Abschlussarbeiten

Aktuelle Arbeiten

Doktorarbeiten

• Stefanie Gebauer: Atmospheric evolution of terrestrial exoplanets
  How Earth evolved to be habitable is a central question to understanding our own origins and our place in the Universe. Addressing this question requires knowledge of the complex interplay between many processes - physical, chemical, biological and geological - acting over a vast range of temporal and spatial scales. Also, in terms of exoplanet studies, many stars in our solar neighbourhood are young, so any rocky planets they may have are also likely to be young – this is an important motivation for studying the Early Earth’s atmosphere as a reference to compare with such worlds.
  To investigate these issues, our goal is to apply a global mean column model with interactive oxygen (O2), carbon dioxide (CO2) and nitrogen (N2) chemistry, coupled radiative transfer and including biogeochemical cycles. We will focus on specific points in time (“snapshots”), such as before, at and after the so-called Great Rise in Oxygen (GOE) which took place around 2.3 Ga (gigayears) ago. Each snapshot can also be interpreted as the atmosphere of a hypothetical extrasolar terrestrial planet, which could be found in the near future by space missions like CoRoT and Kepler.
  
  
• Alexander Hölscher: Evaluation of Cometary Gas Production Rates
  The goal of this thesis is to investigate and extend if possible the current classification of comets based on their chemical composition. This classification is based on the abundances of the radicals CN, C2, C3, NH2, OH etc. in the coma.
  Since these radicals dissociate from larger parent species the goal is to establish a classification with the parent species. These parent species can be observed in the IR and radio wavelength range. But the radicals can be observed in the UV, even for fainter comets. This is important to gain a significant amount of measurements for statistical investigations.
  The focus of our work is to investigate the link between the C2 and the C3 radicals and possible parent species. For this purpose a 1D-model of the cometary coma is applied, which was developed in our working group and which is to be upgraded. Additionally an expansion of the data set of production rates of the radicals C2, C3 in the existing database can give constraints on the role of possible C2 and C3 parent species like C2H2.
  
  
•  Daniel Kitzmann: Formation and evolution of clouds in atmospheres of terrestrial extrasolar planets
  The climate of terrestrial planets results from the energy balance between absorbed stellar radiation and the loss of thermal radiation emitted from the surface and the atmosphere to space. Cloud particles can have a strong impact on the radiation budget in terrestrial planetary atmospheres and, therefore, also on the planetary climate and the position and the extension of habitable zones around different central stars. They can reflect the stellar radiation back towards space, thereby reducing the stellar energy available for heating the surface (albedo effect), but on the other hand also reduce the loss of thermal radiation to space (greenhouse effect). The effectiveness of the albedo and the greenhouse effect depend on the strongly wavelength dependent optical properties of the clouds in combination with the spectral distribution of the incident stellar and atmospheric thermal radiation. The absorption and scattering characteristics of the cloud particles, on the other hand, are determined by their microphysical properties, such as size distribution and shape.
  The aim of this thesis is to study the formation and properties of clouds in atmospheres of terrestrial extrasolar planets and their effect on the planetary climate. Special focus is placed on CO2 clouds which are important for the determination of the outer boundary of the habitable zone. 
  
  
•  Thomas Pasternacki: Homogeneous study of the CoRoT-planets
  In exoplanetary science it is essential to determine the planetary parameters with the highest possible precision. These parameters are important for our understanding of the nature of the exoplanets and serve as input parameters for the scientific studies which follow.
  The French satellite mission CoRoT delivers qualitative high photometric signals of around 100,000 stars and has lead to 17 confirmed planets up to now. The evaluation of the data for these planets has, until now been mostly achieved using a rather non-homogeneous setup in terms of staff, software versions, expertise etc.
  Therefore, a homogeneous study of all currently known CoRoT planets is desirable. Such a study should ideally be performed by one software in the most possible homogeneous way including all knowledge, e. g., gained during evaluation of the confirmed planets, and new aspects such as improved handling of limb darkening, binning and reflection effects. Another outcome of studying the transit events of a planet is the measurement of a possible transit timing variation. These variations can provide hints for other companions in the examined system.

Masterarbeiten

• Fachreddin Tabataba-Vakili: Modelling the Influence of Cosmic Rays on the atmospheric chemistry of Earth-like exoplanets

Bachelorarbeiten

• Stephan Breitner: Evaluierung möglicher Beobachtungsszenarien für die geplante ESA-Mission PLATO
  In dieser Arbeit wird für die Satellitenmission PLATO, die vom Lagrangepunkt L2 aus mit der Transitmethode nach extrasolaren Planeten suchen soll, eine Reihe möglicher Beobachtungsstrategien bzgl. der voraussichtlich entdeckten Planeten verglichen. Dabei wird sowohl die Anzahl der Planeten als auch deren Umlaufdauer berücksichtigt. Es geht vor allem darum herauszufinden, wie viele Felder man untersuchen sollte, um den für diese Arbeit leicht modifizierten Anforderungen der Mission am besten zu entsprechen.
  
  
• Martin Gärtner: Numerische Modellierung von TTVs extrasolarer Planetensysteme am Beispiel ausgewählter CoRoT-Systeme
  Ob und in welchem Zeitraum es möglich ist, die TTVs eines beliebigen extrasolaren Planetensystems mit heutigen Mitteln zu messen, ist nicht immer leicht zu beantworten. Dafür wird in dieser Arbeit ein Programm geschrieben, das nach Eingabe der für das Planetensystem wichtigen Parameter, die zeitlichen Variationen in der Transitzeit und den orbitalen Parametern grafisch darstellt. Dabei wird besonderen Wert darauf gelegt, dass nicht nur Spezialfälle, sondern sämtliche Konstellationen von Planetensystemen betrachtet werden können, was in dieser Form vorher nicht möglich war. Im speziellen wird in dieser Arbeit das Programm auf die beiden Mehrplanetensysteme CoRoT-7 und CoRoT-24 angewandt.

Abgeschlossene Arbeiten

Doktorarbeiten

• Thomas Fruth (2013): Search for Planetary Transits and Stellar Variability with BESTII and ASTEP
• Joachim Stock (2013): Chemical Pathway Analysis of the Martian Atmosphere
• Mareike Godolt (2012):  3D Climate Modeling of Earth-like Extrasolar Planets Orbiting  Different Types of Central Stars
• Barbara Stracke (2012): Modeling of terrestrial extrasolar planetary atmospheres in view of  habitability
• Philip von Paris (2010): The atmospheres of Super-Earths
• Petr Kabath (2009): Characterization of the stellar variability in CoRoT fields with BEST telescopes
• Pascal Hedelt (2009): Radiative transfer in the exosphere of Saturn's moon Titan
• Michael Weiler (2007): Study of the Gas and Dust Activity of Recent Comets
• Holger Voß (2006): Developing a ground-based search system for transits of extrasolar planets

Diplomarbeiten

• Arik Rohloff (2012): Die Auswirkung hochenergetischer Strahlung auf CH4, N2O, und O3 in der Atmosphäre von Planeten in der habitablen Zone
• Falk Dambowsky (2011): Modellierung heißer Atmosphären terrestrischer Exoplaneten
• Stefan Linz (2011): Neuanalyse von Mehrfarbenphotometrie planetarer Transits
• André Bathke (2011): Modellierung von Lichtkurven bedeckungsveränderlicher Sterne in Bildfeldern von BEST und BEST II
• Karol Palczynski (2010): Analyse photochemischer Reaktionswege in erdähnlichen Planetenatmosphären
• Melanie Schulze (2010): Photometrische Datenauswertung zur Suche nach variablen Sternen und Transits extrasolarer Planeten im BEST-Datensatz F15
• Martin Günther (2009): Investigations of methods for the detection of exoplanetary transits
• Thomas Pasternacki (2009): Optimierte photometrische Datenauswertung zur Suche variabler Sterne und Planetentransits in BEST-Daten
• Thomas Fruth (2008): Perspektiven fü die Transitsuche: Vergleich des Standortes Dome C (Antarktis) mit Standorten gemäßigter Breite
• Tino Wiese (2007): Analyse stellarer Lichtkurven zur Suche nach Transits extrasolarer Planeten
• Philip von Paris (2006): Modellierung CO2-dominierter Atmosphären terrestrischer Planeten
• Pascal Hedelt (2006): Transitspektroskopie extrasolarer Planeten am Beispiel des Venustransits

Masterarbeiten

• Antonio Pilello (2010): Photometric data reduction and variability characterisation of BEST target field F8

Bachelorarbeiten

• Maximilian Stilz (2012): Transit Timing Variation with BEST II´
• Pirmin Kustin (2012): Charakterisierung des korrelierten Rauschens  in CoRoT- und BEST II-Daten
• Andre Röhm (2012): Untersuchung von N2O als  potentielle Biosignatur in terrestrischen Exoplaneten
• Fachreddin Tabataba-Vakili (2011): Effects of Cosmic Rays on Trace Gases in Earth-Like Atmospheres
• Sabrina Kirste (2008): Prospects for Transit Timing Analysis of Extrasolar Planets