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Sydney Barnes, leader of the stellar activity group at AIP and organizer of the conference, states: “This rotation seems to be the fundamental variable underlying many dynamical behaviors of stars such as the magnetic activity manifested in stellar dynamos, starspots, and solar or stellar flares. One application of measured stellar rotation rates is to derive the ages of stars, otherwise difficult to obtain.” These ages are helping to construct astronomical chronologies, that is, the dating of astronomical phenomena. Silva Järvinen, AIP-scientist in the stellar physics and exoplanets section, adds: “The AIP has played a leading role over the past decades in efforts to understand these magnetic phenomena for a large variety of stars, and also to measure related manifestations such as starspots, stellar magnetic fields, and rotation itself.” The rotation rates of increasingly large numbers of stars can now be measured precisely using telescopes on earth and also in space.

This conference will bring together an international cross-section of major contributors to the field to discuss the latest findings, and to put them in perspective. More information on this event is available at the conference website: https://thinkshop.aip.de/16.

Scientific contacts

Dr. Sydney Barnes, 0331-7499-379, sbarnes@aip.de

Dr. Silva Järvinen, 0331-7499-448, sjarvinen@aip.de

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.

The Large Magellanic Cloud is one of our nearest galactic neighbors, at only 163 000 light years from Earth. With the Small Magellanic Cloud, these are among the nearest dwarf satellite galaxies to the Milky Way. The Large Magellanic Cloud is also the home of various stellar conglomerates and is an ideal laboratory for astronomers to study the processes that shape galaxies.

ESO’s VISTA telescope has been observing these two galaxies for the last decade. The main goal of the VISTA Magellanic Clouds Survey has been to map the star formation history of the Large and Small Magellanic Clouds, as well as their three-dimensional structures. “Our section is leading the VISTA survey of the Magellanic Clouds system and has been awarded an ERC consolidator grant for using the Magellanic Clouds to study the interaction of galaxies,” states Maria-Rosa Cioni, head of the Dwarf galaxies and the Galactic Halo section at AIP and principle investigator of the survey.

VISTA was key to this image because it observes the sky in near-infrared wavelengths of light. This allows it to see through clouds of dust that obscure parts of the galaxy. These clouds block a large portion of visible light but are transparent at the longer wavelengths VISTA was built to observe. As a result, many more of the individual stars populating the centre of the galaxy are clearly visible. Astronomers analysed about 10 million individual stars in the Large Magellanic Cloud in detail and determined their ages using cutting-edge stellar models. They found that younger stars trace multiple spiral arms in this galaxy.

For millennia, the Magellanic Clouds have fascinated people in the Southern Hemisphere, but they were largely unknown to Europeans until the 16th century. The name we use today harkens back to Ferdinand Magellan, who 500 years ago began the first circumnavigation of the Earth. The records the expedition brought back to Europe revealed many places and new knowledge to Europeans for the first time. The spirit of exploration and scientific curiosity is ever more live today in the work of astronomers around the world, including the VMC team whose observations led to this stunning image of the Large Magellanic Cloud.

These cutouts highlight some of the most spectacular regions in the Large Magellanic Cloud. Credit: ESO/VISTA VMC

ESO press release

https://www.eso.org/public/news/eso1914/

More about VISTA

http://bit.ly/ESO_VISTA

Science contact

Prof. Dr. Maria-Rosa Cioni, 0331-7499-651, mcioni@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.

Ever since the earliest theoretical predictions 20 years ago, the chemical elements potassium and sodium were expected to be detectable in atmospheres of “hot Jupiters”, gaseous planets with temperatures of a few thousand Kelvin that orbit closely around far-away stars. While sodium was detected with high resolution observations already early on, potassium was not, which created a puzzle for atmospheric chemistry and physics.

The elements can be discovered by analyzing the home star’s spectrum of light when the planet passes in front of it as seen from Earth. Different elements cause specific absorption signals in the spectrum, dark lines, that hint at the chemical composition of the atmosphere. However, the presence of clouds in hot Jupiter atmospheres strongly weakens any spectral absorption features and thus makes them very hard to detect. Even for HD189733b, the best studied hot Jupiter, so far scientists only possessed a very vague and imprecise knowledge of the potassium absorption. The exoplanet, 64 light years away and about the size of Jupiter, orbits its home star – a dwarf star with 0,8 times the mass of the Sun – in 53 hours and is 30 times closer to it than the Earth to the Sun. It needed the light gathering capability of the 2x8,4m LBT and the high spectral resolution of PEPSI to definitely measure potassium for the first time at high resolution in atmospheric layers above the clouds. With these new measurements, researchers can now compare the absorption signals of potassium and sodium and thus learn more about processes such as condensation or photo-ionization in these exoplanet atmospheres.

The technique that was applied for this study at LBT is called transmission spectroscopy. It requires that the exoplanet transits in front of the host star. “We took a time series of light spectra during the transit and compared the absorption depth,” says the lead author of the study, Engin Keles, PhD student at AIP in the group Stellar Physics and Exoplanets. “During transit, we then detected the potassium signature, which disappeared before and after transit as expected, which indicates that the absorption is induced by the planetary atmosphere.” Investigations by other teams already attempted to detect potassium on the same exoplanet, however, either nothing was found or what was found was too weak to be statistically significant. Until now there has been no significant detection of potassium in high resolution observations for any exoplanet. “Our observations clearly made the breakthrough” emphasizes project co-leader Dr. Matthias Mallonn, who is seconded by PEPSI’s principal investigator Prof. Klaus Strassmeier:  “PEPSI is well suited for this task because of its high spectral resolution that allows collecting more photons per pixel from very narrow spectral lines than any other telescope-spectrograph combination.” “Both as a spectrograph and as a spectropolarimeter, PEPSI has already made significant contributions to stellar physics,” adds Christian Veillet, LBT Observatory's Director. “This strong detection of potassium in the atmosphere of an exoplanet establishes PEPSI as an amazing tool for exoplanet characterization as well as a unique asset for the members of the LBT community.” The team included colleagues from Denmark, The Netherlands, Switzerland, Italy and the United States andhas now presented the results in the journal Monthly Notices of the Royal Astronomical Society.

LBT press release

http://lbtonews.blogspot.com

More information on PEPSI

https://pepsi.aip.de

Images and Video

https://cloud.aip.de/index.php/s/nwaLMDGcjQHXBzM

Science contacts

Engin Keles, 0331-7499-538, ekeles@aip.de

Prof. Dr. Klaus G. Strassmeier, 0331-7499-223, kstrassmeier@aip.de

Media contact

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

Original Publication

Engin Keles, Matthias Mallonn, Carolina von Essen, Thorsten A. Carroll, Xanthippi Alexoudi, Lorenzo Pino, Ilya Ilyin, Katja Poppenhäger, Daniel Kitzmann, Valerio Nascimbeni, Jake D. Turner, Klaus G. Strassmeier (2019), MNRAS, “The potassium absorption on HD189733b and HD209458b” https://doi.org/10.1093/mnrasl/slz123

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.

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.