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The ultimate RAVE: final data release published

RAVE observed nearly half a million stars of our Galaxy. The Sun is located at the centre of the coordinate system. Credit: AIP/K. Riebe, the RAVE Collaboration; Milky Way image (background): R. Hurt (SSC); NASA/JPL-Caltech

The ultimate RAVE: final data release published

27 July 2020. How do the stars in our Milky Way move? For more than a decade RAVE, one of the first and largest systematic spectroscopic surveys, studied the motion of Milky Way stars. The RAVE col...

The RAdial Velocity Experiment RAVE is a spectroscopic survey of stars in the southern hemisphere. RAVE was designed to get a representative census of the movements and of the atmospheric properties of stars in the wider neighbourhood of the Sun. By means of spectroscopy, the light of a star is decomposed into its rainbow colours. By analysing the spectra, the radial velocity of a star – the movement of the stars in the direction of the observer's view, can be determined. Furthermore, stellar spectra also enable scientists to determine stellar parameters like temperatures, surface gravities, and composition. In order to trace the structure and shape of our galaxy, RAVE successfully measured 518,387 spectra for 451,783 Milky Way stars.

Astronomers are not only used to think in long time scales – their projects also are often many-year endeavours. RAVE observed the sky for almost every clear night between 2003 and 2013 at the 1.2-metre UK Schmidt telescope of the Anglo-Australian Observatory in Siding Spring, Australia. RAVE utilized a dedicated fibre-optical setup to simultaneously take spectra of up to 150 stars in a single observation. Only with this massive multiplexing such a large number of targets was achievable – the largest spectroscopic survey before RAVE featured only some 14000 targets. In this way the survey obtained a representative sample of the stars around our Sun that are located roughly in a volume 15000 light years across.

Over the past 15 years, an increasing number of stars and refined data products have been released. The final RAVE data release not only provides for the first time the spectra of all stars in the RAVE sample; the stars were also matched with stars from the DR2 catalogue of the satellite mission Gaia. Thanks to the exquisite distances and proper motions measured by Gaia, considerably improved stellar temperatures, surface gravities and the chemical composition of the stellar atmospheres could be derived.

“The RAVE data releases have provided new insights into the motion of stars and chemical structure of our Milky Way,” says Matthias Steinmetz, leader of the RAVE collaboration and scientific chairman of the Leibniz Institute for Astrophysics Potsdam (AIP). “The final data release concludes one of the first systematic spectroscopic Galactic Archaeology surveys. It’s really exciting to think about finishing this 15-year project. Thanks to RAVE, we have gained new insights into the structure and composition of our Milky Way. “ ­­

Some of the key results of RAVE include the determination of the minimum speed needed for a star to escape the gravitational pull of the Milky Way. The results confirmed that dark matter, an invisible component of the Universe of yet unknown nature, dominates the mass of our Galaxy. With RAVE it could be shown that the Milky Way disk is asymmetric and wobbles owing to the interaction with spiral arms and the infall of satellite galaxies. RAVE also allowed for the identification of stellar streams in the solar environment. These streams of stars are the residues of torn apart old dwarf galaxies that have merged into our Milky Way in the past. The chemical element abundances of the observed stars hold important clues to the chemical composition and the subsequent metal enrichment of the interstellar medium traced by stars of different ages and metallicities. With RAVE, astronomers efficiently searched for the very first stars, which are very metal-poor and give clues about the earliest epochs of star formation and the chemical evolution in the Milky Way.

The RAVE collaboration consists of researchers from over 20 institutions around the world and is coordinated by the AIP. More than 100 refereed scientific articles based on RAVE data were published since the first data release.

 

RAVE observed nearly half a million stars of our Galaxy. The Sun is located at the centre of the coordinate system. The colours represent radial velocities: red are receding stars and stars depicted in blue are approaching. Credit: AIP/K. Riebe, the RAVE Collaboration; Milky Way image (background): R. Hurt (SSC); NASA/JPL-Caltech

Map of the night sky centered on the Milky Way, with stars observed by RAVE. More than 6000 observation fields mainly from the southern sky (below the celestial equator, red line) with about half a million stars have been observed. Credit: AIP/K. Riebe, the RAVE Collaboration; Milky-Way image (background): ESO/S. Brunier

The stars observed by RAVE are from the southern celestial hemisphere, since the UK-Schmidt telescope is located in Australia. There are only a few observation fields in the area of the Milky Way disk (central part), because in this crowded area it is much harder to collect and analyse individual stars. Credit: AIP/K. Riebe, the RAVE Collaboration

This movie shows the stars observed by RAVE from 2003 to 2013, first on a map of the sky and then their 3D distribution in the Milky Way. Colouring stars by metallicity reveals the trend for lower metallicities at larger distances from the Galactic plane. Credit: AIP/K. Riebe, the RAVE Collaboration; Milky-Way images (background): ESO/S. Brunier, R. Hurt (SSC), NASA/JPL-Caltech

 

Science contact
Prof. Dr. Matthias Steinmetz, 0331 7499 800, msteinmetz@aip.de

Media contact
Franziska Gräfe, 0331 7499 803, presse@aip.de

 

RAVE Website

www.rave-survey.org

Publications

The Sixth Data Release of the Radial Velocity Experiment (RAVE) -- I: Survey Description, Spectra and Radial Velocities

arXiv: https://arxiv.org/abs/2002.04377

Astronomical Journal: https://iopscience.iop.org/article/10.3847/1538-3881/ab9ab9

The Sixth Data Release of the Radial Velocity Experiment (RAVE) -- II: Stellar Atmospheric Parameters, Chemical Abundances and Distances

arXiv: https://arxiv.org/abs/2002.04512

Astronomical Journal: https://iopscience.iop.org/article/10.3847/1538-3881/ab9ab8

 

The key areas of research at the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. The AIP has been a member of the Leibniz Association since 1992.

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First images of the Sun from Solar Orbiter

The image shows the Sun’s appearance at a wavelength of 17 nanometers, which is in the extreme ultraviolet region of the electromagnetic spectrum. Credit: Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL

First images of the Sun from Solar Orbiter

16 July 2020. Solar Orbiter, a mission of the space agencies ESA and NASA, publishes for the first time images that show our home star as close as never before. Prior to this, the test phase of all...

Five months ago Solar Orbiter started its journey to the Sun. Between mid-March and mid-June, the ten instruments on board were switched on and tested, and the spacecraft made its first approach to the Sun. Shortly afterwards, the international science teams were able to test all instruments together for the first time.

In addition to visible light, the Sun also emits X-rays, especially during solar flares. The Leibniz Institute for Astrophysics Potsdam (AIP) is mainly involved in the mission with the X-ray telescope STIX (Spectrometer/Telescope for Imaging X-Ray). With this instrument it is possible to observe particularly hot regions that are only formed during solar flares. The rest of the Sun is not visible in X-rays, so STIX needs its own system that precisely measures its orientation towards the Sun. The team at the AIP developed and built the STIX Aspect System (SAS) and now operates it during the mission. This allows the X-ray images to be correlated with the images of the other instruments.

The first images taken by Solar Orbiter from the Sun, which have now been published, reveal previously unknown details. They show numerous small solar flares, so-called "campfires". This already illustrates the enormous potential of the mission, whose scientific phase will begin in November 2021 and continue until 2029.

"All STIX instrument parts, such as the 32 X-ray detectors, worked as expected. We solar physicists at the AIP of course were very excited. To our delight we see that SAS is delivering good data as expected. During the test phase, we were able to see how the diameter of the Sun is constantly increasing as the probe approaches the Sun," explains Gottfried Mann, head of the STIX team at the AIP.

On February 10, 2020, the Solar Orbiter spacecraft was launched. The mission will orbit the Sun in the next few years and approach it to a distance of 42 million kilometres. Solar Orbiter carries six remote sensing instruments and telescopes that image the Sun and its surroundings, as well as four in-situ instruments that measure the properties in the environment of the spacecraft. By comparing the data from the two sets of instruments, science will gain insights into the origin of the solar wind - the stream of charged particles from the Sun that affects the entire solar system.

During eruptions on the Sun, an enormous amount of high-energy electrons are generated. These electrons play an important role because they carry a large part of the energy released during the eruption. The AIP is also involved in the Energetic Particle Detector (EPD). EPD can directly measure these electrons when they hit the probe. Thanks to DLR-funded participation in the STIX and EPD instruments, the AIP will be able to investigate the processes of the high-energy electrons in their entirety in the next few years. Solar activity - also known as space weather - can have a major impact on our climate and technical civilisation. Solar Orbiter aims to study the processes on the Sun and their effects on our Earth.

 

Schematic view of Solar Orbiter with all instruments on board. Credit: ESA.

 

Science contact AIP

Prof. Dr. Gottfried Mann, 0331 7499 292, gmann@aip.de

Media contact AIP

Franziska Gräfe, 0331 7499 803, presse@aip.de

ESA press release

https://bit.ly/ESA_SolarOrbiter

 

The key areas of research at the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. The AIP has been a member of the Leibniz Association since 1992.

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Joseph Whittingham receives study prize for physics

Joseph Whittingham. Credit: private

Joseph Whittingham receives study prize for physics

9 July 2020. The Physikalische Gesellschaft zu Berlin (PGzB) awards the student for his master thesis, which he completed in the Department of Cosmology and High Energy Astrophysics at the Leibniz ...

In his master thesis, titled "The Impact of Magnetic Fields on Cosmological Galaxy Mergers", Joseph Whittingham investigated the influence of magnetic fields on galaxy mergers. He accomplished this by running cosmological "zoom-in" simulations of such mergers. He compared simulations that took magnetic fields into account with those that did not. "Somewhat unexpectedly, the two types of simulation yielded significantly different results of galaxy mergers - until this point, the influence of magnetic fields on these cosmological events was generally considered unimportant," states Whittingham. He was able to show that the result was generated mainly thanks to sufficient resolution. This explains to some extent why the correlation has not been recognized in this form so far. Prof. Christoph Pfrommer from the AIP and Dr. Martin Sparre from the University of Potsdam supervised the work.

For his PhD, Whittingham will continue to work with Christoph Pfrommer and use similar types of simulation to investigate the mechanisms behind so-called "radio relics" and other sources of non-thermal emission in galaxy clusters.

The Physics Study Prize of the Physikalische Gesellschaft zu Berlin (PGzB) is awarded for outstanding degrees in the field of physics. This year's award ceremony will take place on 9 July 2020 in the Magnus-Haus in Berlin. Students completing their master’s at the AIP were also awarded last year, when Timon Thomas and Ekaterina Ilin each received the prize.

The AIP congratulates the award-winning student on his outstanding graduation.

 

Media contact: Franziska Gräfe, 0331-7499-803, presse@aip.de

News on the PGzB site: https://www.pgzb.tu-berlin.de/index.php?id=29

 

The key areas of research at the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. The AIP has been a member of the Leibniz Association since 1992.

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The X-ray sky in its full glory

Cosmic X-ray echo. Credit: AIP/G. Lamer, Davide Mella

The X-ray sky in its full glory

19 June 2020. The eROSITA space telescope has provided a new, sharp 360° view of the hot and energetic processes across the Universe. The new map contains more than one million objects, roughly do...

Over the course of 182 days, the eROSITA X-ray telescope has completed its first survey of the full sky. Most of the new sources are active galactic nuclei at cosmological distances, marking the growth of gigantic black holes over cosmic time. Clusters of galaxies in the new map will be used to track the growth of cosmic structures and constrain cosmological parameters.

“The completion of the first all sky survey fills us with great satisfaction and some pride. Since 2006, we have been planning the mission and the scientific yield. The fact that we were able to create a complete, detailed image of the X-ray sky less than 11 months after the launch of eROSITA makes us euphoric about the full scientific harvest,” says Dr. Axel Schwope, project manager at the AIP. “The celestial observations with eROSITA will continue until 2023 and promise many interesting discoveries in the relatively unexplored X-ray light of space.”

The AIP team has already made a surprising discovery. The astronomers found a very special object during their observations with the X-ray telescope: a closed, luminous ring. It was discovered when eROSITA scanned over a region in the southern Milky Way in February 2020. The ring is caused by X-rays scattered in a dust cloud in the plane of the Milky Way. The origin of the radiation is a faint blue source in the centre of the ring, assumed to be a black hole accompanied by a companion star. One year before, a massive outburst of this object was recorded by other X-ray telescopes. For several weeks, it was 10,000 times brighter than at present.

At the time when eROSITA registered this image, the central source appeared inconspicuous again. However, a tiny fraction of the burst radiation was scattered by a dust cloud on its thousands-year-long travel through interstellar space. Due to this detour the scattered X-rays arrived one year after the direct radiation from the burst, similar to an echo. This extra travel causes the apparent ring which will grow with time before becoming too faint to be observable. While a few dust scattering rings were observed in the past around other transient X-ray sources, with an angular diameter of more than twice the size of the full moon the new structure is by far the largest of its kind. Dr. Georg Lamer of the AIP, who discovered the object in the eROSITA data, emphasises its importance: “Apart from the stunning beauty of the image, the discovery is also scientifically valuable, since it may help to measure a precise distance to the black hole.”

eROSITA is an X-ray telescope built by a German consortium under the leadership of the MPE Garching and one of the two telescopes on the Russian-German Spectrum-X-Gamma (SRG) satellite. The satellite was successfully launched on July 13, 2019, with a Proton-M rocket from Baikonur. eROSITA will perform several all-sky X-ray surveys. The AIP contributed to the data reduction software system with special emphasis on the attitude solution system and the source detection software. The institute also provided flight hardware for the camera filter wheels and the whole mechanical ground segment for integration and tests of the X-ray telescope array.

 

The energetic universe as seen with the eROSITA X-ray telescope. Credit: Jeremy Sanders, Hermann Brunner and the eSASS team (MPE); Eugene Churazov, Marat Gilfanov (on behalf of IKI)

 

MPE press release

http://www.mpe.mpg.de/7461761/news20200619

Science contact AIP

Dr. Axel Schwope, 0331 7499 232, aschwope@aip.de

Media contact AIP

Sarah Hönig, 0331 7499 803, presse@aip.de

 

The key areas of research at the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. The AIP has been a member of the Leibniz Association since 1992.

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Four newborn exoplanets get cooked by their sun

Artist's impression of the extrasolar planet system around the star V1298 Tau. Credit: AIP/J. Fohlmeister

Four newborn exoplanets get cooked by their sun

11 June 2020. Scientists from the Leibniz Institute for Astrophysics Potsdam (AIP) examined the fate of the young star V1298 Tau and its four orbiting exoplanets. The results show that these recent...

Young exoplanets live in a high-stakes environment: their sun produces a large amount of energetic X-ray radiation, typically one thousand to ten thousand times more than our own Sun. This X-ray radiation can heat the atmospheres of exoplanets and sometimes even boil them away. How much of an exoplanet's atmosphere evaporates over time depends on the properties of the planet – its mass, density, and how close it is to its sun. But how much can the star influence what happens over billions of years? This is a question that astronomers at the AIP chose to tackle in their newest paper.

The recently discovered four-planet system around the young sun V1298 Tau is a perfect test bed for this question. The central star is about the same size as our Sun. However, it is only about 25 million years old, which is much younger than our Sun with its 4.6 billion years. It hosts two smaller planets – roughly Neptune-sized – close to the star, plus two Saturn-sized planets farther out. “We observed the X-ray spectrum of the star with the Chandra space telescope to get an idea how strongly the planetary atmospheres are irradiated,” explains Katja Poppenhäger, the lead author of the study. The scientists determined the possible fates of the four exoplanets. As the star-planet system grows older, the rotation of the star slows down. The rotation is the driver for the star’s magnetism and X-ray emission, so slower rotation goes hand in hand with weaker X-ray emission. “The evaporation of the exoplanets depends on whether the star spins down quickly or slowly over the next billion years – the faster the spin-down, the less atmosphere is lost,” says PhD student and co-author Laura Ketzer, who developed a publicly available code to calculate how the planets evolve over time.

The calculations show that the two innermost planets of the system may lose their gas atmospheres completely and become rocky cores if the star spins down slowly, while the outermost planet will continue to be a gas giant. “For the third planet, it really depends on how heavy it is, which we don't know yet. Measuring the size of exoplanets with the transit technique works well, but determining planetary masses is much more challenging,” explains co-author Matthias Mallonn, who has updated the transit properties of the system using observations with AIP's ground-based STELLA telescope.

“X-ray observations of stars with planets are a key puzzle piece for us to learn about the long-term evolution of exoplanetary atmospheres,” concludes Katja Poppenhäger. “I am particularly excited about the possibilities we get through X-ray observations with eROSITA over the next few years.” The eROSITA X-ray telescope, which has been developed in part by the AIP, is conducting observations of the whole sky and will yield X-ray properties for hundreds of exoplanet host stars.

 

Science contact:

Prof. Dr. Katja Poppenhäger, 0331 7499 521, kpoppenhaeger@aip.de

Media contact:

Sarah Hönig, 0331 7499 803, presse@aip.de

Publication:

https://doi.org/10.1093/mnras/staa1462

https://arxiv.org/abs/2005.10240

Public code:

https://github.com/lketzer/platypos/

 

The key areas of research at the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. The AIP has been a member of the Leibniz Association since 1992.

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