News

With the use of additional optical and infrared photometry from ground-and space-based telescopes, scientists of AIP and the Institute of Cosmos Sciences of the University of Barcelona have recently determined new distances, stellar properties and interstellar dust extinctions for about 150 million stars in our Galaxy. This multi-wavelength approach especially allows for a more accurate mapping of the most distant regions of the Milky Way, extending the three-dimensional view of the Milky Way beyond previous works and for the first time clearly mapping the central Galactic bar.

“We looked in particular at two of the stellar parameters contained in the Gaia data: the surface temperature of stars and the ‘extinction’, which is basically a measure of how much dust there is between us and the stars, obscuring their light and making it appear redder,” says Dr. Friedrich Anders from University of Barcelona, lead author of the new study. “These two parameters are interconnected, but we can estimate them independently by adding extra information obtained by peering through the dust with infrared observations.”

The team combined the second Gaia data release with several infrared surveys using a computer code called StarHorse, developed by co-author Anna Queiroz, PhD student in the Milky Way and Local Volume group at AIP, and collaborators. The code compares the observations with stellar models to determine the surface temperature of stars, the extinction and an improved estimate of the distance to the stars. Dr. Arman Khalatyan, member of the Supercomputing and E-Science group at the AIP and second author of the article, underlines that “in total, the computation would have taken 19 years on a single computer. And with the growing amount of data, even bigger efforts will be necessary in the future.” The computations were conducted at the cluster facility of AIP.

As a result, the astronomers obtained much better determination of the distances to about 150 million stars – in some cases, the improvement is up to 20% or more. This enabled them to trace the distribution of stars across the Milky Way to much greater distances than possible with the original Gaia data alone. “With the second Gaia data release, we could probe a radius around the Sun of about 6500 light years, but with our new catalogue, we can extend this ‘Gaia sphere’ by three or four times, reaching out to the center of the Milky Way,” explains co-author Dr. Cristina Chiappini, staff scientist in the AIP's Milky Way and Local Volume group.

There, at the center of our galaxy, the data clearly reveals a large, elongated feature in the three-dimensional distribution of stars: the galactic bar. “We know the Milky Way has a bar, like other barred spiral galaxies, but so far we only had indirect indications from the motions of stars and gas, or from star counts in infrared surveys. This is the first time that we see the galactic bar in 3D space, based on geometric measurements of stellar distances,” says Anders.

“Ultimately, we are interested in galactic archaeology: we want to reconstruct how the Milky Way formed and evolved, and to do so we have to understand the history of each and every one of its components,” adds Chiappini. “It is still unclear how the bar – a large amount of stars and gas rotating rigidly around the center of the galaxy – formed, but with Gaia and other upcoming surveys in the next years we are certainly on the right path to figure it out.”

Next Gaia data releases & follow-up spectroscopic surveys

Looking ahead, Queiroz is excited that "with the upcoming Gaia data release, which will also include low-resolution spectra for billions of stars, we can produce even better Galactic maps, possibly reaching the other side of the Galactic disc." The third Gaia data release, currently planned for 2021, will include greatly improved distance determinations for a much larger number of stars, and is expected to enable progress in our understanding of the complex region at the center of the Milky Way.

Chiappini adds: "Spectroscopic follow-up surveys using dedicated earthbound telescopes will provide complementary information, in particular radial velocities and detailed chemical composition fingerprints for many millions of stars. Combined with Gaia, these surveys, among them the 4-metre Multi-Object Survey Telescope (4MOST) at the European Southern Observatory and the WEAVE survey at the William Herschel Telescope in La Palma, will allow us to unfold the assembly history of the Milky Way in a much more detailed fashion."

ESA press release

http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_starts_mapping_our_galaxy_s_bar

Data access

https://data.aip.de/projects/starhorse2019.html (doi:10.17876/gaia/dr.2/51)

3D Visualization Video

https://escience.aip.de/vis/starhorse-2019/

Scientific contact AIP

Dr. Cristina Chiappini, 0331-7499-454, cristina.chiappini@aip.de

Dr. Arman Khalatyan, 0331-7499-528, akhalatyan@aip.de

Media contact AIP

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

Publication

F. Anders, A. Khalatyan, C. Chiappini, A. Queiroz, et al. (2019), Astronomy and Astrophysics, "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18"

https://doi.org/10.1051/0004-6361/201935765

The international CESRA conference takes place every three years and is organized by the Community of European Solar Radio Astronomy (CESRA). CESRA is an association of European scientists to study the solar corona, the outer solar atmosphere, and interplanetary space using radio waves and other observation methods.

The topics of this year's CESRA workshop range from solar flares and shock waves to the turbulent solar atmosphere, new observation instruments and space weather. The heliosphere, i.e. the area around the sun, is of particular interest as magnetic fields and solar winds play an important role here.

"We are pleased to welcome colleagues from four continents to Potsdam's Telegrafenberg. It is an honour for us to host this conference this year. The last time it was in Caputh in 1994", says Prof. Dr. Gottfried Mann, head of the "Solar Physics" department at the AIP. In the coming years, great progress in solar physics is expected with the space missions "Parker Solar Probe" of NASA and "Solar Orbiter" of the European Space Agency ESA. The AIP is involved in both missions with scientific investigations and, in the case of the "Solar Orbiter", even with instruments, in particular the X-ray telescope STIX. About 100 scientists are expected. "There will be many interesting discussions that will stimulate our work in the coming years", says Gottfried Mann. The fact that this year's conference will take place in Potsdam shows the international recognition that Potsdam's solar physics enjoys.

More information on the conference with conference programme:

https://meetings.aip.de/cesra2019/

Press contact 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.

The Russian-German mission will provide the first complete sky survey in the medium X-ray range. eROSITA will study the distribution of huge galaxy clusters and find out more about the mysterious dark energy that influences their formation and evolution. It is expected to detect about 100,000 clusters of galaxies, the largest gravitationally bound objects, which map the large-scale structure of the universe and provide insights into how it is expanding. An estimated three million active galactic nuclei (AGN) containing massive black holes will be discovered. Within our Milky Way, eROSITA will discover about 700,000 active stars and 10,000 compact objects including binary stars and stellar explosions such as supernovae and their remnants.

eROSITA (extended Roentgen Survey with an Imaging Telescope Array) is an X-ray telescope built by a German consortium under the leadership of theMax Planck Institute for Extraterrestrial Physicsin Garching. The Leibniz Institute for Astrophysics Potsdam (AIP) contributed to the data reduction software system with special emphasis on the attitude solution system and the source detection. AIP also provided flight hardware for the camera filter wheels and the whole mechanical ground segment equipment for integration and tests of the X-ray telescope array.

"We have come a long way. Behind us lie 12 years of preparation with ups and downs. A real highlight is right ahead of us and, naturally, we feel a growing tension whether everything will work out,” says Axel Schwope, eROSITA project leader at AIP. “Our position-determining software will be called into action a few days after the launch and after all the tests its components will soon have to prove their suitability in space. We are proud that eROSITA, the main instrument aboard SRG (Spectrum X-Ray Gamma), has been assembled in the integration and test rig we delivered." Prof. Matthias Steinmetz, scientific director of the AIP, emphasizes that "a few parts Made-in-Potsdam, holders of the calibration sources in the 7 filter wheels, are also onboard."

The approved mission time is seven years. During the first four years of the mission, eight independent all-sky X-ray surveys will be performed. An operational phase with pointed observations will follow and last for 2.5 years. “The X-ray images and the catalogues – the basis for a scientific evaluation – will be created with our software. The first data which is specifically for us at the AIP will be recorded in October and we will virtually leap at it,” adds project scientist Dr. Georg Lamer. “After six months, eROSITA will have found more sources of X-ray radiation in the sky than in the first 50 years of X-ray astronomy. For now, we will celebrate these great prospects.”

Members of AIP are also participating in the eROSITA scientific working groups. Optical identification of new X-ray sources is of major relevance: The eROSITA cluster and AGN surveys were selected as design reference surveys for the future 4MOST facility, a 4-meter multi-object spectroscopic telescope for the European Southern Observatory ESO, currently under construction lead by the AIP.

Livestream of the rocket launch

http://www.tvroscosmos.ru/5129/

MPE about eROSITA

http://www.mpe.mpg.de/eROSITA

DLR press release

http://bit.ly/DLR_eROSITA_EN

Scientific contact

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

Press contact

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.

The master thesis of Ekaterina Ilin, supervised by Prof. Klaus Strassmeier and Dr. Sydney Barnes, was dedicated to the statistical description of radiation outbursts on stars (flares) in open star clusters. To do this, she examined the light curves of small stars for flares and measured how flare frequencies and energies develop with stellar age. Ekaterina Ilin summarizes the results of her work: "I was able to show that the energies decrease with age and that the decrease depends strongly on stellar mass. I would particularly like to thank Dr. Sarah Schmidt, who supported me as a mentor.“ Ekaterina Ilin continues her studies as a PhD student at the AIP in the Stellar Physics and Exoplanets section with Prof. Katja Poppenhäger.

In his master thesis, Timon Thomas generalized the previous hydrodynamic theories for cosmic rays, so that small-scale effects can be better described. The thesis was supervised by Prof. Christoph Pfrommer at the AIP and apl. Prof. Achim Feldmeier at the University of Potsdam. "My area of interest, the physics of cosmic rays, has a simple problem that is difficult to solve: the interesting scales of cosmic rays are far apart. With the development of a new hydrodynamic theory it is easier to bridge the differences in size on a theoretical level," says Timon Thomas about his work. He also continues his research as a PhD student at the AIP, in the Cosmology and High-Energy Astrophysics section with Prof. Christoph Pfrommer.

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 11 July 2019 in the Magnus-Haus in Berlin.

AIP cordially congratulates the two award-winning students on their outstanding graduation.

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

Media contact 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.

Built between 1919 and 1924 according to plans by architect Erich Mendelsohn, the Einstein Tower is not just an architectural masterpiece. The solar telescope was created to prove the redshift of spectral lines through the Sun's gravitational field predicted in Einstein's theory of relativity – the tower is still used for scientific purposes today. On this day visitors will have the rare opportunity to take a look at the laboratory of the Einstein Tower.

In the historic dome hall of the Great Refractor, interested visitors can admire one of the largest refracting telescopes in the world, which is celebrating its 120th birthday this year. Scientists of the AIP give exciting insights into modern research in lectures. Piano sounds fill the room with a special atmosphere before, after dark and with a clear sky, the guests themselves become observers under expert guidance and can take a look through the telescope into the vastness of the cosmos.

Lectures in the seminar room of the Great Refractor (in German):

6 pm: Andrea Diercke – Facets of the Sun: Filaments in various colours

7 pm: Dr. Alexander Warmuth – Departure to the sun: the mission Solar Orbiter

8 pm: Dr. Christian Vocks – The sun - our next star

9 pm: Dr. Horst Balthasar - The Sun and Europe's Largest Solar Telescope GREGOR

In the dome hall:

Handicraft table for children until 8.30pm; Astroquiz (research diploma)

Presentation about the telescope and ist history

from approx. 9.30 pm: Live music – piano and bass with Tinski Music

from approx. 10.30 pm: Observation at the Great Refractor – after dusk and only with a clear view!

The complete programme of the event and information on tickets

https://www.langenachtderwissenschaften.de/index.php?article_id=534