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Hofreiter Anton Dissertation Defense

PhD defense Tomas Stolker - protoplanetary disks and exoplanets in scattered light

30 August 2017

On September 7, 2017, Tomas Stolker will defend his PhD thesis "Protoplanetary disks and exoplanets in scattered light".


High-contrast imaging facilitates the direct detection of protoplanetary disks in scattered light and self-luminous exoplanets on long-period orbits. The combined power of extreme adaptive optics and differential imaging techniques delivers high spatial resolution images of disk morphologies down to several astronomical units from the star. The distribution of the small dust grains in the disk surface provides important clues about the processes that drive disk evolution and the shaping effects of embedded planets on their circumstellar environment. The scattered light is also imprinted by the properties of the dust particles through their color and angle of scattering.

In this thesis, a new scattering radiative transfer code for exoplanet atmospheres is presented which is used to predict the polarization signal from young gas giants with atmospheric cloud variations and circumplanetary disks. Furthermore, four protoplanetary disks are studied in scattered light with the SPHERE instrument at the Very Large Telescope. Intriguing substructures and brightness asymmetries are revealed in all disks including shadows, spiral arms, gaps and cavities. The structure and dynamics of the innermost disk regions are investigated with shadows that are cast on the outer disk while the detected spiral arms, gaps and cavities are used as tracers for embedded planets. The disk structure and dust properties are quantified with three-dimensional radiative transfer simulations. Additionally, a numerical method is developed that allows for a more precise determination of the scattering phase function of the dust by considering the geometry of the disk surface.

PhD defense page

Published by  Anton Pannekoek Institute for Astronomy

Anton "Toni" Hofreiter (born 2 February 1970 in Munich) is a German biologist and politician.

Political career[edit]

As a member of Alliance '90/The Greens, Hofreiter has been a member of the Bundestag since the 2005 elections. Between 2005 and 2013, he served as member of the Committee on Transport, Building and Urban Development; he served as chairman of the committee from 2011 until 2013. He was also member of the German-Austrian Parliamentary Friendship Group.

Hofreiter has been co-chair of the Green Party's parliamentary group, together with Katrin Göring-Eckardt, since October 2013.[1] He was elected unopposed as the sole candidate of the group’s left faction.[2]

Political positions[edit]

Human rights[edit]

Following 2012 reports by Spiegel Online according to which a luxury Boeing 767 belonging to Belarusian PresidentAlexander Lukashenko was refitted by Lufthansa Technik in Hamburg with expensive accoutrement to further accommodate the dictator's expensive tastes, Hofreiter criticized the company for cooperating with a "dictator who gives orders for the death penalty and violently destroys the opposition."[3]

In January 2015, Hofreiter criticized a decision by police in the eastern city of Dresden to ban an anti-Islam march after death threats toward an organizer, slamming the move as a worrying restriction on freedom of speech.[4] In the ongoing european migration crisis 2015 Hofreiter is an outspoken proponent of a liberal migration policy.[5]

European integration[edit]

In a 2014 debate on a reform of the voting rules in the Governing Council of the European Central Bank, Hofreiter strongly criticized calls for a power of veto. "Bundesbank chief Jens Weidmann is not Germany's vicegerent in the ECB Council," he told the Frankfurter Allgemeine Zeitung.[6]

Other activities[edit]

  • Denkwerk Demokratie, Member of the Advisory Board


  1. ^Christina Hebel, Christoph Sydow: Fraktionsspitze: Göring-Eckardt gewinnt Kampfabstimmung bei Grünen. In: Spiegel Online, 8. Oktober 2013.
  2. ^Quentin Peel (October 8, 2013), Germany Greens set to test waters for possible CDU coalitionFinancial Times.
  3. ^Quentin Peel (October 8, 2013), [1]Radio Free Europe/Radio Liberty, November 12, 2012.
  4. ^Harriet Torry and Anton Troianovski (January 19, 2015), Seeing in Crisis the Last Best Chance to Unite EuropeWall Street Journal.
  5. ^http://www.stern.de/politik/deutschland/fluechtlingskrise--bund-und-laender-einigen-sich-auf-kostenverteilung-6467130.html
  6. ^ECB voting rights ‘rotation’ raises fears in GermanyEurActiv, June 19, 2014.

External links[edit]

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