Frank Eisenhauer (born 9 June 1968 in Augsburg) is a German astronomer and astrophysicist, a director of the Max Planck Institute for Extraterrestrial Physics (MPE), [1] and a professor at Technical University of Munich. He is best known for his contributions to interferometry and spectroscopy and the study of the black hole at the centre of the Milky Way.
Eisenhauer grew up in Augsburg. In 1987, he graduated from the Justus-von-Liebig Gymnasium in Neusäß and then did his military service with the Mountain Signal Battalion 8 in Murnau. Eisenhauer is married with three children and lives in Munich.
Eisenhauer studied physics at the Technical University of Munich (1988–1995) and has been working at the Max Planck Institute for Extraterrestrial Physics (MPE) since his diploma thesis in 1995. There, he wrote his doctoral thesis under Reinhard Genzel and received his doctorate from the Ludwig Maximilian University of Munich in 1998. In 2011, Eisenhauer habilitated at the Technical University of Munich.
Eisenhauer is Adjunct Professor at the Technical University of Munich, where he teaches astrophysics and high-resolution astronomy. [2]
As a director of the Max Planck Institute for Extraterrestrial Physics (MPE), Eisenhauer leads the development and scientific evaluation of large astronomical instruments. Eisenhauer has been instrumental in the development of astronomy with the highest spatial resolution and imaging spectroscopy, contributing in particular to the discovery and study of the black hole at the centre of the Milky Way. [3]
Already in his doctoral thesis, Eisenhauer worked on infrared astronomy and developed an infrared camera with Fabry-Pérot spectrometer for the adaptive optics at the 3.6m telescope of the European Southern Observatory (ESO) in La Silla (Chile). Subsequently, as Principal Investigator, he led the development of the SPIFFI/SINFONI spectrometer at the ESO Very Large Telescope in Paranal (Chile), which, with a then unique combination of adaptive optics and imaging spectroscopy, [4] not only corrects for the interference caused by the Earth's atmosphere, but also simultaneously records a spectrum for each pixel in the image. In 2003, this enabled Eisenhauer and colleagues to measure the distance to the centre of the Milky Way from the orbit of the star S2 for the first time using geometric methods, [5] and by measuring the radial velocities of several stars, they were able to confirm the assumption that a supermassive black hole is located there. [6]
Since 2005, Eisenhauer has been principal investigator of the GRAVITY experiment, [7] which connects the European Southern Observatory's four Very Large Telescopes in Paranal, Chile, together as stellar interferometers, achieving an angular resolution equivalent to that of a 130-metre diameter telescope. Similar to adaptive optics, GRAVITY actively corrects for the interfering influences of the Earth's atmosphere and disturbances in the light path between the telescope and the laboratory, improving sensitivity by several orders of magnitude compared to previous experiments. In 2018, this enabled Eisenhauer and colleagues to detect, in particular, the redshift in the gravitational field of a black hole predicted from Albert Einstein's theory of general relativity. [8] The same team also succeeded in 2020 in detecting the Schwarzschild precession (orbit comparison Newton and Einstein) in the orbit of the star S2. [9] The geometric measurement of the distance to the Galactic centre and the detection of the gravitational redshift in the black hole's gravitational field were confirmed by Andrea Ghez and colleagues with observations at the Keck Observatory on Hawaii. [10] [11] [12]
The SINFONI and GRAVITY instruments are part of the instrument suite employed in the discovery and characterization of the Galactic Center Black Hole, for which Reinhard Genzel and Andrea Ghez have been awarded the 2020 Nobel Prize in Physics. [13]
Other areas of research to which Eisenhauer's observations have contributed include galaxy dynamics in the early universe, [14] active galactic nuclei, and star formation in massive star clusters. [15]
The Hyades is the nearest open cluster and one of the best-studied star clusters. Located about 153 light-years away from the Sun, it consists of a roughly spherical group of hundreds of stars sharing the same age, place of origin, chemical characteristics, and motion through space. From the perspective of observers on Earth, the Hyades Cluster appears in the constellation Taurus, where its brightest stars form a "V" shape along with the still-brighter Aldebaran. However, Aldebaran is unrelated to the Hyades, as it is located much closer to Earth and merely happens to lie along the same line of sight.
The Very Large Telescope (VLT) is an astronomical facility operated since 1998 by the European Southern Observatory, located on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each equipped with a primary mirror that measures 8.2 meters in diameter. These optical telescopes, named Antu, Kueyen, Melipal, and Yepun, are generally used separately but can be combined to achieve a very high angular resolution. The VLT array is also complemented by four movable Auxiliary Telescopes (ATs) with 1.8-meter apertures.
The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental research organisation made up of 16 member states for ground-based astronomy. Created in 1962, ESO has provided astronomers with state-of-the-art research facilities and access to the southern sky. The organisation employs over 750 staff members and receives annual member state contributions of approximately €162 million. Its observatories are located in northern Chile.
A supermassive black hole is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (M☉). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, including light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way galaxy has a supermassive black hole at its center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars.
The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact radio source which is almost exactly at the galactic rotational center. The Galactic Center is approximately 8 kiloparsecs (26,000 ly) away from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius, where the Milky Way appears brightest, visually close to the Butterfly Cluster (M6) or the star Shaula, south to the Pipe Nebula.
The Max Planck Institute for Extraterrestrial Physics is part of the Max Planck Society, 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. The scientific activities of the institute are mostly devoted to astrophysics with telescopes orbiting in space. A large amount of the resources are spent for studying black holes in the Milky Way Galaxy and in the remote universe.
Andrea Mia Ghez is an American astrophysicist, Nobel laureate, and professor in the Department of Physics and Astronomy and the Lauren B. Leichtman & Arthur E. Levine chair in Astrophysics, at the University of California, Los Angeles. Her research focuses on the center of the Milky Way galaxy.
Sagittarius A*, abbreviated Sgr A*, is the supermassive black hole at the Galactic Center of the Milky Way. Viewed from Earth, it is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic, visually close to the Butterfly Cluster (M6) and Lambda Scorpii.
The Max-Planck-Institut für Astronomie is a research institute of the Max Planck Society (MPG). It is located in Heidelberg, Baden-Württemberg, Germany near the top of the Königstuhl, adjacent to the historic Landessternwarte Heidelberg-Königstuhl astronomical observatory. The institute primarily conducts basic research in the natural sciences in the field of astronomy.
Reinhard Genzel is a German astrophysicist, co-director of the Max Planck Institute for Extraterrestrial Physics, a professor at LMU and an emeritus professor at the University of California, Berkeley. He was awarded the 2020 Nobel Prize in Physics "for the discovery of a supermassive compact object at the centre of our galaxy", which he shared with Andrea Ghez and Roger Penrose. In a 2021 interview given to Federal University of Pará in Brazil, Genzel recalls his journey as a physicist; the influence of his father, Ludwig Genzel; his experiences working with Charles H. Townes; and more.
The Great Observatories Origins Deep Survey, or GOODS, is an astronomical survey combining deep observations from three of NASA's Great Observatories: the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory, along with data from other space-based telescopes, such as XMM Newton, and some of the world's most powerful ground-based telescopes.
S2, also known as S0–2, is a star in the star cluster close to the supermassive black hole Sagittarius A* (Sgr A*), orbiting it with a period of 16.0518 years, a semi-major axis of about 970 au, and a pericenter distance of 17 light hours – an orbit with a period only about 30% longer than that of Jupiter around the Sun, but coming no closer than about four times the distance of Neptune from the Sun. The mass when the star first formed is estimated by the European Southern Observatory (ESO) to have been approximately 14 M☉. Based on its spectral type, it probably has a mass of 10 to 15 solar masses.
Integral field spectrographs (IFS) combine spectrographic and imaging capabilities in the optical or infrared wavelength domains (0.32 μm – 24 μm) to get from a single exposure spatially resolved spectra in a bi-dimensional region. The name originates from the fact that the measurements result from integrating the light on multiple sub-regions of the field. Developed at first for the study of astronomical objects, this technique is now also used in many other fields, such bio-medical science and Earth remote sensing. Integral field spectrography is part of the broader category of snapshot hyperspectral imaging techniques, itself a part of hyperspectral imaging.
S55 is a star that is located very close to the centre of the Milky Way, near the radio source Sagittarius A*, orbiting it with an orbital period of 12.8 years. Until 2019, when the star S62 became the new record holder, it was the star with the shortest known period orbiting the black hole at the centre of the Milky Way. This beat the record of 16 years previously set by S2. The star was identified by a University of California, Los Angeles team headed by Andrea M. Ghez. At its periapsis, its speed reaches 1.7% of the speed of light. At that point it is 246 astronomical units from the centre, while the black hole radius is only a small fraction of that size. It passed that point in 2022 and will be there again in 2034.
Evolutionary Map of the Universe, or EMU, is a large project which will use the new ASKAP telescope to make a census of radio sources in the sky. EMU is expected to detect about 70 million radio sources. Most of these radio sources will be galaxies millions of light years away, many containing massive black holes, and some of the signals detected will have been sent less than half a billion years after the Big Bang, which created the universe 13.7 billion years ago. Unlike the NVSS, which mainly detected active galactic nuclei, the greater sensitivity of EMU means that about half the galaxies detected will be star-forming galaxies.
The Sagittarius A* cluster is the cluster of stars in close orbit around Sagittarius A*, the supermassive black hole at the center of the Milky Way. The individual stars are often listed as "S-stars", but their names and IDs are not formalized, and stars can have different numbers in different catalogues.
Marc Alexander Rafelski is an American astrophysicist. Rafelski studied astronomy at the University of California, Los Angeles with Andrea Gehz. He obtained his PhD in physics from the University of California, San Diego, under supervision of Arthur Wolfe, in 2011.
Dante Minniti is an astronomer born in Santa Fe, Argentina on December 1, 1962. He has devoted his career to the study of stellar populations, stellar evolution, globular clusters, galaxy formation, gravitational microlensing, exoplanets and astrobiology. He has been member of the SuperMACHO Team since 2001 and leader of the VVV Survey along with Phil Lucas since 2006 and of its extended version, the VVVX Survey. He has also fostered new scientists, supervising 14 PhD students, 11 Master Students and 17 Postdocs. He is Full Professor and Director of the Astronomy Institute at Andrés Bello National University (UNAB), Chile.
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