The Max Planck Institute for Extraterrestrial Physics is a Max Planck Institute, located in Garching, near Munich, Germany.In 1991 the Max Planck Institute for Physics and Astrophysics split up into the Max Planck Institute for Extraterrestrial Physics, the Max Planck Institute for Physics and the Max Planck Institute for Astrophysics. The Max Planck Institute for Extraterrestrial Physics was founded as sub-institute in 1963. Thescientific activities of the institute are mostly devoted to astrophysics with telescopes orbiting in space. A large amount of the resourcesare spent for studying black holes in the galaxy and in the remote universe. Wikipedia.
News Article | April 17, 2017
New observations using ESO’s Very Large Telescope (VLT) in Chile indicate that massive, star-forming galaxies in the early universe were dominated by normal, baryonic matter. This is in stark contrast to present-day galaxies, where the effects of dark matter on the rotational velocity of spiral galaxies seem to be much greater. The surprising result, published in Nature by an international team of astronomers led by Reinhard Genzel at the Max Planck Institute for Extraterrestrial Physics in Germany, suggests that dark matter was less influential in the early universe than it is today. Whereas normal matter in the cosmos can be viewed as brightly shining stars, glowing gas and clouds of dust, dark matter does not emit, absorb or reflect light. This elusive, transparent matter can only be observed via its gravitational effects, one of which is a higher speed of rotation in the outer parts of spiral galaxies. The disc of a spiral galaxy rotates with a velocity of hundreds of kilometres per second, making a full revolution in a period of hundreds of millions of years. If a galaxy’s mass consisted entirely of normal matter, the sparser outer regions should rotate more slowly than the dense regions at the centre. But observations of nearby spiral galaxies show that their inner and outer parts actually rotate at approximately the same speed. It is widely accepted that the observed “flat rotation curves” indicate that spiral galaxies contain large amounts of non-luminous matter in a halo surrounding the galactic disc. This traditional view is based on observations of numerous galaxies in the local universe, but is now challenged by the latest observations of galaxies in the distant universe. The rotation curve of six massive, star-forming galaxies at the peak of galaxy formation, 10 billion years ago, was measured with the KMOS and SINFONI instruments on the VLT, and the results are intriguing. Unlike local spiral galaxies, the outer regions of these distant galaxies seem to be rotating more slowly than regions closer to the core – suggesting they contain less dark matter than expected. The same decreasing velocity trend away from the centres of the galaxies is also found in a composite rotation curve that combines data from around 100 other distant galaxies, which have too weak a signal for an individual analysis. Genzel and collaborators identify two probable causes for the unexpected result. Besides a stronger dominance of normal matter with the dark matter playing a much smaller role, they also suggest that early disc galaxies were much more turbulent than the spiral galaxies we see in our cosmic neighbourhood. Both effects seem to become more marked as astronomers look further back in time into the early universe. This suggests that three to four billion years after the Big Bang, the gas in galaxies had already efficiently condensed into flat, rotating discs, while the dark-matter halos surrounding them were much larger and more spread out. Apparently it took billions of years longer for dark matter to condense as well, so its dominating effect is only seen on the rotation velocities of galaxy discs today. This explanation is consistent with observations showing that early galaxies were much more gas-rich and compact than today’s galaxies. Embedded in a wider dark-matter halo, their rotation curves would be only weakly influenced by its gravity. It would be therefore interesting to explore whether the suggestion of a slow condensation of dark-matter halos could help shed light on this mysterious component of the universe.
News Article | April 17, 2017
The birthplace of black holes is to be found in the peaceful village of Thornhill in the English county of Yorkshire. In the 18th century, this is where John Michell made his home, next to the medieval church. He was the rector here for 26 years and – as borne out by the inscription on his memorial in the church – highly respected as a scholar as well. In fact, Michell had studied not only theology, Hebrew and Greek at Cambridge, but had also turned his attention to the natural sciences. His main interest was geology. In one treatise, which was published after the Lisbon earthquake of 1755, he claimed that subterranean waves existed which propagated such an earthquake. This theory caused quite a stir in the academic world, and led to John Michell being accepted as a Fellow of the Royal Society in London, not least because of this theory. He gave a talk before this renowned society in 1783 on the gravitation of stars. He used a thought experiment to explain that light would not leave the surface of a very massive star if the gravitation was sufficiently large. And he deduced: "Should such an object really exist in nature, its light could never reach us." More than a decade after Michell, another scientist took up this same topic: in his book published in 1796 - Exposition du Système du Monde - the French mathematician, physicist and astronomer Pierre-Simon de Laplace described the idea of massive stars from which no light could escape; this light consisted of corpuscles, very small particles, according to the generally accepted theory of Isaac Newton. Laplace called such an object corps obscur, i.e. dark body. The physical thought games played by John Michell and Pierre-Simon de Laplace did not meet with much response, however, and were quickly forgotten. It was left to Albert Einstein with his General Theory of Relativity to pave the way for these "dark bodies" to enter the realms of science – without this really being his intention. Although the existence of point singularities, in which matter and radiation from our world would simply disappear, can be derived from the equations he published in 1915, 1939 saw Einstein publish an article in the journal Annals of Mathematics in which he intended to prove that such black holes were impossible. But back in 1916, the astronomer Karl Schwarzschild had taken the Theory of General Relativity as his basis to calculate the size and the behaviour of a non-rotating static black hole carrying no electric charge. His name has been given to the mass-dependent radius of such an object, inside which nothing can escape to the outside. This radius would be around one centimetre for Earth. Schwarzschild had a meteoric career during his short life. Born in 1873 as the eldest of six children of a German-Jewish family in Frankfurt, his talent emerged at an early age. He was only 16 when he published two papers in a renowned journal on the determination of the orbits of planets and binary stars. His subsequent career in astronomy took him via Munich, Vienna and Göttingen to Potsdam, where he became director of the astrophysical observatory in 1909. A few years later, in the middle of Word War I – Karl Schwarzschild was artillery second lieutenant on the Eastern front in Russia – he derived the exact solutions for Einstein's field equations. He died on 11 May 1916 from an auto-immune disease of the skin. The topic of black holes did not yet find its way into the scientific domain, however. If anything, the interest in Einstein's theoretical construct diminished more and more after the initial hype. This phase lasted approximately from the mid-1920s to the middle of the 1950s. Then followed what the physicist Clifford Will called the "renaissance" of the General Theory of Relativity. It now became important to describe objects which initially were only of interest to the theoreticians. White dwarves, for example, or neutron stars where matter exists in very extreme states. Their unexpected properties could be explained with the aid of new concepts derived from this theory. So the black holes moved into the focus of attention as well. And scientists working on them became stars – like the British physicist Stephen Hawking. At the beginning of the 1970s, Uhuru heralded in a new era for observational astronomy. The satellite surveyed the universe in the range of extremely short wavelength X-ray radiation. Uhuru discovered hundreds of sources, usually neutron stars. But among them was one particular object in the Cygnus (=swan) constellation. It was given the designation Cygnus X-1. Researchers discovered it to be a giant star of around 30 solar masses which shone with a blue glow. An invisible object of around 15 solar masses orbits around it – apparently a black hole. This also explains the X-rays recorded: the gravity of the black hole attracts the matter of the main star. This collects in a so-called accretion disk around the massive monster, swirls around it at incredibly high speed, is heated up to several million degrees by the friction – and emits X-rays before it disappears in the space-time chasm. Cygnus X-1 is by no means the only black hole which the astronomers have detected indirectly. So far, they have found a whole series of them with between 4 and 16 solar masses. But there is one which is much more massive. It is located at the heart of our Milky Way, around 26,000 light years away, and was discovered at the end of the 1990s. In 2002, a group including Reinhard Genzel from the Max Planck Institute for Extraterrestrial Physics succeeded in making a sensational discovery: at the Very Large Telescope of the European Southern Observatory (ESO), the scientists observed a star which had approached the galactic centre to within a mere 17 light hours (just over 18 billion kilometres). During the months and years that followed, they were able to observe the orbital motion of this star, which was given the designation S2. It orbits the centre of the galaxy (Sagittarius A*) once every 15.2 years at a speed of 5000 kilometres per second. From the motion of S2 and other stars, the astronomers concluded that around 4.5 million solar masses are concentrated in a region the size of our planetary system. There is only one plausible explanation for such a density: a gigantic black hole. Our Milky Way is no exception: the scientists believe that these mass monsters lurk at the centres of most galaxies – some even much larger than Sagittarius A*. A black hole of approx. 6.6 billion solar masses is located inside a giant galaxy known as M87! Like Sagittarius A*, this stellar system 53 million light years away is also part of the observation programme of the Event Horizon Telescope. With the discovery of gravitational waves in September 2015, the history of black holes reached its present climax. At that time, waves from two merging holes with 36 and 29 solar masses were registered. This heralded in a new era of astronomy, whose aim is to bring light into the dark universe. And also to shed light on these mysterious black holes. Explore further: Astronomers hoping to directly capture image of a black hole
News Article | April 17, 2017
Darkness gathers – but it can take time. About 10 billion years ago, massive star-forming galaxies were dominated by normal matter, not the dark matter that’s so influential in galaxies today. If spiral galaxies were only made up of the matter that we can see, stars at the outer edge should orbit the centre slower than those closer in. But in the 1970s, American astronomers Vera Rubin and Kent Ford noticed that this was not the case: all the stars in the Andromeda galaxy move at similar speeds, regardless of their distance from the galactic center. This study constituted some of the first evidence for dark matter, matter that doesn’t interact with light and which we can only observe via its gravitational effects. If a galactic disc sat in a pervasive dark matter “halo”, that extra unseen mass could explain the stars’ unexpected motion. In order to figure out how today’s galaxies came to be so full of dark matter, we have to look to their predecessors, the star-forming galaxies of the early universe. But learning about dark matter in galaxies in the early universe is difficult: because we cannot see dark matter, we must carefully observe the movements of extraordinarily distant stars. Now, Natascha Förster Schreiber at the Max Planck Institute for Extraterrestrial Physics in Germany and her colleagues have used the Very Large Telescope in Chile to make the most detailed observations yet of the movement of six massive galactic discs during the peak era of galaxy formation, 10 billion years ago. They found that, unlike in most modern galaxies, the stars at the edges of these early galaxies move more slowly than those closer in. “This tells us that at early stages of galaxy formation, the relative distribution of the normal matter and the dark matter was significantly different from what it is today,” says Förster Schreiber. In order to check their unexpected results, the researchers used a “stack” of 100 images of other early galaxies to find an average picture of their rotations. The stacked galaxies matched the rotations of the more rigorously studied ones. “We’re not just looking at six weirdo galaxies – this could be more common,” says Förster Schreiber. “For me, that was the wow moment.” The differences in early galaxies’ rotations demonstrates that there is very little dark matter in towards their middle. Instead, they are almost entirely made up of the matter we can see in the form of stars and gas. The further away (and thus earlier in cosmic history) the galaxies were, the less dark matter they contained. This result suggests that the turbulent gas in early galaxies condensed into the flat, rotating disc shapes we see today more quickly than dark matter, which remained in a diffuse halo around galaxies for longer. “This is an important step in trying to figure out how galaxies like the Milky Way and larger galaxies must have assembled,” says Mark Swinbank at Durham University. “Having a constraint on how early the gas and stars must have formed the discs and how well-mixed they were with dark matter is important to informing their evolution.”
News Article | April 19, 2017
New data from NASA's Chandra X-ray Observatory and other telescopes has revealed details about this giant black hole, located some 145 million light years from Earth. Although the black hole itself is undetected, astronomers are learning about the impact it has on the galaxy it inhabits and the larger cluster around it. In some ways, this black hole resembles a beating heart that pumps blood outward into the body via the arteries. Likewise, a black hole can inject material and energy into its host galaxy and beyond. By examining the details of the X-ray data from Chandra, scientists have found evidence for repeated bursts of energetic particles in jets generated by the supermassive black hole at the center of NGC 4696. These bursts create vast cavities in the hot gas that fills the space between the galaxies in the cluster. The bursts also create shock waves, akin to sonic booms produced by high-speed airplanes, which travel tens of thousands of light years across the cluster. This composite image contains X-ray data from Chandra (red) that reveals the hot gas in the cluster, and radio data from the NSF's Karl G. Jansky Very Large Array (blue) that shows high-energy particles produced by the black hole-powered jets. Visible light data from the Hubble Space Telescope (green) show galaxies in the cluster as well as galaxies and stars outside the cluster. Astronomers employed special processing to the X-ray data (shown above) to emphasize nine cavities visible in the hot gas. These cavities are labeled A through I in an additional image, and the location of the black hole is labeled with a cross. The cavities that formed most recently are located nearest to the black hole, in particular the ones labeled A and B. The researchers estimate that these black hole bursts, or "beats", have occurred every five to ten million years. Besides the vastly differing time scales, these beats also differ from typical human heartbeats in not occurring at particularly regular intervals. A different type of processing of the X-ray data (shown above) reveals a sequence of curved and approximately equally spaced features in the hot gas. These may be caused by sound waves generated by the black hole's repeated bursts. In a galaxy cluster, the hot gas that fills the cluster enables sound waves—albeit at frequencies far too low for the human hear to detect—to propagate. (Note that both images showing the labeled cavities and this image are rotated slightly clockwise to the main composite.) The features in the Centaurus Cluster are similar to the ripples seen in the Perseus cluster of galaxies. The pitch of the sound in Centaurus is extremely deep, corresponding to a discordant sound about 56 octaves below the notes near middle C. This corresponds to a slightly higher (by about one octave) pitch than the sound in Perseus. Alternative explanations for these curved features include the effects of turbulence or magnetic fields. The black hole bursts also appear to have lifted up gas that has been enriched in elements generated in supernova explosions. The authors of the study of the Centaurus cluster created a map showing the density of elements heavier than hydrogen and helium. The brighter colors in the map show regions with the highest density of heavy elements and the darker colors show regions with a lower density of heavy elements. Therefore, regions with the highest density of heavy elements are located to the right of the black hole. A lower density of heavy elements near the black hole is consistent with the idea that enriched gas has been lifted out of the cluster's center by bursting activity associated with the black hole. The energy produced by the black hole is also able to prevent the huge reservoir of hot gas from cooling. This has prevented large numbers of stars from forming in the gas. A paper describing these results was published in the March 21st 2016 issue of the Monthly Notices of the Royal Astronomical Society and is available online. The first author is Jeremy Sanders from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. More information: J. S. Sanders et al. A very deepview of metals, sloshing and feedback in the Centaurus cluster of galaxies, Monthly Notices of the Royal Astronomical Society (2016). DOI: 10.1093/mnras/stv2972 , https://arxiv.org/abs/1601.01489
Davies R.,Max Planck Institute for Extraterrestrial Physics |
Kasper M.,European Southern Observatory
Annual Review of Astronomy and Astrophysics | Year: 2012
Adaptive optics is a prime example of how progress in observational astronomy can be driven by technological developments. At many observatories it is now considered to be part of a standard instrumentation suite, enabling ground-based telescopes to reach the diffraction limit and, thus, providing spatial resolution erior to that achievable from space with current or planned satellites. In this review, we consider adaptive optics from the astrophysical perspective. We show that adaptive optics has led to important advances in our understanding of a multitude of astrophysical processes and describe how the requirements from science applications are now driving the development of the next generation of novel adaptive optics techniques. Copyright © 2012 by Annual Reviews.
Genzel R.,Max Planck Institute for Extraterrestrial Physics |
Eisenhauer F.,Max Planck Institute for Extraterrestrial Physics |
Gillessen S.,Max Planck Institute for Extraterrestrial Physics
Reviews of Modern Physics | Year: 2010
The Galactic Center is an excellent laboratory for studying phenomena and physical processes that may be occurring in many other galactic nuclei. The center of our Milky Way is by far the closest galactic nucleus, and observations with exquisite resolution and sensitivity cover 18 orders of magnitude in energy of electromagnetic radiation. Theoretical simulations have become increasingly more powerful in explaining these measurements. This review summarizes the recent progress in observational and theoretical work on the central parsec, with a strong emphasis on the current empirical evidence for a central massive black hole and on the processes in the surrounding dense nuclear star cluster. Current evidence is presented, from the analysis of the orbits of more than two dozen stars and from the measurements of the size and motion of the central compact radio source, Sgr A*, that this radio source must be a massive black hole of about 4.4× 106 Ma, beyond any reasonable doubt. What is known about the structure and evolution of the dense nuclear star cluster surrounding this black hole is reported, including the astounding fact that stars have been forming in the vicinity of Sgr A* recently, apparently with a top-heavy stellar-mass function. A dense concentration of fainter stars centered in the immediate vicinity of the massive black hole are discussed, three of which have orbital peri-bothroi of less than one light day. This "S-star cluster" appears to consist mainly of young early-type stars, in contrast to the predicted properties of an equilibrium "stellar cusp" around a black hole. This constitutes a remarkable and presently not fully understood "paradox of youth." What is known about the emission properties of the accreting gas onto Sgr A* is also summarized and how this emission is beginning to delineate the physical properties in the hot accretion zone around the event horizon. © 2011 American Physical Society.
Lutz D.,Max Planck Institute for Extraterrestrial Physics
Annual Review of Astronomy and Astrophysics | Year: 2014
Roughly half of the radiation from evolving galaxies in the early Universe reaches us in the far-infrared and submillimeter wavelength ranges. Recent major advances in observing capabilities, in particular the launch of the Herschel Space Observatory in 2009, have dramatically enhanced our ability to use this information in the context of multiwavelength studies of galaxy evolution. Near its peak, three-quarters of the cosmic infrared background is now resolved into individually detected sources. The use of far-infrared diagnostics of dust-obscured star formation and of interstellar medium conditions has expanded from extreme and rare extreme high-redshift galaxies to more typical main-sequence galaxies and hosts of active galactic nuclei out to z≳2. These studies shed light on the evolving role of steady equilibrium processes and of brief starbursts at and since the peak of cosmic star formation and black hole accretion. This review presents a selection of recent far-infrared studies of galaxy evolution with an emphasis on Herschel results. Copyright © 2014 by Annual Reviews.
van Eerten H.,Max Planck Institute for Extraterrestrial Physics
Monthly Notices of the Royal Astronomical Society | Year: 2014
A sufficiently powerful astrophysical source with power-law luminosity in time will give rise to a self-similar relativistic blast wave with a reverse shock travelling into the ejecta and a forward shock moving into the surrounding medium. Once energy injection ceases and the last energy is delivered to the shock front, the blast wave will transit into another self-similar stage depending only on the total amount of energy injected. I describe the effect of limited duration energy injection into environments with density depending on radius as a power law, emphasizing optical/X-ray Gamma-ray Burst afterglows as applications. The blast wave during injection is treated analytically, the transition following last energy injection with one-dimensional simulations. Flux equations for synchrotron emission from the forward and reverse shock regions are provided. The reverse shock emission can easily dominate, especially with different magnetizations for both regions. Reverse shock emission is shown to support both the reported X-ray and optical correlations between afterglow plateau duration and end time flux, independently of the luminosity power-law slope. The model is demonstrated by application to bursts 120521A and 090515, and can accommodate their steep post-plateau light-curve slopes. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Diehl R.,Max Planck Institute for Extraterrestrial Physics
Reports on Progress in Physics | Year: 2013
Measurements of high-energy photons from cosmic sources of nuclear radiation through ESA's INTEGRAL mission have advanced our knowledge: new data with high spectral resolution showed that characteristic gamma-ray lines from radioactive decays occur throughout the Galaxy in its interstellar medium. Although the number of detected sources and often the significance of the astrophysical results remain modest, conclusions derived from this unique astronomical window of radiation originating from nuclear processes are important, complementing the widely-employed atomic-line based spectroscopy. We review the results and insights obtained in the past decade from gamma-ray line measurements of cosmic sources in the context of their astrophysical questions. © 2013 IOP Publishing Ltd.
Dennerl K.,Max Planck Institute for Extraterrestrial Physics
Space Science Reviews | Year: 2010
Charge transfer, or charge exchange, describes a process in which an ion takes one or more electrons from another atom. Investigations of this fundamental process have accompanied atomic physics from its very beginning, and have been extended to astrophysical scenarios already many decades ago. Yet one important aspect of this process, i.e. its high efficiency in generating X-rays, was only revealed in 1996, when comets were discovered as a new class of X-ray sources. This finding has opened up an entirely new field of X-ray studies, with great impact due to the richness of the underlying atomic physics, as the X-rays are not generated by hot electrons, but by ions picking up electrons from cold gas. While comets still represent the best astrophysical laboratory for investigating the physics of charge transfer, various studies have already spotted a variety of other astrophysical locations, within and beyond our solar system, where X-rays may be generated by this process. They range from planetary atmospheres, the heliosphere, the interstellar medium and stars to galaxies and clusters of galaxies, where charge transfer may even be observationally linked to dark matter. This review attempts to put the various aspects of the study of charge transfer reactions into a broader historical context, with special emphasis on X-ray astrophysics, where the discovery of cometary X-ray emission may have stimulated a novel look at our universe. © 2010 The Author(s).