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Epsilon Aurigae - an extremely dynamic binary star

Artist's impression of Epsilon Aurigae. Image credit: NASA/JPL-Caltech.

Epsilon Aurigae - an extremely dynamic binary star

12 November 2014. Based on an observation campaign lasting seven years, scientists from the Leibniz Institute for Astrophysics Potsdam (AIP) published new findings about the binary star system Epsi...

Epsilon Aurigae is a bright supergiant with a diameter 300 times greater than that of the Sun; its mass is 25 times greater. Its mysterious companion star is concealed in a disk, and cannot be observed directly. Thanks to their observations, Potsdam’s astronomers were able to show that the main star pulsates non-radially, rotates very quickly and loses mass to its invisible companion, whose accretion disk also rotates.

The binary star system must be extremely dynamic for the mass to be able to flow, as proven, from the supergiant towards the disk of the invisible companion star. The astronomers determined that the giant star rotates comparatively quickly, with a period of only 540 days. In interaction with its non-radial pulsation, which has also been observed, this could be the cause of intensified mass transfer between the two stars.

“I would not like to get too close to Epsilon Aurigae with my spacecraft,” stated Professor Klaus Strassmeier, leader of the study and Research Branch Director at AIP. “What we see here is a system whose two very massive stars are simultaneously involved in all of the turbulent scenarios of stellar evolution.”

Determining the companion star in further detail remains an exciting task. In fact, the data also shows that the disk of the companion star is not extended in a circular, but in a “pear-shaped” fashion in the opposite direction to the orbital motion. Consequently, it is not possible to determine the mass of the star directly, as is the case for circular disks derived from Kepler’s laws.

Potsdam’s astronomers have been interested for a long time in Epsilon Aurigae, some 3,000 light years away in the northern sky. As early as in 1903, Hans Ludendorff and Hermann Vogel carried out the first photometric and spectroscopic observations of the star at Potsdam, and discovered that it was an eclipsing binary star with a 27-year period – the longest eclipsing period that has ever been measured.

The huge quantities of data obtained using the STELLA telescope are made available to the astronomical community for further analysis.

The study "Time-series high-resolution spectroscopy and photometry of ε Aurigae from 2006–2013: Another brick in the wall" was published in November in Astronomical Notes, Vol. 335, issue 9.

 

 

Science contact: Professor Dr. Klaus G. Strassmeier, kstrassmeier@aip.de

Media contact: Kerstin Mork, presse@aip.de, 0331-7499 469

 

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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Partial solar eclipse observed by SDI

SDI image of a partial solar eclipse on 23 October.

Partial solar eclipse observed by SDI

23 October 2014. The images show a large Sunspot that appeared two days earlier. The SDI telescope uses the Sun as a guide star to keep its image to be well-projected onto the entrance fibres to th...

PEPSI is a high-resolution echelle spectrograph recently installed on the 2x8.4m Large Binocular Telescope (LBT) on Mt.Graham in Arizona and designed to obtain spectra in integral light from the Nasmyth focal station or polarized spectra with polarimeters located at the Gregorian focus of the telescope.

As an additional functionality, PEPSI uses a small 1cm binocular Solar telescope located outside the LBT in order to feed the spectrograph with the solar disk integrated (SDI) light with a resolving power of 270 000 over the whole optical spectral range. The purpose of this instrument is to take high signal-to-noise Solar spectra continuously on every day basis over the whole solar cycle to study the pressure and gravity modes of solar pulsations in high resolution, as well as, long term line profile variation over solar cycle.

 

 


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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 An unprecedented view of two hundred galaxies

A panoramic view of the properties of galaxies.

An unprecedented view of two hundred galaxies

1 October 2014. The second data release of the international project CALIFA - a survey of galaxies carried out at Calar Alto observatory – will take place today. Galaxies are the result of an evo...

“The data corresponding to the hundred galaxies included in the first data release of November 2012 have already been downloaded more than seven thousand times and they have produced a wide variety of results, both from inside and outside the CALIFA collaboration" underlines Sebastián Sánchez, principal investigator of the project. "With more than thirty peer review publications, more than hundred contributions to scientific meetings and five PhD theses submitted, this project is the most productive among those ever carried out at Calar Alto. This data release is a new milestone of the project, which already can be considered an international reference in the field of extragalactic surveys”.

The CALIFA Project allows not only to inspect the galaxies in detail, but it also provides with data on the evolution of each particular galaxy with time.

Thanks to the CALIFA data, the astronomers have been able to deduce the history of the mass, luminosity and chemical evolution of the CALIFA sample of galaxies, and thus they have found that more massive galaxies grow faster than less massive ones, and that they form their central regions before the external ones (inside-out mass assembly). CALIFA has also shed light on how chemical elements needed for file are produced within the galaxies or on the physical processes involved on galactic collisions, and it has even observed the last generation of stars still in their birth cocoon.

The above picture shows:  1) broad band images (center up), 2) stellar mass surface densities (upper right), 3) average stellar ages (lower right), 4) diagnostic emission lines (lower center), 5) Halpha emission (lower left) and 6) kinematics (upper left). (Credits: R. Garcia-Benito, F. Rosales-Ortega, E. Pérez, C. J. Walcher, S. F. Sanchez and the CALIFA team)

Science contact: Dr. Jakob Walcher, +49 331-7499 243, jwalcher@aip.de
Media contact: Kerstin Mork , +49 331-7499 469, 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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Matthias Steinmetz elected President of the German Astronomical Society

Professor Matthias Steinmetz.

Matthias Steinmetz elected President of the German Astronomical Society

24 September 2014. Prof. Dr. Matthias Steinmetz, scientific chairman of the Leibniz Institute for Astrophysics Potsdam (AIP), is the new President of the German Astronomical Society (Astronomische ...

Matthias Steinmetz studied mathematics and physics in Saarbrücken and at the Technical University Munich. He received his doctorate in physics in Munich in 1993 and initially worked at the Max Planck Institute for Astrophysics in Garching. In 1996, aged 30, Matthias Steinmetz accepted a faculty position at the University of Arizona in Tucson. In 2002, he was appointed director of the AIP and professor at the University of Potsdam. Steinmetz was also visiting researcher at the University of California at Santa Barbara and Berkeley. His area of expertise is computational astrophysics and cosmology. Matthias Steinmetz has successfully engaged in particle hydrodynamics simulations of cosmological environments as well as in simulations of dark matter in the Galactic halo. Large surveys of the Milky Way, which are associated with his name, enabled new findings regarding the field of the galactic dynamics and the properties of kinematical groups of stars. He is also German speaker of the International Astronomical Union and advisor and member of several committees within the scientific community.

 

Prof. Dr. Joachim Wambsganß, Director of the Zentrum für Astronomie der Universität Heidelberg, has been elected vice president.

 

The German Astronomical Society, founded in 1863, is a modern astronomical society with more than 800 members dedicated to the advancement of astronomy and astrophysics and the networking between astronomers. It represents German astronomers, organises scientific meetings, publishes journals, offers grants, recognises outstanding work through awards and places a high priority on the support of talented young scientists, public outreach and astronomy education in schools.

(Press release of the German Astronomical Society)

 

Media Contact AG: Dr. Klaus Jäger, +49 6221 – 528 379, jaeger@mpia.de

Media Contact AIP: Kerstin Mork, +49 331 7499 469, 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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Astronomers unveil secrets of giant elliptical galaxies

Velocity map of M87.

Astronomers unveil secrets of giant elliptical galaxies

12 September 2014 Davor Krajnović, astronomer at the Leibniz Institute for Astrophysics Potsdam (AIP), and his colleagues Eric Emsellem (ESO) and Marc Sarzi (University of Hertfordshire), have dis...

The three astronomers observed the giant galaxy M87 (NGC4486), which is the central galaxy in the Virgo cluster, and discovered that it displays some bulk rotation, albeit of a very low amplitude. The precision of MUSE allowed the team to reveal that the stars of M87 can move around its centre with average velocities of just 10-20 km/s. Equivalent to 36-72,000 km/h, this speed may seem very high, but for galaxies this is extremely slow.

Elliptical galaxies have long been considered as essentially being made up of old stars that move randomly within them, like a swarm of bees. This has been challenged in many instances in the past ten-twenty years, but giant elliptical galaxies are still considered as a nearly round and non-rotating group of old stars.

By showing that a "simple" galaxy like M87 can be quite complicated in the eyes of the new MUSE spectrograph, this result demonstrates the potential of this new instrument for further advancing our understanding of galaxies, and their formation. Davor Krajnović states: “MUSE has the capability to enhance our understanding of galaxies, how they form and develop. By using the MUSE velocity data to constrain simulation models, we might reach a whole new level of precision.” Their work is published in the Monthly Notices of the Royal Astronomical Society and a pre-publication version of the paper is available on arXiv: http://arxiv.org/abs/1408.6844.

The Multi Unit Spectroscopic Explorer (MUSE) is a 3D-spectrograph for the Very Large Telescope (VLT) of the European Southern Observatory at Paranal (Chile). MUSE features a complex optical system with the capacity to split and slice a field that measures one square arcminute on the sky into 90,000 spatial elements. For each point a spectrum is created, covering the optical and near infrared wavelength region of 465-930nm. AIP provides the Data Reduction Software and operates one of the data centres accessible to scientists from all over the world.

 

(Click to enlarge)

Left: Image of M87: Some small companions galaxies of this giant and round elliptical galaxy are visible to the right of the image. The red square delineates the field-of-view of the MUSE instrument, where the velocity of the central stars of M87 have been measured.

Right: A map for the average velocity of the stars in the central region of M87, divided in polygonal regions where the MUSE data have been combined to reach a sufficient quality for these measurements. After accounting that M87 as a whole is moving away from us, red or yellow bins show stars that on average are receding whereas blue or light azure bins show stars that on average are approaching. The MUSE map reveal a complex motion of the stars in M87, where stars move in one way in the central region and in another in its outskirts.

 

Further information:

 

Science contact: Dr. Davor Krajnović, +49 331-7499 237, dkrajnovic@aip.de

Media contact: Kerstin Mork , +49 331-7499 469, 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 ...