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The secrets of dark energy

Large-Scale Structure of the Universe, observed with BOSS/SDSS-III (Credit: Daniel Eisenstein/SDSS-III).

The secrets of dark energy

14 July 2016. Astronomers announced this week the sharpest results yet on the properties of dark energy driving the accelerated expansion of the Universe. For their studies, scientists from the Ba...

BOSS measures the expansion rate of the Universe by determining the size of the baryonic acoustic oscillations (BAO) in the three-dimensional distribution of galaxies.  The original BAO size is determined by pressure waves that travelled through the young Universe up to when it was only 400,000 years old (the Universe is presently 13.8 billion years old), at which point they became frozen in the matter distribution of the Universe. The end result is that galaxies are preferentially separated by a characteristic distance, that astronomers call the acoustic scale.

The size of the acoustic scale at 13.8 billion years ago has been exquisitely determined from observations of the cosmic microwave background from the light emitted when the pressure waves became frozen.  Measuring the distribution of galaxies since that time allows astronomers to measure the acoustic scale at different times and to derive how dark matter and dark energy have competed to govern the rate of expansion of the Universe. Based on BOSS data, the acoustic scale has now been determined with an accuracy of less than one per cent from a point in time 7 billion years ago out to near the present day, two billion years ago.

Chia-Hsun Chuang, postdoctoral researcher at AIP, has contributed to this success by developing a new method to extract cosmological information from BOSS data. His approach jointly considers the cosmic microwave background and the observed three-dimensional galaxy distribution to derive cosmological parameters with minimum assumptions on dark energy. The method was applied to test different dark energy models and confirmed our current understanding of the expansion of the Universe to unprecedented accuracy.

In addition to studying the distribution of the galaxies themselves, AIP scientists Francisco-Shu Kitaura and Chia-Hsun Chuang for the first time also have had a closer look at the density minima in the BOSS data. These are the most quiet places in our Universe characterizing regions devoid of galaxies. By applying a similar analysis on these voids from the BOSS observations, the astronomers could determine the acoustic scale as the characteristic separation between the density minima.

The new BOSS galaxy map also reveals the distinctive signature of the coherent movement of galaxies toward regions of the Universe with more matter, due to the attractive force of gravity. Crucially, the observed amount of infall is explained well by the predictions of general relativity. This agreement supports the idea that the acceleration of the expansion rate is driven by a phenomenon at the largest cosmic scales, such as dark energy, rather than a breakdown of our gravitational theory.

 

Further information:

Science Contacts:

Dr. Chia-Hsun Chuang, +49 331 7499 639, achuang@aip.de
Dr. Francisco-Shu Kitaura, +49-331-7499 447, fkitaura@aip.de

Media Contact:
Dr. Gabriele Schönherr, +49 331-7499 804, presse@aip.de

 

Image:

This is one slice through the map of the large-scale structure of the Universe from the Sloan Digital Sky Survey and its Baryon Oscillation Spectroscopic Survey. Each dot in this picture indicates the position of a galaxy 6 billion years into the past. The image covers about 1/20th of the sky, a slice of the Universe 6 billion light-years wide, 4.5 billion light-years high, and 500 million light-years thick. Color indicates distance from Earth, ranging from yellow on the near side of the slice to purple on the far side. Galaxies are highly clustered, revealing superclusters and voids whose presence is seeded in the first fraction of a second after the Big Bang. This image contains 48,741 galaxies, about 3% of the full survey dataset. Grey patches are small regions without survey data.

Image credit: Daniel Eisenstein and SDSS-III.

 

About SDSS:

Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/.

SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS‑III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.

 

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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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Public presentation of Physics Student Awards

13 July 2016. On Thursday, July 14, starting at 5p.m. the Physikalische Gesellschaft zu Berlin invites to a public event in the Magnus-Haus in Berlin, where this year's Physics Student Awards wil...

Lisa Lehmann studied physics/astronomy at the University of Potsdam. In 2013 she picked an astrophysical topic for her Bachelor thesis about "Magnetic field measurements of eps Eridani", supervised at AIP, and published her results in a refereed journal later on. Her Master thesis addressed "Modeling Azimuthal Magnetic Field Bands on Cool Stars Using a Simple Model" under co-supervision of AIP and of the University of St. Andrews where she received a doctoral stipend afterwards.

The Physics Student Award of the Physikalische Gesellschaft zu Berlin (PGzB) was presented every year between 2004 and 2011, funded by the Wilhelm and Else Heraeus-Stiftung. Since 2013 the award is presented again, funded by the Siemens AG. The award ceremony is public.

 

Presentation of prizes 2016 (note: all talks in German)

Physikalische Gesellschaft zu Berlin e. V., Magnus-Haus, Am Kupfergraben 7, 10117 Berlin

Thursday, 14  July 2016, 5p.m. c.t.

Ceremonial address: Dr. Else Starkenburg, Leibniz Institute for Astrophysics Potsdam: Milky Way Archeology with Gaia

Awardees:

Theresa Höhne (TU Berlin)
Lisa Lehmann (U. Potsdam)
Sarah Loos (TU Berlin)
Pierre Volz (FU Berlin)
Alexander von Reppert (U. Potsdam)
Malte Wansleben (FU Berlin)
Sören Waßerroth (FU Berlin)
Berthold Wegner (HU Berlin)

More information: http://www.pgzb.tu-berlin.de/index.php?id=29

 

Media contact: Dr. Janine Fehlmeister, presse@aip.de, +49 331 7499 802

 

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IAU Symposium to take place in Potsdam

30. June 2016. At the 98th International Astronomical Union (IAU) Executive Committee meeting last May in Mexico the IAU Symposium 334 "Rediscovering our Galaxy" was approved to take place from the...

The aim of the IAU is to promote astronomy through international cooperation, and the key activity of the IAU is the organization of scientific meetings. Each year the IAU sponsors nine international IAU Symposia. In the last 25 years, only eight International IAU Symposia took place in Germany, with three of these (1992, 1993 and 2000) held in Potsdam. After 16 years, the IAU now returns to Germany with a symposium thanks to a successful application by AIP scientist Cristina Chiappini. The proposal was selected from more than 30 applications submitted for the coveted symposia.

The conference poster shows the Great Refractor, a historic telescope located in Potsdam, against the backdrop of a spectacular view of the Milky Way. "The poster communicates how new research on our Galaxy challenges conventional ideas on how it was formed," explains Cristina Chiappini, who also chairs the scientific organising team of the symposium. Marica Valentini, head of the local organizing committee adds: "We are honoured to have an IAU symposium in Potsdam for the first time since 2000."

The upcoming symposium confirms the leading role of the AIP in the research field of Galactic archaeology, i.e., the study of the motion and chemical composition of stars to uncover the history of our Milky Way.

Symposium website: https://iaus334.aip.de

 

Science contact: Dr. Cristina Chiappini, +49 331 7499-454, cristina.chiappini@aip.de

Media contact: Dr. Janine Fohlmeister, +49 331 7499-802, 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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Potsdam Astrophysical Summer School at AIP

20 June 2016. Today, the one-week summer school "Quantitative Spectroscopy in Astrophysics" begins at the Leibniz Institute for Astrophysics Potsdam (AIP). The school is targeted at graduate studen...

About 30 international participants will take part in an intense programme of lectures and practical exercises, given by experienced scientists from the AIP and the University of Potsdam. This year, the "Potsdam Astrophysical Summer School" is hosted by the Leibniz Graduate School for Quantitative Spectroscopy.

Spectroscopy is an essential and universal tool used in observational astrophysics, spanning topics from solar physics to cosmology. In recent years, enormous technological progress has been made in the field of spectroscopy, paving the way for a new generation of instruments capable of extremely high-resolution spatial and energy measurements. New instruments like the MUSE instrument at the Very Large Telescope (VLT) in Chile, to which AIP contributed, offer fantastic possibilities by coupling the discovery potential of an imaging device with the measuring capabilities of a spectrograph. Further, new technological developments include spectro-polarimeters, multi-object spectrographs, and fibre-fed spectrographs.

The Leibniz Graduate School for Quantitative Spectroscopy in Astrophysics is a collaborative project of the Leibniz Institute for Astrophysics Potsdam (AIP) and the Institute of Physics and Astronomy of the University of Potsdam (UP).

 

More Information:

 

Science contact: Apl. Prof. Dr. Carsten Denker, +49 331 7499-297, cdenker@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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New Master's programme in „Astrophysics“

The new Potsdam Astrophysics website (Source: www.astrophysik-potsdam.de)

New Master's programme in „Astrophysics“

9 June 2016. Starting in the winter semester 2016/2017, the University of Potsdam will offer students an Astrophysics master programme. The Deutsches Elektronen-Synchrotron DESY, the Leibniz Instit...

In Potsdam, students and researchers can take advantage of a unique and broad range of astrophysical topics. Furthermore, Astrophysics research being carried out at the University of Potsdam stands out due to strong networks with non-university research institutions specializing in astrophysical topics. These three internationally leading institutions make Potsdam one of the major sites of astrophysical research in Germany. Joint professorships, associate and honorary professorships and joint research groups strengthen academic teaching at the University. An overarching structured doctoral training and joint graduate schools provide an excellent environment to PhD students.

 

The University of Potsdam and the non-university partner institutions have also used the start of the new Master’s program as an opportunity to initiate a new Astrophysics website: The manifold of activities and their close collaboration in research and education is now online in the common framework of the ”Astrophysics Network Potsdam“.

 

In addition to a wealth of information for students and researchers at all stages of their careers, the new website also contains insights into some personal impressions and experiences of Potsdam’s scientists: on their scientific discoveries, on the Potsdam student and researcher life and on observation campaigns in remote locations such as Chile or even the Antarctic.

 

„When any prospective student or young researcher visits the website, we want her or him to recognize immediately the unique study and career opportunities that our strong network offers here in Potsdam.“ said Philipp Richter, professor at the University of Potsdam and one of the initiators of the new website.

 

More information:

 

Contact person (also for the Master’s programme):

Professor Dr. Philipp Richter, Email: prichter@astro.uni-potsdam.de, Phone: +49 331 977-1841

 

Contact persons for journalists:

  • Deutsches Elektronen-Synchrotron, Zeuthen: Ulrike Behrens, Email: ulrike.behrens@desy.de, Phone: +49 33762 7-7201
  • Leibniz Institute for Astrophysics Potsdam: Dr. Janine Fohlmeister, Email: presse@aip.de, Phone: +49 331 7499-802
  • Max Planck Institute for Gravitational Physics: Dr. Elke Müller, Email: elke.mueller@aei.mpg.de, Phone: +49 331 567-7303
  • University of Potsdam, Faculty of Science: Dr. Barbara Eckardt, Email: eckardt@uni-potsdam.de, Phone: +49 331 977-2964
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