leiden, The Netherlands), Monica L. Turner (MIT-Kavli Center for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA), Tanya Urrutia (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Anne Verhamme (University of Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Lutz Wisotzki (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany).


ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.


Links



Contacts 

Elena Borisova
ETH Zurich
Switzerland
Tel: +41 44 633 77 09

Sebastiano Cantalupo
ETH Zurich
Switzerland
Tel: +41 44 633 70 57

Mathias Jäger
Public Information Officer
Garching bei München, Germany
Tel: +49 176 62397500


Source: ESO

Preferentially earth-sized-planets with lots of water

Artist’s impression of Earth-sized planets orbiting a red dwarf star.
 (Image: NASA, ESA, and G.Bacon (STScI)


Computer simulations by astrophysicists at the University of Bern of the formation of planets orbiting in the habitable zone of low mass stars such as Proxima Centauri show that these planets are most likely to be roughly the size of the Earth and to contain large amounts of water.

In August 2016, the announcement of the discovery of a terrestrial exoplanet orbiting in the habitable zone of Proxima Centauri stimulated the imagination of the experts and the general public. After all this star is the nearest star to our sun even though it is ten times less massive and 500 times less luminous. This discovery together with the one in May 2016 of a similar planet orbiting an even lower mass star (Trappist-1) convinced astronomers that such red dwarfs (as these low mass stars are called) might be hosts to a large population of Earth-like planets.

How could these objects look like? What could they be made of? Yann Alibert and Willy Benz at the Swiss NCCR PlanetS at the University of Bern carried out the first computer simulations of the formation of the population of planets expected to orbit stars ten times less massive than the sun.

“Our models succeed in reproducing planets that are similar in terms of mass and period to the ones observed recently,” Yann Alibert explains the result of the study that has been accepted for publication as a Letter in the journal “Astronomy and Astrophysics”. “Interestingly, we find that planets in close-in orbits around these type of stars are of small sizes. Typically, they range between 0.5 and 1.5 Earth radii with a peak at about 1.0 Earth radius. Future discoveries will tell if we are correct!” the researcher adds.

Ice at the bottom of the global ocean

In addition, the astrophysicists determined the water content of the planets orbiting their small host star in the habitable zone. They found that considering all the cases, around 90% of the planets are harbouring more than 10% of water. For comparison: The Earth has a fraction of water of only about 0,02%. So most of these alien planets are literally water worlds in comparison! The situation could be even more extreme if the protoplanetary disks in which these planets form live longer than assumed in the models. In any case, these planets would be covered by very deep oceans at the bottom of which, owing to the huge pressure, water would be in form of ice.

Water is required for life as we know it. So could these planets be habitable indeed? “While liquid water is generally thought to be an essential ingredient, too much of a good thing may be bad,“ says Willy Benz. In previous studies the scientists in Bern showed that too much water may prevent the regulation of the surface temperature and destabilizes the climate. “But this is the case for the Earth, here we deal with considerably more exotic planets which might be subjected to a much harsher radiation environment, and/or be in synchronous rotation,” he adds.

Following the growth of planetary embryos

To start their calculations, the scientists considered a series of a few hundreds to thousands of identical, low mass stars and around each of them a protoplanetary disk of dust and gas. Planets are formed by accretion of this material. Alibert and Benz assumed that at the beginning, in each disk there were 10 planetary embryos with an initial mass equal to the mass of the Moon. In a few day’s computer time for each system the model calculated how these randomly located embryos grew and migrated.

What kind of planets are formed depends on the structure and evolution of the protoplanetary disks. “If the protoplanetary disk lives long, then planets have a long time to migrate,” explains Yann Alibert. Before landing in the habitable zone, they started their migration beyond the so called ice line where water is frozen, and they accreted a lot of icy particles. Therefore, the overwhelming majority of these planets have a fraction of water larger than 10 %.

“Habitable or not, the study of planets orbiting very low mass stars will likely bring exciting new results, improving our knowledge of planet formation, evolution, and potential habitability,” summarizes Willy Benz. Because these stars are considerably less luminous than the sun, planets can be much closer to their star before their surface temperature becomes too high for liquid water to exist. If one considers that these type of stars also represent the overwhelming majority of stars in the solar neighbourhood and that close-in planets are presently easier to detect and study, one understands why the existence of this population of Earth-like planets is really of importance.


Publications:

Y. Alibert and W. Benz: Formation and composition of planets around very low mass stars, A&A
https://arxiv.org/abs/1610.03460

Kitzmann, Alibert et al.: The unstable CO2 feedback cycle on ocean planets, MNRAS, 2015
http://dx.doi.org/10.1093/mnras/stv1487

Alibert: A maximum radius for habitable planets, OLEB, 2015.


Contact:

Prof. Yann Alibert
University of Bern, Switzerland
yann.alibert@space.unibe.ch

Prof. Willy Benz
University of Bern, Switzerland
willy.benz@space.unibe.ch



Tuesday, October 25, 2016

'Heartbeat Stars' Unlocked in New Study


Editor: Tony Greicius



Monday, October 24, 2016

Tracking Waves from Sunspots Gives New Solar Insight

Scientists used data from NASA’s Solar Dynamics Observatory, NASA’s Interface Region Imaging Spectrograph, and the Big Bear Solar Observatory to track a solar wave as it channeled upwards from the sun’s surface into the atmosphere. Credits: Zhao et al/NASA/SDO/IRIS/BBSO. Hi-res image
 
Scientists analyzed sunspot images from a trio of observatories -- including the Big Bear Solar Observatory, which captured this footage -- to make the first-ever observations of a solar wave traveling up into the sun’s atmosphere from a sunspot. Credits: BBSO/Zhao et al
 
 
Tracking solar waves like this provides a novel tool for scientists to study the atmosphere of the sun. The imagery of the journey also confirms existing ideas, helping to nail down the existence of a mechanism that moves energy – and therefore heat – into the sun’s mysteriously-hot upper atmosphere, called the corona. A study on these results was published Oct. 11, 2016, in The Astrophysical Journal Letters.

“We see certain kinds of solar seismic waves channeling upwards into the lower atmosphere, called the chromosphere, and from there, into the corona,” said Junwei Zhao, a solar scientist at Stanford University in Stanford, California, and lead author on the study. “This research gives us a new viewpoint to look at waves that can contribute to the energy of the atmosphere.”

The study makes use of the wealth of data captured by NASA’s Solar Dynamics Observatory, NASA’s Interface Region Imaging Spectrograph, and the Big Bear Solar Observatory in Big Bear Lake, California. Together, these observatories watch the sun in 16 wavelengths of light that show the sun’s surface and lower atmosphere. SDO alone captures 11 of these.

“SDO takes images of the sun in many different wavelengths at a high time resolution,” said Dean Pesnell, SDO project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That lets you see the frequencies of these waves – if you didn’t have such rapid-fire images, you’d lose track of the waves from one image to the next.”

Though scientists have long suspected that the waves they spot in the sun’s surface, called the photosphere, are linked to those seen in the lowest reaches of the sun’s atmosphere, called the chromosphere, this new analysis is the first time that scientists have managed to actually watch the wave travel up through the various layers into the sun’s atmosphere.

When material is heated to high temperatures, it releases energy in the form of light. The type, or wavelength, of that light is determined by what the material is, as well as its temperature.  That means different wavelengths from the sun can be mapped to different temperatures of solar material. Since we know how the sun’s temperature changes throughout the layers of its atmosphere, we can then order these wavelengths according to their height above the surface – and essentially watch solar waves as they travel upwards.

The implications of this study are twofold – first, this technique for watching the waves itself gives scientists a new tool to understand the sun’s lower atmosphere.

“Watching the waves move upwards tells us a lot about the properties of the atmosphere above sunspots – like temperature, pressure, and density,” said Ruizhu Chen, a graduate student scientist at Stanford who is an author on the study. “More importantly, we can figure out the magnetic field strength and direction.”
 
The effect of the magnetic field on these waves is pronounced. Instead of traveling straight upwards through the sun, the waves veer off, taking a curved path through the atmosphere.

“The magnetic field is acting like railroad tracks, guiding the waves as they move up through the atmosphere,” said Pesnell, who was not involved in this study.

The second implication of this new research is for a long-standing question in solar physics – the coronal heating problem.

The sun produces energy by fusing hydrogen at its core, so the simplest models suggest that each layer of the sun should be cooler as you move outward. However, the sun’s atmosphere, called the corona, is about a hundred times hotter than the region below – counter to what you would expect.

No one has as-yet been able to definitively pinpoint the source of all the extra heat in the corona, but these waves may play a small role.

“When a wave travels upwards, a number of different things can happen,” said Zhao. “Some may reflect back downwards, or contribute to heating – but by how much, we don’t yet know.”

NASA Goddard built, operates and manages the SDO spacecraft for NASA's Science Mission Directorate in Washington. Lockheed Martin designed the IRIS observatory and manages the mission for NASA. The Big Bear Solar Observatory is operated by the New Jersey Institute of Technology in Newark, New Jersey.

Related:

By Sarah Frazier 
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Editor: Karl Hille


Source: NASA/Sun

Saturday, October 22, 2016

Long-term, hi-res tracking of eruptions on Jupiter’s moon, Io

Images of Io at different near-infrared wavelengths show bright spots that are thermal emissions from the moon’s myriad volcanoes. Click on image to see the entire set, with the name of the near-infrared filter indicated in the black box at the start of each section. Note the increasing number of hot spots detected at longer wavelengths, i.e. towards the bottom of the figure. (Katherine de Kleer and Imke de Pater image, from Gemini Observatory/AURA & Keck Observatory).

All hot spots detected are shown on a map of Io. Each circle represents a new detection; the size of the circle corresponds logarithmically to the intensity, and more opaque regions are where a hot spot was detected multiple times. The color and symbol indicate the type of eruption, following the legend. Loki Patera is at 310 West, 10 North and Kurdalagon Patera is at 220 West, 50 South.

Video showing all hot spots detected from August 2013 through December 2015, displayed on a full map of Io and illustrating the approximate length of time they were visible. The size of the circle corresponds logarithmically to the intensity. Loki Patera is at 310 West longitude, 10 North latitude and Kurdalagon Patera is at 220 West longitude, 50 South latitude. (Credit: Katherine de Kleer and Imke de Pater, UC Berkeley). Youtube

High-resolution image of Io, showing hot spots — Loki Patera and Amaterasu Patera — visible from Earth only with adaptive optics on the planet’s largest telescopes, Keck and Gemini.



Press release issued by the University of Berkeley to coincide with presentation at the joint 48th annual meeting of the Division for Planetary Sciences (DPS) of the American Astronomical Society (AAS) and 11th annual European Planetary Science Congress (EPSC).

Jupiter’s moon Io continues to be the most volcanically active body in the solar system, as documented by the longest series of frequent, high-resolution observations of the moon’s thermal emission ever obtained.

Using near-infrared adaptive optics on two of the world’s largest telescopes — the 10-meter Keck II and the 8-meter Gemini North, both located near the summit of the dormant volcano Mauna Kea in Hawaii — University of California, Berkeley, astronomers tracked 48 volcanic hotspots on the surface over a period of 29 months from 2013 through the end of 2015.

Without adaptive optics — a technique that removes the atmospheric blur to sharpen the image — Io is merely a fuzzy ball. Adaptive optics can separate features just a few hundred kilometers apart on Io’s 3,600-kilometer diameter surface.

“On a given night, we may see half a dozen or more different hot spots,” said Katherine de Kleer, a UC Berkeley graduate student who led the observations. “Of Io’s hundreds of active volcanoes, we have been able to track the 50 that were the most powerful over the past few years.”

She and Imke de Pater, a UC Berkeley professor of astronomy and of Earth and planetary science, observed the heat coming off of active eruptions as well as cooling lava flows and were able to determine the temperature and total power output of individual volcanic eruptions, as well as track their evolution over days, weeks and sometimes even years.

Interestingly, some of the eruptions appeared to progress across the surface over time, as if one triggered another 500 kilometers away.

“While it stretches the imagination to devise a mechanism that could operate over distances of 500 kilometers, Io’s volcanism is far more extreme than anything we have on Earth and continues to amaze and baffle us,” de Kleer said.

De Kleer and de Pater will discuss their observations at a media briefing on Oct. 20 during the joint 48th meeting of the American Astronomical Society’s Division for Planetary Sciences and 11th European Planetary Science Congress in Pasadena, California. Papers describing the observations have been accepted for future publication by the journal Icarus.

Tidal Heating

Io’s intense volcanic activity is powered by tidal heating: heating from friction generated in Io’s interior as Jupiter’s intense gravitational pull changes by small amounts along Io’s orbit. Models for how this heating occurs predict that most of Io’s total volcanic power should be emitted either near the poles or near the equator, depending on the model, and that the pattern should be symmetric between the forward- and backward-facing hemispheres in Io’s orbit (that is, at longitudes 0-180 vs. 180-360).

That’s not what they saw. Over the observational period, August 2013 through December 2015, the team obtained images of Io on 100 nights. Though they saw a surprising number of short-lived but intense eruptions that appeared suddenly and subsided in a matter of days, every single one took place on the trailing face of Io (between 180 and 360 degrees longitude) rather than the leading face, and at higher latitudes than more typical eruptions.

“The distribution of the eruptions is a poor match to the model predictions,” de Kleer said, “but future observations will tell us whether this is just because the sample size is too small, or because the models are too simplified. Or, perhaps we’ll learn that local geological factors play a much greater role in determining where and when the volcanoes erupt than the physics of tidal heating do.”

One key target of interest was Io’s most powerful persistent volcano, Loki Patera, which brightens by more than a factor of 10 every 1-2 years. A patera is an irregular crater, usually volcanic.

Many scientists believe that Loki Patera is a massive lava lake, and that these bright episodes represent its overturning crust, like that seen in lava lakes on Earth. In fact, the heat emissions from Loki Patera appear to travel around the lake during each event, as if from a wave moving around a lake triggering the destabilization and sinking of portions of crust. Prior to 2002, this front seemed to travel around the cool island in the center of the lake in a counter-clockwise direction.

After an apparent cessation of brightening events after 2002, de Pater observed renewed activity in 2009.

“With the renewed activity, the waves traveled clockwise around the lava lake,” she noted.

Another volcano, Kurdalagon Patera, produced unusually hot eruptions twice in the spring of 2015, coinciding with the brightening of an extended cloud of neutral material that orbits Jupiter. This provides circumstantial evidence that eruptions on the surface are the source of variability in this neutral cloud, though it’s unclear why other eruptions were not also associated with brightening, de Kleer said.

De Kleer noted that the Keck and Gemini telescopes, both atop the dormant volcano Mauna Kea, complement one another. Gemini North’s queue scheduling allowed more frequent observations — often several a week — while Keck’s instruments are sensitive also to longer wavelengths (5 microns), showing cooler features such as older lava flows that are invisible in the Gemini observations.

The astronomers are continuing their frequent observations of Io, providing a long-term database of high spatial resolution images that not even Galileo, which orbited Jupiter for eight years, was able to achieve.



Media Contacts:
 
Robert Sanders
UCB Media Relations
+1 510-643-6998
rlsanders@berkeley.edu

Anita Heward
EPSC Press Officer
+44 (0)77 5603 4243

anita.heward@europlanet-eu.org

Science Contacts:
 
Katherine de Kleer
kdekleer@berkeley.edu

Imke de Pater
imke@berkeley.edu



References:

* “Time Variability of Io’s Volcanic Activity from Near-IR Adaptive Optics Observations on 100 Nights in 2013-2015” (accepted by Icarus).
* “Spatial Distribution of Io’s Volcanic Activity from Near-IR Adaptive Optics Observations on 100 Nights in 2013-2015” (accepted by Icarus).

Further information:

The joint 48th meeting of the Division for Planetary Sciences (DPS) and 11th European Planetary Science Congress (EPSC) in Pasadena, California, is second time DPS and EPSC have been joined into one meeting. The goal of the joint meeting is to strengthen international scientific collaboration in all areas of planetary science. This is the first time that EPSC, which provides the dissemination platform for the Europlanet 2020 Research Infrastructure, is held outside Europe. For more information, see: https://aas.org/meetings/dps48. Follow: #dpsepsc, @DPSMeeting, @europlanetmedia, and @AAS_Press on Twitter.


Source: Europlanet

Friday, October 21, 2016

The Toucan and the cluster

Credit: ESA/Hubble & NASA



It may be famous for hosting spectacular sights such as the Tucana Dwarf Galaxy and 47 Tucanae (heic1510), the second brightest globular cluster in the night sky, but the southern constellation of Tucana (The Toucan) also possesses a variety of unsung cosmic beauties.

One such beauty is NGC 299, an open star cluster located within the Small Magellanic Cloud just under 200 000 light-years away. Open clusters such as this are collections of stars weakly bound by the shackles of gravity, all of which formed from the same massive molecular cloud of gas and dust. Because of this, all the stars have the same age and composition, but vary in their mass because they formed at different positions within the cloud.

This unique property not only ensures a spectacular sight when viewed through a sophisticated instrument attached to a telescope such as Hubble’s Advanced Camera for Surveys, but gives astronomers a cosmic laboratory in which to study the formation and evolution of stars — a process that is thought to depend strongly on a star’s mass.



Thursday, October 20, 2016

NGC 5128: Mysterious Cosmic Objects Erupting in X-rays Discovered

NGC 5128
Credit: NASA/CXC/UA/J.Irwin et al.  



A Tour of IC 2497




This image shows the location of a remarkable source that dramatically flares in X-rays unlike any ever seen. Along with another similar source found in a different galaxy, these objects may represent an entirely new phenomenon, as reported in our latest press release [link to PR].

These two objects were both found in elliptical galaxies, NGC 5128 (also known as Centaurus A) shown here and NGC 4636. In this Chandra X-ray Observatory image of NGC 5128, low, medium, and high-energy X-rays are colored red, green, and blue, and the location of the flaring source is outlined in the box to the lower left.

Both of these mysterious sources flare dramatically - becoming a hundred times brighter in X-rays in about a minute before steadily returning to their original X-ray levels about an hour later. At their X-ray peak, these objects qualify as ultraluminous X-ray sources (ULXs) that give off hundreds to thousands of times more X-rays than typical X-ray binary systems where a star is orbiting a black hole or neutron star.

Five flares were detected from the source located near NGC 5128, which is at a distance of about 12 million light years from Earth. A movie showing the average change in X-rays for the three flares with the most complete Chandra data, covering both the rise and fall, is shown in the inset.

The source associated with the elliptical galaxy NGC 4636, which is located about 47 million light years away, was observed to flare once.

The only other objects known to have such rapid, bright, repeated flares involve young neutron stars such as magnetars, which have extremely powerful magnetic fields. However, these newly flaring sources are found in populations of much older stars. Unlike magnetars, the new flaring sources are likely located in dense stellar environments, one in a globular cluster and the other in a small, compact galaxy.

When they are not flaring, these newly discovered sources appear to be normal binary systems where a black hole or neutron star is pulling material from a companion star similar to the Sun. This indicates that the flares do not significantly disrupt the binary system.

While the nature of these flares is unknown, the team has begun to search for answers. One idea is that the flares represent episodes when matter pulled away from a companion star falls rapidly onto a black hole or neutron star. This could happen when the companion makes its closest approach to the compact object in an eccentric orbit. Another explanation could involve matter falling onto an intermediate-mass black hole, with a mass of about 800 times that of the Sun for one source and 80 times that of the Sun for the other.

This result is describing in a paper appearing in the journal Nature on October 20, 2016. The authors are Jimmy Irwin (University of Alabama), Peter Maksym (Harvard-Smithsonian Center for Astrophysics), Gregory Sivakoff (University of Alberta), Aaron Romanowsky (San Jose State University), Dacheng Lin (University of New Hampshire), Tyler Speegle, Ian Prado, David Mildebrath (University of Alabama), Jay Strader (Michigan State University), Jifeng Lui (Chinese Academy of Sciences), and Jon Miller (University of Michigan).

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.



Fast Facts for NGC 5128:

Scale: Main image is 16.7 arcmin across (about 58,000 light years); Inset image is 1 arcmin across (about 3,500 light years)
Category: Quasars & Active Galaxies
Coordinates (J2000): RA 13h 25m 52.7s | Dec -43° 05' 46.00"
Constellation: Centaurus
Observation Date: 21 pointings between 05 Dec 1999 and 29 Aug 2012
Observation Time: 229 hours 57 min (9 days 13 hours 57 min).
Obs. ID: 316, 962, 2978, 3965, 7797-7799, 7800, 8489, 8490, 10722, 10723, 10724-10726, 11846, 11847, 12155, 12156, 13303, 13304
Instrument: ACIS
Also Known As: Centaurus A, Cen A
References: Irwin, J. et al, 2016, Nature (in press)
Color Code: X-ray (Red, Green, Blue)
Distance Estimate: 12 million light years


Wednesday, October 19, 2016

Highest Resolution Image of Eta Carinae

Detailed look on Eta Carinae

Highest resolution image of Eta Carinae

Digitized Sky Survey Image of Eta Carinae Nebula

The Carina Nebula in the constellation of Carina 

Panoramic view of the WR 22 and Eta Carinae regions of the Carina Nebula*

One Picture, Many Stories

The Carina Nebula imaged by the VLT Survey Telescope 

Eta Carinae 



Videos

Zoom on Eta Carinae
Zoom on Eta Carinae

Animation of Eta Carinae and its surrounding
Animation of Eta Carinae and its surrounding





VLT Interferometer captures raging winds in famous massive stellar system


An international team of astronomers have used the Very Large Telescope Interferometer to image the Eta Carinae star system in the greatest detail ever achieved. They found new and unexpected structures within the binary system, including in the area between the two stars where extremely high velocity stellar winds are colliding. These new insights into this enigmatic star system could lead to a better understanding of the evolution of very massive stars.

Led by Gerd Weigelt from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, a team of astronomers have used the Very Large Telescope Interferometer (VLTI) at ESO’s Paranal Observatory to take a unique image of the Eta Carinae star system in the Carina Nebula.

This colossal binary system consists of two massive stars orbiting each other and is very active, producing stellar winds which travel at velocities of up to ten million kilometres per hour [1]. The zone between the two stars where the winds from each collide is very turbulent, but until now it could not be studied.

The power of the Eta Carinae binary pair creates dramatic phenomena. A “Great Eruption” in the system was observed by astronomers in the 1830s. We now know that this was caused by the larger star of the pair expelling huge amounts of gas and dust in a short amount of time, which led to the distinctive lobes, known as the Homunculus Nebula, that we see in the system today. The combined effect of the two stellar winds as they smash into each other at extreme speeds is to create temperatures of millions of degrees and intense deluges of X-ray radiation.

The central area where the winds collide is so comparatively tiny — a thousand times smaller than the Homunculus Nebula — that telescopes in space and on the ground so far have not been able to image them in detail. The team has now utilised the powerful resolving ability of the VLTI instrument AMBER to peer into this violent realm for the first time. A clever combination — an interferometer — of three of the four Auxiliary Telescopes at the VLT lead to a tenfold increase in resolving power in comparison to a single VLT Unit Telescope. This delivered the sharpest ever image of the system and yielded unexpected results about its internal structures.

The new VLTI image clearly depict the structure which exists between the two Eta Carinae-stars. An unexpected fan-shaped structure was observed where the raging wind from the smaller, hotter star crashes into the denser wind from the larger of the pair.

Our dreams came true, because we can now get extremely sharp images in the infrared. The VLTI provides us with a unique opportunity to improve our physical understanding of Eta Carinae and many other key objects”, says Gerd Weigelt.

In addition to the imaging, the spectral observations of the collision zone made it possible to measure the velocities of the intense stellar winds [2]. Using these velocities, the team of astronomers were able to produce more accurate computer models of the internal structure of this fascinating stellar system, which will help increase our understanding of how these kind of extremely high mass stars lose mass as they evolve.

Team member Dieter Schertl (MPIfR) looks forward: “The new VLTI instruments GRAVITY and MATISSE will allow us to get interferometric images with even higher precision and over a wider wavelength range. This wide wavelength range is needed to derive the physical properties of many astronomical objects.



Notes

[1] The two stars are so massive and bright that the radiation they produce rips off their surfaces and spews them into space. This expulsion of stellar material is referred to as stellar “wind”, and it can travel at millions of kilometres per hour.

[2] Measurements were done through the Doppler effect. Astronomers use the Doppler effect (or shifts) to calculate precisely how fast stars and other astronomical objects move toward or away from Earth. The movement of an object towards or away from us causes a slight shift in its spectral lines. The velocity of the motion can be calculated from this shift.



 More Information


This research was presented in a paper to appear in Astronomy and Astrophysics.

The team is composed of G. Weigelt (Max Planck Institute for Radio Astronomy, Germany), K.-H. Hofmann (Max Planck Institute for Radio Astronomy, Germany), D. Schertl (Max Planck Institute for Radio Astronomy, Germany), N. Clementel (South African Astronomical Observatory, South Africa) , M.F. Corcoran (Goddard Space Flight Center, USA; Universities Space Research Association, USA), A. Damineli (Universidade de São Paulo, Brazil ), W.-J. de Wit (European Southern Observatory, Chile), R. Grellmann (Universität zu Köln, Germany), J. Groh (The University of Dublin, Ireland ), S. Guieu (European Southern Observatory, Chile), T. Gull (Goddard Space Flight Center, USA), M. Heininger (Max Planck Institute for Radio Astronomy, Germany) , D.J. Hillier (University of Pittsburgh, USA), C.A. Hummel (European Southern Observatory, Germany), S. Kraus (University of Exeter, UK), T. Madura (Goddard Space Flight Center, USA), A. Mehner (European Southern Observatory, Chile), A. Mérand ( European Southern Observatory, Chile), F. Millour (Université de Nice Sophia Antipolis, France), A.F.J. Moffat (Université de Montréal, Canada), K. Ohnaka (Universidad Católica del Norte, Chile), F. Patru (Osservatorio Astrofisico di Arcetri, Italy), R.G. Petrov (Université de Nice Sophia Antipolis, France), S. Rengaswamy (Indian Institute of Astrophysics, India) , N.D. Richardson (The University of Toledo, USA), T. Rivinius (European Southern Observatory, Chile), M. Schöller (European Southern Observatory, Germany), M. Teodoro (Goddard Space Flight Center, USA) , and M. Wittkowski (European Southern Observatory, Germany)

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.



Links



Contacts

Gerd Weigelt
Max-Planck-Institut für Radioastronomie
Bonn, Germany
Tel: +49 228 525 243
Email: weigelt@mpifr-bonn.mpg.de

Dieter Schertl
Max-Planck-Institut für Radioastronomie
Bonn, Germany
Tel: +49 228 525 301
Email: ds@mpifr-bonn.mpg.de

Norbert Junkes
Public Information Officer, Max-Planck-Institut für Radioastronomie
Bonn, Germany
Tel: +49 228 525 399
Email: njunkes@mpifr-bonn.mpg.de

Mathias Jäger
Public Information Officer
Garching bei München, Germany
Tel: +49 176 62397500
Email: mjaeger@partner.eso.org

Source: ESO