Max Planck Institute for Astronomy

Heidelberg, Germany

Max Planck Institute for Astronomy

Heidelberg, Germany

For similarly named astronomy institutes, see: Institute of Astronomy.The Max-Planck-Institut für Astronomie is a research institute of the Max Planck Society. It is located in Heidelberg, Baden-Württemberg, Germany near the top of the Koenigstuhl, adjacent to the historic Landessternwarte Heidelberg-Königstuhl astronomical observatory.The institute was founded in 1967. Its founding directors were H. Elsässer, and G. Munch, who was followed by S. V. W. Beckwith. The current directors are Hans-Walter Rix and Thomas Henning. G. H. Herbig, Karl-Heinz B\"ohm, Immo Appenzeller, Willy Benz, and Rafael Rebolo have been external scientific members. Wikipedia.


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News Article | May 11, 2017
Site: www.futurity.org

In the vast expanses between galaxies, only atoms—a haze of hydrogen gas left over from the Big Bang—occupy solitary cubes one meter on a side. On the largest scale, this diffuse material forms a network of filamentary structures known as the “cosmic web,” its tangled strands spanning billions of light years and accounting for the majority of atoms in the universe. Now, a team of astronomers has made the first measurements of small-scale ripples in this primeval hydrogen gas using rare double quasars. Although the regions of cosmic web they studied lie nearly 11 billion light years away, they were able to measure variations in its structure on scales 100,000 times smaller, comparable to the size of a single galaxy. The results appear in the journal Science. Intergalactic gas is so tenuous that it emits no light of its own. Instead astronomers study it indirectly by observing how it selectively absorbs the light coming from faraway sources known as quasars. Quasars constitute a brief hyperluminous phase of the galactic life cycle powered by matter falling into a galaxy’s central supermassive black hole. Acting like cosmic lighthouses, they are bright, distant beacons that allow astronomers to study intergalactic atoms residing between the location of the quasar and the Earth. But because these hyperluminous episodes last only a tiny fraction of a galaxy’s lifetime, quasars are correspondingly rare and are typically separated from each other by hundreds of millions of light years. In order to probe the cosmic web on much smaller length scales, the astronomers exploited a fortuitous cosmic coincidence: They identified exceedingly rare pairs of quasars and measured subtle differences in the absorption of intergalactic atoms along the two sightlines. “Pairs of quasars are like needles in a haystack,” explains Joseph Hennawi, an associate professor in the University of California, Santa Barbara’s physics department who pioneered the application of algorithms from machine learning to efficiently locate quasar pairs in the massive amounts of data produced by digital imaging surveys of the night sky. “In order to find them, we combed through images of billions of celestial objects millions of times fainter than what the naked eye can see,” he says. Once identified, researchers observed the quasar pairs with the largest telescopes in the world, including the 10-meter Keck telescopes at the W.M. Keck Observatory on Mauna Kea, Hawaii. “One of the biggest challenges was developing the mathematical and statistical tools to quantify the tiny differences we measured in this new kind of data,” says lead author Alberto Rorai, Hennawi’s former PhD student who is now a postdoctoral researcher at Cambridge University. Rorai developed these tools as part of the research for his doctoral degree and applied them to spectra of quasars with Hennawi and other colleagues. The astronomers compared their measurements to supercomputer models that simulate the formation of cosmic structures from the Big Bang to the present. On a single laptop, these complex calculations would require almost 1,000 years to complete, but modern supercomputers enabled the researchers to carry them out in just a few weeks. “The input to our simulations are the laws of physics and the output is an artificial universe, which can be directly compared to astronomical data,” says coauthor Jose Oñorbe, a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany, who led the supercomputer simulation effort. “I was delighted to see that these new measurements agree with the well-established paradigm for how cosmic structures form.” “One reason why these small-scale fluctuations are so interesting is that they encode information about the temperature of gas in the cosmic web just a few billion years after the Big Bang,” explains Hennawi. Astronomers believe that the matter in the universe went through phase transitions billions of years ago, which dramatically changed its temperature. Known as cosmic re-ionization, these transitions occurred when the collective ultraviolet glow of all stars and quasars in the universe became intense enough to strip electrons off atoms in intergalactic space. How and when re-ionization occurred is one of the biggest open questions in the field of cosmology, and these new measurements provide important clues that will help narrate this chapter of cosmic history.


News Article | May 12, 2017
Site: news.yahoo.com

Quasars (short for quasi-stellar radio sources) have been objects of intrigue for astronomers ever since they were first detected in the 1960s. A quasar is a compact region with a supermassive black hole at its centre, heated to such an extent that it emits massive amounts of energy — briefly outshining the galaxy in which it resides. Our current understanding tells us that for a supermassive black hole to turn into a massive quasar, it would need to accrete matter for at least 100 million years. This means the odds of finding such an object in the early years of the universe are extremely low. However, a team of astronomers has now discovered three ancient quasars that seemingly challenge the conventional wisdom. All of these quasars formed just over a billion years after the universe’s birth, but have still — through an as-of-yet inexplicable mechanism — managed to accumulate the mass of about a billion sons. For comparison, Sagittarius A* — the supermassive black hole at the centre of our galaxy — is merely four million times the mass of the sun. “This is a surprising result,” Christina Eilers, a doctoral student at Max Planck Institute for Astronomy and lead author of a study detailing the observations, said in a statement. “We don’t understand how these young quasars could have grown the supermassive black holes that power them in such a short time.” In order to calculate the age of these quasars, the astronomers examined how these objects had influenced their “proximity zones” — which are hot, mostly-transparent regions rich in ionized gas around quasars. Once a supermassive black hole turns into a quasar, its proximity zone grows very quickly, and by observing how big this zone is, scientists can estimate the duration the quasar has been active for. For these three quasars, however, the proximity zones were very small, indicating they had been active for only about 100,000 years. "No current theoretical models can explain the existence of these objects," Joseph Hennawi, who leads the team from the Max Planck Institute, said in the statement. "The discovery of these young objects challenges the existing theories of black hole formation and will require new models to better understand how black holes and galaxies formed." This is not the first time astronomers have spotted objects that defy conventional understanding.  In recent years, astronomers have spotted several supermassive black holes that formed less than a billion years after the Big Bang. In March, researchers from the Los Alamos National Laboratory in New Mexico used computer simulations to calculate the rate of evolution of supermassive black holes if their growth is fed by cold and dense accretion streams. The simulated black holes created by the researchers were also seen to be interacting with galaxies in the same way that is observed in nature, mimicking star formation rates, galaxy density profiles, and thermal and ionization rates of gases. The next step would be to look for other ancient quasars that are also more massive than they should be. If more such objects are detected, it would not just help scientists create a better model of how the first supermassive black holes in the universe came to be, but also help understand how the one in the Milky Way’s heart formed and evolved. “We would like to find more of these young quasars,” Eilers said. “While finding these three unusual quasars might have been a fluke, finding additional examples would imply that a significant fraction of the known quasar population is much younger than expected.”


Artists' impression of the gas and dust disk around the planet-like object OTS44. First radio observations indicate that OTS44 has formed in the same way as a young star. Credit: Johan Olofsson (U Valparaiso & MPIA) First radio observations of the lonely, planet-like object OTS44 reveal a dusty protoplanetary disk that is very similar to disks around young stars. This is unexpected, given that models of star and planet formation predict that formation from a collapsing cloud, forming a central object with surrounding disk, should not be possible for such low-mass objects. Apparently, stars and planet-like objects are more similar than previously thought. The finding, by an international team led by Amelia Bayo and including several astronomers from the Max Planck Institute for Astronomy, has been published in Astrophysical Journal Letters. A new study of the lonely, planet-like object OTS44 has provided evidence that this object has formed in a similar way as ordinary stars and brown dwarfs – a surprising result that challenges current models of star and planet formation. The study by a group of astronomers, led by Amelia Bayo of the University of Valparaiso and involving several astronomers from the Max Planck Institute for Astronomy, used the ALMA observatory in Chile to detect dust from the disk surrounding OTS44. This detection yielded mass estimates for the dust contained in the disk, which place OTS44 in a row with stars and brown dwarfs (that is, failed stars with too little mass for sustained nuclear fusion): All these objects, it seems, have rather similar properties, including a similar ratio between the mass of dust in the disk and the mass of the central object. The findings supplement earlier research that found OTS44 is still growing by drawing matter from its disk onto itself – another tell-tale similarity between the object and young stars. Taken together, this is compelling evidence that OTS44 formed in the same way as stars and brown dwarfs, namely by the collapse of a cloud of gas and dust. But going by current models of star and planet formation, it should not be possible for an object as low-mass as OTS44 to form in this way. An alternative way, the formation of multiple objects in one go, with low-mass objects like OTS44 among them, is contradicted by the observations, which show no such companion objects anywhere near OTS44. The strength of the radiation received from the dust at millimetre wavelength also suggests the presence of large, millimetre sized dust grains. This, too, is surprising. Under the conditions in the disk of a low-mass object, dust is not expected to clump together to reach this size (or beyond). Instead, the OTS44 dust grains appear to be growing – and might even be on the way of forming a mini-moon around the object; another similarity with stars and their planetary systems. Amelia Bayo (University of Valparaiso), who led this research effort, says: "The more we know about OTS44, the greater its similarities with a young star. But its mass is so low that theory tells us it cannot have formed like a star!" Thomas Henning of the Max Planck Institute for Astronomy adds: "It is amazing how an observatory like ALMA allows us to see half an Earth mass worth of dust orbiting an object with ten times the mass of Jupiter at a distance of 500 light-years. But the new data also shows the limit of our understanding. Clearly, there is still a lot to learn about the formation of low-mass astronomical objects!" Explore further: Brown dwarfs, stars share formation process, new study indicates More information: Amelia Bayo et al. First Millimeter Detection of the Disk around a Young, Isolated, Planetary-mass Object, The Astrophysical Journal (2017). DOI: 10.3847/2041-8213/aa7046


Now, a team of astronomers, including UC Santa Barbara physicist Joseph Hennawi, have made the first measurements of small-scale ripples in this primeval hydrogen gas using rare double quasars. Although the regions of cosmic web they studied lie nearly 11 billion light years away, they were able to measure variations in its structure on scales 100,000 times smaller, comparable to the size of a single galaxy. The results appear in the journal Science. Intergalactic gas is so tenuous that it emits no light of its own. Instead astronomers study it indirectly by observing how it selectively absorbs the light coming from faraway sources known as quasars. Quasars constitute a brief hyperluminous phase of the galactic life cycle powered by matter falling into a galaxy's central supermassive black hole. Acting like cosmic lighthouses, they are bright, distant beacons that allow astronomers to study intergalactic atoms residing between the location of the quasar and the Earth. But because these hyperluminous episodes last only a tiny fraction of a galaxy's lifetime, quasars are correspondingly rare and are typically separated from each other by hundreds of millions of light years. In order to probe the cosmic web on much smaller length scales, the astronomers exploited a fortuitous cosmic coincidence: They identified exceedingly rare pairs of quasars and measured subtle differences in the absorption of intergalactic atoms along the two sightlines. "Pairs of quasars are like needles in a haystack," explained Hennawi, associate professor in UCSB's Department of Physics. Hennawi pioneered the application of algorithms from "machine learning"—a brand of artificial intelligence—to efficiently locate quasar pairs in the massive amounts of data produced by digital imaging surveys of the night sky. "In order to find them, we combed through images of billions of celestial objects millions of times fainter than what the naked eye can see." Once identified, the quasar pairs were observed with the largest telescopes in the world, including the 10-meter Keck telescopes at the W.M. Keck Observatory on Mauna Kea, Hawaii, of which the University of California is a founding partner. "One of the biggest challenges was developing the mathematical and statistical tools to quantify the tiny differences we measured in this new kind of data," said lead author Alberto Rorai, Hennawi's former Ph.D. student who is now a postdoctoral researcher at Cambridge University. Rorai developed these tools as part of the research for his doctoral degree and applied them to spectra of quasars with Hennawi and other colleagues. The astronomers compared their measurements to supercomputer models that simulate the formation of cosmic structures from the Big Bang to the present. On a single laptop, these complex calculations would require almost 1,000 years to complete, but modern supercomputers enabled the researchers to carry them out in just a few weeks. "The input to our simulations are the laws of physics and the output is an artificial universe, which can be directly compared to astronomical data," said co-author Jose Oñorbe, a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany, who led the supercomputer simulation effort. "I was delighted to see that these new measurements agree with the well-established paradigm for how cosmic structures form." "One reason why these small-scale fluctuations are so interesting is that they encode information about the temperature of gas in the cosmic web just a few billion years after the Big Bang," explained Hennawi. Astronomers believe that the matter in the universe went through phase transitions billions of years ago, which dramatically changed its temperature. Known as cosmic re-ionization, these transitions occurred when the collective ultraviolet glow of all stars and quasars in the universe became intense enough to strip electrons off atoms in intergalactic space. How and when re-ionization occurred is one of the biggest open questions in the field of cosmology, and these new measurements provide important clues that will help narrate this chapter of cosmic history. Explore further: Discovery nearly doubles known quasars from the ancient universe More information: "Measurement of the small-scale structure of the intergalactic medium using close quasar pairs" Science, science.sciencemag.org/cgi/doi/10.1126/science.aaf9346


News Article | April 11, 2017
Site: www.techtimes.com

The detection of atmosphere for the first time around an exoplanet named GJ 1132b has excited the scientific world about the prospect of finding evidence of life outside the solar system. The exoplanet orbits a dwarf star GJ 1132 that is some 39 light-years away from Earth. Researchers say the Earth-like planet has a thick, watery atmosphere which exacerbates the scope for finding aliens and other forms of life. The new study published in the Astronomical journal said that GJ 1132b has a radius 1.4 times than that of Earth and in mass exceeds 1.6 times. Unlike the planets in our solar system, it orbits a star that is dimmer than the sun. The presence of the atmosphere has brightened the scope for the existence of life, but it remains to be confirmed. The discovery of atmosphere in the super-Earth exoplanet is a landmark in the hunt for extraterrestrial life. "While this is not the detection of life on another planet, it's an important step in the right direction: The detection of an atmosphere around the super-Earth GJ 1132b marks the first time that an atmosphere has been detected around an Earth-like planet other than Earth itself," said John Southworth, a researcher at Keele University in the UK and first author. However, life-forms are unlikely to survive on this hot world despite the presence of an atmosphere, as the surface temperature of GJ 1132b is around 370 degrees Celsius. According to John Southworth, the hottest temperature at which life could survive on Earth is at 120 degrees Celsius. The presence of life on other planets is probed by scientists by examining the chemical composition of the atmosphere to know the imbalances triggered by living organisms. Earth offers signs of life from the abundance of oxygen. According to Southworth, there is still a long way to go in detecting life on exoplanets. However, he is upbeat that the discovery of atmosphere is a milestone. To confirm the presence of life on the planet, chemical signatures in the celestial bodies are studied — especially the molecules in the planet's atmosphere where light is absorbed in varied ways. The new planet was found to be having a thick atmosphere which may be containing steam, methane, or a combination of both. There is a high probability the planet may be a 'water world' with the atmosphere containing hot steam. The planet GJ 1132b was discovered in 2015 and dubbed as a potential twin of Venus considering the similarity of a rocky world and high temperature at the surface. Spotted in the Vela constellation, the detection of GJ 1132b was enabled by the 2.2-m ESO/MPG telescope of the European Southern Observatory in Chile, where researchers noted variations in brightness as the planet and atmosphere were absorbing starlight when passing before the host star. The research team had scientists from the Max Planck Institute for Astronomy. Commenting on the research, Marek Kukula the public astronomer at the Royal Observatory Greenwich called it a good proof of concept. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


Carilli C.L.,U.S. National Radio Astronomy Observatory | Walter F.,Max Planck Institute for Astronomy
Annual Review of Astronomy and Astrophysics | Year: 2013

Over the past decade, observations of the cool interstellar medium (ISM) in distant galaxies via molecular and atomic fine structure line (FSL) emission have gone from a curious look into a few extreme, rare objects to a mainstream tool for studying galaxy formation out to the highest redshifts. Molecular gas has been observed in close to 200 galaxies at z > 1, including numerous AGN host-galaxies out to z ∼ 7, highly star-forming submillimeter galaxies, and increasing samples of main-sequence color-selected star-forming galaxies at z ∼ 1.5 to 2.5. Studies have moved well beyond simple detections to dynamical imaging at kiloparsec-scale resolution and multiline, multispecies studies that determine the physical conditions in the ISM in early galaxies. Observations of the cool gas are the required complement to studies of the stellar density and star-formation history of the Universe as they reveal the phase of the ISM that immediately precedes star formation in galaxies. Current observations suggest that the order of magnitude increase in the cosmic star-formation rate density from z ∼ 0 to 2 is commensurate with a similar increase in the gas-to-stellar mass ratio in star-forming disk galaxies. Progress has been made in determining the CO luminosity to H2 mass conversion factor at high z, and the dichotomy between high versus low values for main-sequence versus starburst galaxies, respectively, appears to persist with increasing redshift, with a likely dependence on metallicity and other local physical conditions. There may also be two sequences in the relationship between star-formation rate and gas mass: one for starbursts, in which the gas consumption timescale is short (a few 107 years), and one for main sequence galaxies, with an order of magnitude longer gas consumption timescale. Studies of atomic FSL emission are rapidly progressing, with some tens of galaxies detected in the exceptionally bright [Cii] 158-μm line to date. The [Cii] line is proving to be a unique tracer of galaxy dynamics in the early Universe and, together with other atomic FSLs, has the potential to be the most direct means of obtaining spectroscopic redshifts for the first galaxies during cosmic reionization. Copyright ©2013 by Annual Reviews. All rights reserved.


Henning T.,Max Planck Institute for Astronomy | Semenov D.,Max Planck Institute for Astronomy
Chemical Reviews | Year: 2013

The wide range of planetary system architectures and exoplanet properties is certainly linked to a range of properties of their birth-places, the disk-like structures around young stars composed of gas and dust particles. These disks share many of the properties of the solar nebula from which the Sun and our planetary system formed, although their masses, radial dimensions, and internal structures can be very different. Dust spectroscopy has revealed the mineralogical composition of the protoplanetary dust particles that are mostly found in the form of amorphous silicates, crystalline forsterite, water ice, and other molecular ices. There is strong observational evidence that the dust particles in disks can grow in size far beyond the typical sub-micrometer sizes of interstellar dust grains.


Henning T.,Max Planck Institute for Astronomy
Annual Review of Astronomy and Astrophysics | Year: 2010

Silicate dust particles are an important player in the cosmic life cycle of matter. They have been detected in a wide variety of environments, ranging from nearby protoplanetary disks to distant quasars.This review summarizes the fundamental properties of silicates relevant to astronomical observations and processes. It provides a review of our knowledge about cosmic silicates, mostly based on results from IR spectroscopy. © 2010 by Annual Reviews.


Dullemond C.P.,Max Planck Institute for Astronomy | Monnier J.D.,University of Michigan
Annual Review of Astronomy and Astrophysics | Year: 2010

To understand how planetary systems form in the dusty disks around premain-sequence stars, a detailed knowledge of the structure and evolution of these disks is required. Although this is reasonably well understood for the regions of the disk beyond about 1) AU, the structure of these disks inward of 1 AU remains a puzzle. This is partly because it is very difficult to spatially resolve these regions with current telescopes. But it is also because the physics of this region, where the disk becomes so hot that the dust starts to evaporate, is poorly understood. With infrared interferometry it has become possible in recent years to directly spatially resolve the inner 1 AU of protoplanetary disks, albeit in a somewhat limited way. These observations have partly confirmed current models of these regions, but also posed new questions and puzzles. Moreover, it has turned out that the numerical modeling of these regions is extremely challenging. In this review, we give a rough overview of the history and recent developments in this exciting field of astrophysics. © 2010 by Annual Reviews.


Mordasini C.,Max Planck Institute for Astronomy
Astronomy and Astrophysics | Year: 2013

Context. The intrinsic luminosity of young Jupiters is of high interest for planet formation theory. It is an observable quantity that is determined by important physical mechanisms during formation, namely, the structure of the accretion shock and, even more fundamentally, the basic formation mechanism (core accretion or gravitational instability). Aims. Our aim is to study the impact of the core mass on the post-formation entropy and luminosity of young giant planets forming via core accretion with a supercritical accretion shock that radiates all accretion shock energy (cold accretion). Methods. For this, we conduct self-consistently coupled formation and evolution calculations of giant planets with masses between 1 and 12 Jovian masses and core masses between 20 and 120 Earth masses in the 1D spherically symmetric approximation. Results. As the main result, it is found that the post-formation luminosity of massive giant planets is very sensitive to the core mass. An increase in the core mass by a factor 6 results in an increase in the post-formation luminosity of a 10-Jovian mass planet by a factor 120, indicating a dependency as \hbox{$\mcore^{2- 3}$}. Due to this dependency, there is no single well-defined post-formation luminosity for core accretion, but a wide range, even for completely cold accretion. For massive cores (~100 Earth masses), the post-formation luminosities of core accretion planets become so high that they approach those in the hot start scenario that is often associated with gravitational instability. For the mechanism to work, it is necessary that the solids are accreted before or during gas runaway accretion and that they sink during this time deep into the planet. Conclusions. We make no claims about whether such massive cores can actually form in giant planets especially at large orbital distances. But if they can form, it becomes difficult to rule out core accretion as the formation mechanism based solely on luminosity for directly imaged planets that are more luminous than predicted for low core masses. Instead of invoking gravitational instability as the consequently necessary formation mode, the high luminosity can also be caused, at least in principle, simply by a more massive core. © 2013 ESO.

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