News

Other Suns got the right spin

17 May 2016. Astrophysicists from the Leibniz Institute for Astrophysics Potsdam (AIP) and the Johns Hopkins University in Baltimore have for the first time measured the rotation periods of stars i...

This principle – that the Sun is a star – was only proved in the 19th century when distances to the nearest stars were measured. It enables us to use the Sun, the only star we can observe in detail, to study processes occurring on other stars, and conversely, to use other stars to infer the past and future of our Sun. Stellar rotation periods are a key probe of magnetic phenomena on stars.

The AIP/JHU team worked on the four billion year-old open cluster M67, the only accessible cluster of solar-aged stars. They measured the tiny periodic light variations of twenty Sun-like stars caused by starspots on the stellar surfaces being carried across the disk during rotation. Since the examined stars are quite old their starspots are relatively small - similar to spots one can find on our Sun but tiny compared to those visible on younger stars. The measurements were only possible because of the exquisite sensitivity of the Kepler Space Telescope, now repurposed as the K2 mission.

Sydney Barnes, first author of the study, states: “We had predicted this would occur, but it has been a real privilege to have been able to actually make the measurements.” Co-author Jörg Weingrill adds: “With the measured rotational periods for stars up to the age of our Sun we can now confidently trace back the evolution of our home star.”

Scientific Publication: Sydney A. Barnes, Jörg Weingrill, Dario Fritzewski, Klaus G. Strassmeier, Imants Platais: „Rotation periods for cool stars in the 4 Gyr-old open cluster M67, the solar-stellar connection, and the applicability of gyrochronology to at least solar age“, The Astrophysical Journal, Volume 823, Nr. 1.

 

Caption: False-colour image of the stellar open cluster M67. Red, green, blue composite based on Johnson B, V and G bandpass images. Captured with WiFSIP/STELLA on Tenerife. (Credit:AIP)

 

Science Contact:
Dr. Sydney Barnes, +49 331 7499-379, sbarnes@aip.de
Dr. Jörg Weingrill, +49 331 7499-456, jweingrill@aip.de

Media Contact:
Kerstin Mork, +49 331 7499-803, presse@aip.de

 

The key topics of 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. Since 1992 the AIP is a member of the Leibniz Association.

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The centenary of astrophysicist Karl Schwarzschild's death

Karl Schwarzschild.

The centenary of astrophysicist Karl Schwarzschild's death

May 11th 1916 marks the death of Karl Schwarzschild, one of the most versatile astrophysicists and scientists of his time. He was only 42 years of age and at the height of his achievements when he...

Karl Schwarzschild was born in Frankfurt am Main, Germany, on October the 9th 1873. He started his career at the young age of 16, when he published papers on the determination of orbits of celestial bodies in Astronomical Notes. He studied in Strasbourg and obtained his doctoral degree in Munich in 1896. From 1897 he worked as an assistant at the Kuffner Observatory in Vienna and from 1901 to 1909, was a professor and director of the observatory in Göttingen. In 1908 Karl Schwarzschild was already recognized as one of the most accomplished astrophysicists of his time, and accepted the position as director of the Astrophysical Observatory Potsdam (AOP). AOP was founded in 1874 and was the first institute to have the word “astrophysics” in its name. Despite only spending eight years at AOP, Schwarzschild carried out fundamental work in astrophysics and advanced the general theory of relativity.

To this day, most books about him focus on the Schwarzschild solution to Einstein's field equations, but Schwarzschild's scientific interests were much broader. He worked intensely on celestial mechanics, stellar photometry, field theory, quantum mechanics and astronomical instrumentation. He also studied spectroscopy, stellar structure and stellar dynamics. Special appreciation should be paid to his theory of optical systems, which is still used when building large telescopes today.

Since 2011, in honour of Karl Schwarzschild, former director of the AOP, the Leibniz Institute of Astrophysics Potsdam (AIP) has been awarding young and promising natural scientists with the Karl Schwarzschild Fellowship.

Media Contact: Kerstin Mork, +49 331 7499-803, presse@aip.de

The key topics of 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. Since 1992 the AIP is a member of the Leibniz Association.

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Mercury crosses the Sun - Transit on 9 May 2016

Transit of Mercury. (Credit: AIP/J. Wendt)

Mercury crosses the Sun - Transit on 9 May 2016

2 May 2016. On the 9th of May at 1:12 p.m. local time, Mercury will begin its transit in front of the Sun – seen from the point of view of our Earth.

It will take more than seven hours for the planet to complete its path across the solar disc, and the transit will end at 8:40 p.m. The Leibniz Institute for Astrophysics Potsdam (AIP) is preparing for the scientific exploitation of this transit event: scientists want to detect sodium in Mercury’s exosphere and at the same time test the accuracy of their instruments for further studies. They will observe the Sun during the transit of Mercury with telescopes in Tenerife, in Arizona and at the solar observatory Einstein Tower in Potsdam. In addition, the AIP invites the public to its research campus in Potsdam-Babelsberg for public observations and talks about the transit of Mercury from 1–3 p.m.

 

 

Scientific Observations

With a diameter of only 4,878 kilometres, Mercury is the smallest planet of our solar system, and the closest one to the Sun.  Its gravitational force is too small to generate a stable atmosphere: only a very thin mixture of gas, called the exosphere, surrounds the planet. This exosphere mainly consists of oxygen, sodium and helium. It has such a low density that it is extremely hard to probe its structure. Only the rare transit events – like the upcoming one on the 9th of May – or space probes make such studies feasible. The last transit of Mercury that was visible from Central Europe occurred in 2003, the next such event will take place in 2019. AIP scientists therefore take this rare opportunity to observe the 2016 transit with various telescopes and instruments and from three different locations.

 

In Arizona: preparing for exoplanet studies

AIP scientist Matthias Mallonn will try to detect a signal of the exosphere of Mercury, using the PEPSI spectrograph coupled to the Solar-Disc Integrated Telescope (SDI) on the 3,200-meter high Mount Graham in Arizona. To do so, he will compare measurements of sodium absorption before, during and after the transit. This methodology, called transmission spectroscopy, is currently the most successful approach for studying the atmospheres of extrasolar planets. The exosphere of Mercury will reduce the intensity of solar light at the wavelength of sodium by a factor of only about one hundred thousand. This extremely small effect can only be detected with an extremely precise spectrograph: „We are taking data of the complete solar disc and therefore only obtain a very tiny signal of the exosphere of Mercury. I want to use these observations to assess the achievable precision of my method and to use this experience for later detections of exoplanet atmospheres”, Mallonn explained.

 

In Tenerife and in Potsdam: shape of the exosphere

Led by Carsten Denker, the solar physicists of AIP will focus observations on the detailed shape and the extension of the exosphere of Mercury. This was studied for the first time with the help of sodium absorption lines during a transit in 2003. Jointly with colleagues from Freiburg, Germany and from Spain, Denker now plans similar measurements during this transit of Mercury using a 2D spectrograph at the European GREGOR solar telescope in Tenerife and the team is hoping to also improve the accuracy of previous studies. In addition they use a high-speed camera and adaptive optics to achieve pin sharp images of the transit event. “The transit of Mercury is a unique chance for us to calibrate our instruments and methodology of observations”, Denker said. “Once we know how accurately we are able to distinguish between the sharp edge of the planet and the solar disc, we can also determine the general influence of stray-light on any observations with GREGOR.” If the weather permits, the astronomers also plan to point the mirror of the solar observatory Einstein Tower in Potsdam towards mercury, to study and document its transit across the Sun.

 

Public observations in Potsdam-Babelsberg: 1 to 3 p.m.

AIP invites all interested people to a public event that accompanies the transit of Mercury. The programme, at the research campus Potsdam-Babelsberg, includes talks (in German) and – if the skies are clear – public observation of the transit.

1p.m.: Observation of the start of the transit

1:30p.m: Talk by Dr. Axel Schwope: „Der Planet Merkur im Portrait“

2p.m: Talk by Dr. Matthias Mallonn „Der Merkurtransit als Generalprobe für die Erforschung erdähnlicher Planeten“

2:30p.m: Observation of the transit with the 50cm telescope

 

Media Contact:

Kerstin Mork, +49 331 7499-803, presse@aip.de


Science Contacts:

Dr. Matthias Mallonn, +49 331 7499-539, mmallonn@aip.de

Apl. Prof. Dr. Carsten Denker, +49 331-7499-297, cdenker@aip.de

 

The key topics of 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. Since 1992 the AIP is a member of the Leibniz Association.

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Cosmic Beacons Reveal the Milky Way's Ancient Core

The plane of our Galaxy as seen in infrared light from the WISE satellite. (Credit: NOAO/AURA/NSF/AIP/A. Kunder)

Cosmic Beacons Reveal the Milky Way's Ancient Core

22 April 2016. An international team of astronomers led by Dr. Andrea Kunder of the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany and Dr. R. Michael Rich of UCLA has discovered that t...

For the first time the team kinematically disentangled this ancient component from the stellar population that currently dominates the mass of the central Galaxy. The astronomers used the AAOmega spectrograph on the Anglo Australian Telescope near Siding Spring, Australia, and focussed on a well-known and ancient class of stars, called RR Lyrae variables. These stars pulsate in brightness roughly once a day, which make them more challenging to study than their static counterparts, but they have the advantage of being "standard candles". RR Lyrae stars allow exact distance estimations and are found only in stellar populations more than 10 billion years old, for example, in ancient halo globular clusters. The velocities of hundreds of stars were simultaneously recorded toward the constellation of Sagittarius over an area of the sky larger than the full moon. The team therefore was able to use the age stamp on the stars to explore the conditions in the central part of our Milky Way when it was formed.

Just as London and Paris are built on more ancient Roman or even older remains, our Milky Way galaxy also has multiple generations of stars that span the time from its formation to the present.  Since heavy elements, referred to by astronomers as “metals”, are brewed in stars, subsequent stellar generations become more and more metal-rich.  Therefore, the most ancient components of our Milky Way are expected to be metal-poor stars. Most of our Galaxy's central regions are dominated by metal-rich stars, meaning that they have approximately the same metal content as our Sun, and are arrayed in an American football-shaped structure called the "bar". These stars in the bar were found to orbit in roughly the same direction around the Galactic Centre. Hydrogen gas in the Milky Way also follows this rotation. Hence it was widely believed that all stars in the centre would rotate in this way. But to the astronomers’ astonishment, the RR Lyrae stars do not follow football-shaped orbits, but have large random motions more consistent with their having formed at a great distance from the centre of the Milky Way. "We expected to find that these stars rotate just like the rest of the bar" states lead investigator Kunder. Coauthor Juntai Shen of the Shanghai Astronomical Observatory adds, "They account for only one percent of the total mass of the bar, but this even more ancient population of stars appears to have a completely different origin than other stars there, consistent with having been one of the first parts of the Milky Way to form."

The RR Lyrae stars are moving targets - their pulsations result in changes in their apparent velocity over the course of a day. The team accounted for this, and was able to show that the velocity dispersion or random motion of the RR Lyrae star population was very high relative to the other stars in the Milky Way's center. The next steps will be to measure the exact metal content of the RR Lyrae population, which gives additional clues to the history of the stars, and enhance by three or four times the number of stars studied, that presently stands at almost 1000.

 

Scientific publication: Andrea Kunder et al.: Before the Bar: Kinematic Detection of A Spheroidal Metal-Poor Bulge Component, The Astrophysical Journal Letters, Volume 821, Number 2.
http://iopscience.iop.org/article/10.3847/2041-8205/821/2/L25/meta

 

Figure caption: The plane of our Galaxy as seen in infrared light from the WISE satellite.  The bulge is a distinct component in the central part of the Galaxy, and rotates cylindrically.  An ancient population, which does not exhibit cylindrical rotation, has been detected in the inner Milky Way. This population is estimated to be 1% of the mass of the bulge, and is likely to have been one of the first parts of the Milky Way to form. (Credit: NOAO/AURA/NSF/AIP/A. Kunder)

 

Science Contact: Dr. Andrea Kunder, +49 331 7499-646, akunder@aip.de
Media Contact: Kerstin Mork, +49 331 7499-803, presse@aip.de

The key topics of 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. Since 1992 the AIP is a member of the Leibniz Association.

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Third CALIFA data release: an inspiration to be curious about galaxies

11 April 2016. The Calar Alto Legacy Integral Field Area Survey (CALIFA) has released all of the data assembled over six years of work. The data of more than 600 galaxies are accessible for anyone ...

CALIFA provides a unique way to learn about the evolution of galaxies. While we ourselves live in a specific galaxy, there are many more siblings of the Milky Way out there. A favourite analogy of the project Principal Investigator, Dr. Sebastian Sanchez (UNAM, Mexiko): “A social scientist would naturally learn much more about a specific human by studying her environment, her family and other social relations. Exactly in the same way can we astronomers support the understanding of our cosmic home, the Milky Way, by studying its siblings in the skies. Studying galaxies to learn about their evolution is a fascinating subject, because - just as humans - they come in a wide variety of appearances shaped by their specific evolutionary histories.”

CALIFA is the first project to apply the technique of integral field spectroscopy to a sample that represents all galaxies in the Local Universe, providing a panoramic view of galaxy evolution. Integral field spectroscopy is a technique that allows to determine the properties of galaxies at many different places of each galaxy, i.e. in a spatially resolved way. The CALIFA sample on the other hand was specifically selected to be representative of galaxies in the Local Universe. “We knew that some galaxy properties change systematically. But seeing this in such detail and for so many properties for which this was previously not possible is new and exciting. It provides new avenues to study galaxies and understand why exactly they turn out to be as they are” says Dr. Jakob Walcher from the Leibniz Institute for Astrophysics Potsdam (AIP), the Project Scientist of CALIFA. Data were obtained with the AIP-built integral-field spectrograph PMAS/PPak at the Calar Alto Observatory.

“As a publicly funded project we see it as our duty to make the data available to the public. This also allows anyone interested to reproduce and work with our results” adds Dr. Stefano Zibetti (INAF Arcetri, Italy), Quality Control responsible of CALIFA, and therefore fundamentally involved in making sure that the data meet all quality criteria and will be truly useful to the international community of scientists. Ruben Garcia-Benito (IAA, Spain), responsible for running many of the fundamental software pieces that turned observations from the telescope into ready-to-release data adds: "We hope that the nice images we produce can inspire even more people to be curious about the Universe in general and galaxies in particular.”

Caption: The figure shows how galaxy properties vary systematically with their stellar mass (i.e. the number of stars they contain) and the star formation rate (i.e. the number of stars they are newly making every year at the present time). It illustrates the power of CALIFA data to help understand the evolution of galaxies.

Find the 3rd CALIFA data release online.

 

Science contact: Dr. Jakob Walcher, jwalcher@aip.de

Media contact: Kerstin Mork, +49 331 7499-803, presse@aip.de

 

The key topics of 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. Since 1992 the AIP is a member of the Leibniz Association.

Read more ...