Research Contributions to the Yearbook of the Max Planck Society
(Full contributions are in German)
Testing Einstein's Most Fortunate Thought
Freire, Paulo; Kramer, Michael
Extremely precise measurements of the motion of a fast-spinning pulsar in a triple star system provide one of the strongest tests ever of a simple, but fundamental prediction of general relativity: that gravity affects all objects with the same acceleration, without regard for their composition, density or the strength of their own gravitational field. General relativity has again survived this test, one of the most stringent ever, which strongly constrains many alternative theories of gravity.
Extremely precise measurements of the motion of a fast-spinning pulsar in a triple star system provide one of the strongest tests ever of a simple, but fundamental prediction of general relativity: that gravity affects all objects with the same acceleration, without regard for their composition, density or the strength of their own gravitational field. General relativity has again survived this test, one of the most stringent ever, which strongly constrains many alternative theories of gravity.
The first image of the shadow of a black hole
Zensus, J. Anton; Kramer, Michael; Menten, Karl M.; Britzen, Silke (2019)
On April 10, 2019, the first image of a black hole was published by a team of 347 international scientists from 59 institutes in 18 countries. Theoretical work and indirect evidence for the existence of black holes has been around for a long time. Only now did the observations provide the necessary resolution for an image made possible by a combination of seven radio telescopes scattered across the Earth, observing the centre of the galaxy M87. More than 30 scientists and engineers of the Max Planck Institute for Radio Astronomy in Bonn are involved in this success.
The airborne observatory SOFIA reveals gas kinematics in the Lagoon nebula
Wyrowski, F.; Wiesemeyer, H.; Tiwari, M.; Klein, B.; Menten, K.M. (2018)
The airborne observatory SOFIA allows astronomical observations in the Far-Infrared, which is not accessible from the ground. It covers the most important cooling lines of the interstellar medium. Velocity-resolved observations of these lines are crucial for our understanding of the star formation process. Here we present observations of the ionized carbon finestructure line in the Lagoon Nebula, which for the first time reveals the gas motions in the immediate environment of the nebula.
Zooming into the heart of a radio galaxy
Boccardi, Bia (2017)
The formation of relativistic jets in active galaxies is a poorly understood physical process. Providing observational constraints for theoretical models is a crucial but challenging task, since it requires the imaging of emission regions in the immediate proximity of the black hole. We have observed the prototype radio galaxy Cygnus A through very-long-baseline interferometry at millimeter wavelengths, and obtained a sharp view of the jet base. Our analysis of the jet kinematic properties and internal structure suggests that the jet of Cygnus A is a disk wind accelerated by magnetic fields.
Radio bursts from deep space
Spitler, Laura (2016)
For the last 10 years radio astronomers have been detecting short-duration, strong bursts of radio waves from unknown astronomical sources outside our own Galaxy. The discovery of these fast radio bursts (FRBs) sparked a lot of interest, because the estimated distances to the FRBs is 100s of millions to billions of light years. It is an astrophysical puzzle how radio bursts of such intensity can be produced.
Astro-archaeology with the APEX telescope: A historical star collision as novel source of interstellar molecules
Menten, Karl M.; Kamiński, Tomasz (2015)
The APEX telescope in Chile observed the sky position of the oldest historical nova, first discovered in 1670. Very surprisingly, emission from a multitude of different, even organic molecules was detected. Their peculiar isotopologic composition suggests that by no means ”normal” interstellar gas is observed, but rather material that was set free in a collision of two stars. This completely new source of interstellar molecular emission permits investigations of the end products of stellar collisions, a process that possibly occurs much more frequently than previously thought.
Binary Supermassive Black Holes at the Cores of Galaxies
Komossa, S.; Britzen, S. (2015)
Binary supermassive black holes are important for our understanding of the galaxies’ formation and evolution. Coalescing binaries are among the strongest emitters of gravitational waves in the universe. With high-resolution radio observations close pairs of massive black holes can be resolved spatially, providing a direct means of detection. The closest binaries can no longer be spatially resolved, and other methods of detection are in use. Recently, first hints for the influence of a supermassive binary black hole on the lightcurve of an X-ray outburst from a non-active galaxy were found.
The Square Kilometre Array (SKA) − The radio telescope for the next generation
Klöckner, Hans-Rainer (2014)
The Square Kilometre Array will be the most ambitious radio telescope ever planned. The scientific capabilities and its technological challenges will open up new windows of discovery space and will place the SKA as one of the cornerstones in the exploration of the Universe’s most fundamental questions. The upcoming year 2014 will be the most influential one in the SKA design process. Employees from the German SKA working group and the MPS are involved in various design studies in order to create the blueprint of this super science machine of the next 50 years.
Infrared Interferometry of dust and gas disks surrounding young stars
Kreplin, Alexander; Weigelt, Gerd; Grinin, Vladimir; Hofmann, Karl-Heinz; Schertl, Dieter; Tambovtseva, Larisa (2014)
Infrared interferometry with three or more telescopes can provide an angular resolution that is as high as the theoretical resolution of a telescope with a mirror diameter of 130m. It is even possible to perform infrared interferometric measurements with both high angular resolution and high spectral resolution simultaneously. This method enables us to obtain unique insights into the circumstellar disks of young stars and makes studies of the accretion process possible. Measurements of the young stars KK Oph und MWC 297 are presented.
Cradle of the sun
Pfalzner, Susanne (2013)
The Sun formed about 4.6 billion years ago and is located today in a region of a low stellar density. Susanne Pfalzner and her team investigate whether the Sun formed in a similar environment or not. They find several clues that the Sun was born in close proximity of other stars that influenced the nascent planetary system. By combining theory and observation the birth environment of the Solar system can be surprisingly well characterized.
A detailed view of the fast outflows produced by supermassive black holes
Savolainen, Tuomas (2013)
Supermassive black holes can power fast, well-collimated jets of magnetized plasma that transport energy from the black hole – accretion disk system to distances of hundreds of thousands of light years. Many physical processes governing the jets are not well-understood including their formation, stability, magnetic field structure, and energy dissipation. Long-term monitoring of a large sample of active galactic nuclei jets using ultra-high resolution radio interferometry is bringing us closer to the answers to these questions.
Dusty tori in active galactic nuclei
Tristram, Konrad R. W.; Kishimoto, Makoto; Weigelt, Gerd (2012)
Many galaxies host supermassive black holes with masses of millions to billions of solar masses in their centres. The growth of the black holes is fundamental for the evolution of galaxies. A toroidal distribution of gas and dust, the so-called dusty torus, plays a major role as a reservoir of material for the accretion onto the black hole. Only since a few years it is possible to study the compact structures and physical properties of such tori directly using infrared interferometry.
LOFAR - the new software telescope for long radio waves
Beck, Rainer; Verbiest, Joris P. W.; Anderson, James M.; Kramer, Michael (2012)
The new digitally steered meter-wave radio telescope LOFAR (Low Frequency Array), designed by ASTRON/Netherlands, has fibre-connected stations in the Netherlands, Germany, France, Sweden, and the UK. Jointly operated as the International LOFAR Telescope (ILT), it has the world’s largest collecting area. It opens up new possibilities in many astronomical research areas. The MPI for Radio Astronomy investigates the emission of pulsars and to measure magnetic fields in pulsar-wind nebulae, in our Milky Way and in external galaxies.
APEX telescope observations of new molecular ions
Wyrowski, Friedrich; Menten, Karl; Güsten, Rolf; Belloche, Arnaud (2011)
Hydrides are key ingredients of interstellar chemistry since they are the initial products of chemical networks that lead to the formation of more complex molecules. Using the APEX telescope, we observed the long sought hydrides SH+ and OH+ in absorption against the strong continuum source Sagittarius B2(M). The observations show that these hydrides are abundant in diffuse clouds. We used the strongest submillimeter dust continuum sources in the inner galaxy to serve as background to conduct a systematic census of these hydrides in diffuse clouds and massive star forming regions of our galaxy.
Active Galactic Nuclei as high-energy particle accelerators: Probing the physical processes in the vicinity of Black Holes
Fuhrmann, Lars; Zensus, Johann Anton; Angelakis, Emmanouil; Krichbaum, Thomas (2011)
Active galaxies and their innermost core regions show extreme physical processes. In the vicinity of a supermassive black hole they produce an enormous amount of energy output and often also high-energy gamma-ray photons at MeV/GeV energies. Many of the physical processes are so far not understood in detail, e.g. the production of their highly relativistic jets or the origin of the gamma-ray emission as well as the observed variability across the whole electromagnetic spectrum. New instruments and observing programs allow now to obtain new insights into the extreme physics of these objects.
Infrared Interferometry of Active Galactic Nuclei
Hönig, Sebastian; Hofmann, Karlheinz; Kishimoto, Makoto; Tristram, Konrad; Weigelt, Gerd (2010)
With the advancement of Infrared Interferometry it is now possible to directly observe and spatially resolve the dusty tori in active galaxies. These tori provide the dust and gas which is eventually accreted onto the supermassive black hole in the nucleus of the galaxy. It is now possible to study the structure and distribution of the matter in the torus in detail. This may lead to an improved understanding of the growth of supermassive black holes.
Radio pulsars test fundamental physics in space
Kramer, Michael; Wex, Norbert (2010)
Radio pulsars are extremely compact neutron stars. Some of them have a rotational stability that is comparable to the precision of the best atomic clocks. In particular pulsars in binary systems are therefore ideal to test Einstein's general theory of relativity in strong gravitational fields. Changes in the orbital motion of binary pulsars are presently the only firm evidence for the existence of gravitational waves as predicted by general relativity. It is expected that in the next few years pulsars will allow the direct measurement of gravitational waves caused by super massive black holes.
Water in the early Universe
Impellizzeri, C.M. Violette; McKean, John P.; Castangia, Paola; Roy, Alan L.; Henkel, Christian; Brunthaler, Andreas; Wucknitz, Olaf (2009)
Nuclear environments of galaxies are difficult to observe. Dense clouds containing dust inhibit observational access to these interesting regions at optical or ultraviolet wavelengths. Observations in the far infrared or at X-rays do not provide the required angular resolution to map the innermost parts of galaxies hosting supermassive nuclear engines. However, the 1.3-cm line of water vapor, the strongest spectral line at radio wavelengths, is ideal for such studies. The line permits observations under normal weather conditions, helps to detect water in external galaxies, and allows us to map its distribution with submilliarcsecond resolution. As a consequence, nuclear accretion disks can be mapped, their morphology and size can be evaluated, and direct “geometrical” distances of galaxies can be obtained. In the future, this may lead to the determination of the expansion rate of the local Universe with unprecedented accuracy and to new constraints to the equation of state of the dark energy. In the following, we report the detection of water in the early Universe. This result was obtained by a Ph.D. student of the Max-Planck-Institut für Radioastronomie at Bonn, employing the 100-m telescope at Effelsberg for the original detection and the Very Large Array in New Mexico for confirmation.
ATLASGAL: the APEX survey of cold dust in our Milky Way
Wyrowski, Friedrich; Schuller, Frédéric; Menten, Karl M. (2009)
The ATLASGAL project is a complete survey of cold dust in our Milky Way using the new submillimeter bolometer camera at the APEX telescope. Our goal is to produce a large scale, systematic database of massive clumps in the Galaxy, in order to better understand how and under which conditions star formation takes place. Such a systematic survey at submillimeter wavelengths also represents a pioneering work for the preparation of Herschel and ALMA.
Infrared interferometry of the enigmatic star η Carinae
Driebe, Thomas; Hofmann, Karl-Heinz; Kraus, Stefan; Schertl, Dieter; Weigelt, Gerd (2008)
Observations with the Very Large Telescope Interferometer of the European Southern Observatory allowed the first spectro-interferometric studies of the enigmatic Luminous Blue Variable η Carinae with high spectral resolution [1]. The aim of this work was to study the opaque stellar wind of η Carinae with a high angular resolution of 5 milli-arcseconds.
The Inner Jet of the Radio Galaxy M87
Yuri Kovalev (2008)
A new image of the inner jet of the radio galaxy M87 was produced in the Max-Planck-Institute for Radioastronomy. It is unprecedented in its combination of sensitivity and spatial resolution, providing details down to only three light months in size. It shows a highly collimated jet which appears limb-brightened and also a faint counter-jet which are analyzed within the framework of the current theoretical models.
First results with the Atacama Pathfinder Experiment
Wyrowski, Friedrich; Menten, Karl M. (2007)
The Atacama Pathfinder Experiment 12-m sub-millimeter telescope lives up to the ambitions of the scientists by providing access to the "Cold Universe" with unprecedented sensitivity and image quality. Most of the new findings are in the field of star formation and astrochemistry: observations of molecular outflows allow the study of the earliest phases of star formation, mapping of giant molecular clouds reveals details of early evolutionary phases of massive stars, and finally, a new interstellar molecule was for the first time detected with the new telescope.
LOFAR - A New Generation of Radio Telescopes
Beck, Rainer; Reich, Wolfgang (2006)
LOFAR, the Low Frequency Array, is a new radio telescope under construction by ASTRON in the Netherlands, operating in the largely unexplored frequency range between 30 and 240 MHz. The radio images are synthesized in a supercomputer in real time from the digital signals of simple dipoles in 77 stations in the Netherlands and at least 12 stations in Germany. The first German station will be built in 2006 next to the 100-m Effelsberg radio telescope.
Infrared Interferometry of the active galaxy NGC 1068
Beckert, Thomas; Hofmann, Karlheinz; Hönig, Sebastian; Schertl, Dieter; Weigelt, Gerd (2005)
Speckle-interferometric observations as well as long-baseline interferometry with the instruments VINCI and MIDI at the Very Large Telescope Interferometer (VLTI) have allowed the resolution of the nucleus of the Active Galaxy NGC 1068 at infrared wavelengths in the range of 1,65 to 13 µm. Therefore, it is now possible, for the first time, to investigate the inner torus region around NGC 1068’s Black Hole and to test model predictions.
The Sharpest View of the Universe: New Frontiers in Very-Long-Baseline Interferometry
Middelberg, Enno; Brunthaler, Andreas; Falcke, Heino; Greenhill, Lincoln L.; Henkel, Christian; Reid, Mark; Roy, Alan L.; Walker, R. Craig (2005)
Recent progress in Very-Long-Baseline Interferometry has brought the technique to a new frontier. This technique provides the highest resolution in astronomy. Challenging observations are performed at very high frequencies, where the effects of the changing atmosphere together with the lower sensitivity of the receivers make observations much more difficult. A new calibration technique has been developed at the Max Planck Institute for Radio Astronomy in Bonn to perform successful observations at a wavelength of 3 millimeter by extrapolating quasi-simultaneous observations at lower frequencies. Another spectacular result is the measurement, for first the time, of the motion of a neighbour galaxy from very precise astrometric observations. The motion of the galaxy M33 in the Local Group was successfully determined with micro-arcsecond precision. In both cases, the results were obtained by graduate students in the framework of the International Max Planck Research School for Radio and Infrared Interferometry.
The search for biomolecules in the interstellar medium
Menten, Karl M. (2004)
The availability of innovative detectors at the world's most powerful radio and (sub)millimeter telescopes has opened new vistas in the search for complex organic molecules in the interstellar medium. In particular, in the dense, warm envelopes of luminous protostars one detects ever more complex chemical compounds. The neighborhood of our Galactic center, which is filled with dense, hot molecular clouds, is of special interest: Here one detects a greater variety of such molecules than anywhere else.
High resolution studies of active galactic nuclei
Huege, Tim; Kadler, Matthias; Ros, Eduardo; Witzel, Arno; Zensus, Anton (2004)
The central region of Active Galactic Nuclei (AGN) are the main research topic of the group headed by Dr. Anton Zensus. The regions surrounding the nuclear engines (supermassive black holes) are observed using radio interferometry with Very Long Baselines (VLBI). By comparison with observations of AGN in all accessible wavelength ranges, detailed physical models for these most energetic objects in the Universe are made. In addition cosmological questions are investigated, especially questions concerning the cosmic microwave background (CMB).