Björn S. Konrad

PhD Candidate in Astrophysics,
Exoplanets & Habitabillity Group
ETH Zürich

In my research, I focus on atmospheric retrieval studies for terrestrial exoplanets. I am highly interested in understanding how well we can constrain the surface conditions and atmospheric properties of terrestrial exoplanets by analyzing their spectra. I am particularly interested in the Mid-Infrared thermal emission of these planets, since it provides an exclusive probe to several potential biosignature gases. You can find an Introduction to my latest Research topics here.

You can find lists of my publications and conference abstracts on ADS or on ORCiD.

Selected Research Projects

Following, I list some of my recent research projects. You can find a full list of my publications on ADS.

Characterizing Earth in the Mid-Infrared from an Observer’s Perspective

Mettler & Konrad et al. (2023) | Poster Life in the Universe II 2023

We study a set of real disk-integrated MIR thermal emission spectra of Earth. We consider monthly flux averages for January and July as well as three viewing angles: North Pole, South Pole, and Equatorial Combined. We simulate observations of Earth with the Large Interferometer For Exoplanets (LIFE) using LIFEsim (Dannert et al. 2022), by putting Earth on a 1 AU orbit around a G2V star located 10 pc from the observer. We generate spectra for different combinations of noise (S/N = 10, 20) and spectral resolution (R = 50, 100). Retrievals on such Earth remote sensing data help us understand how exoplanet observations can be safely analyzed. By treating Earth as an exoplanet, we study how our characterization depends on the observed viewing angle or season. We also investigate if retrievals that use simple 1D forward models can correctly characterize atmospheres. Finally, we study how patchy clouds can affect our characterization.

Venus-Twin Retrievals for LIFE

Konrad et al. (2023) | Poster Exoplanets IV 2022 | Talk EPSC 2021

Similar to the Earth-twin, we run retrievals for mock observations of a Venus-twin with LIFE. To accurately model Venus’ MIR spectrum, the sulfuric acid (H2SO4) clouds must be taken into account. We use LIFEsim (Dannert et al. (2022)) to generate the mock observations of a Venus-twin at 10 pc. By running retrievals assuming a cloudfree or cloudy atmosphere, we investigate how the quality of a spectrum and clouds impact retrieval results. We studied how clouds impact retrievals, if clouds are detectable in the MIR, and if the R and S/N found in the Earth-twin retrieval study are sufficient to characterize a Venus-twin.

Venus-Twin Results

Our results for planet parameters and atmospheric gas abundances do not depend on the spectral quality. This is true for both retrievals using the cloud-free and cloudy models. We manage to constrain Venus' radius, Bond albedo, and atmospheric CO2 abundance. However, due to the opaque cloud layer, we can not constrain the surface temperature and pressure.
Since both models fit the observation well, we test if the cloudy model is preferred by our retrieval via the Bayes’ factor. In the figure to the left, we plot the Bayes’ factor for different input qualities. We identify two regimes:

  1. Low quality spectra: Both models fit equally well. The cloud-free model is preferred, because it has less parameters. The information content of these spectra is too low to justify the additional parameters of the cloudy model. Thus, we cannot infer clouds.
  2. High quality spectra: The cloudy model fits better. Thus, we can infer clouds.

Earth-Twin Retrievals for LIFE

Konrad et al. (2022) | Poster Latsis Symposium 2022 | Poster Exoplanets IV 2022 | Talk EPSC 2020

We run Bayesian atmospheric retrievals for mock observations with LIFE of the midinfrared (MIR) thermal emission spectrum of a cloud-free Earth-twin exoplanet at 10 pc. The mock observations are generated with LIFEsim (Dannert et al. 2022), which accounts for all major astrophysical noise sources. We investigate how well we can constrain the atmospheric properties of an Earth-twin in retrievals of spectra of different quality. The quality of a spectrum depends on the Spectral resolution (R), the LIFEsim noise level (S/N), and the Wavelength coverage.

Earth-Twin Results

Independent of the spectral quality, the planet's radius, surface temperature, and surface pressure are constrainable via MIR LIFE observations. The abundances of Earth’s main atmospheric gases N2 and O2 are not retrieved due to a lack of MIR features. However, we can infer the presence of a ≈ 1 bar atmosphere, of which the bulk is transparent in the MIR. For trace gases (see Figure on the left side), we observe the following:

  1. For most gases our results show no strong dependence on the spectral quality.
  2. For CH4 our results improve significantly with increasing spectral quality.
A more detailed analysis of our results reveals that an R of at least 50 and an S/N of at least 10 is required to detect CH4 in the atmosphere of an Earth-twin exoplanet.

Curriculum Vitae

Below you can find selected elements from my curriculum, which are relevant to my scientific career. You can find my full CV here.

Professional Experience

ETH Doc.Mobility Fellow at Harvard University

09/2023 - Current, Harvard University, Cambridge MA, United States

  • Main Research Focus: Characterization of terrestrial (exo-)planets with atmospheric retrievals.
  • Supervisor: Prof. Sascha P. Quanz

Doctoral Researcher ETH

12/2020 - Current, ETH (Swiss Federal Institute of Technology), Zürich, Switzerland

  • Main Research Focus: Characterization of terrestrial (exo-)planets with atmospheric retrievals.
  • Supervisor: Prof. Sascha P. Quanz

PVK Assistant VMP ETH

12/2020 - Current, VMP (Association of physics and mathematics students at ETH), Zürich, Switzerland

  • Task: Host exam preparation courses for first-year physics and mathematics students at ETH Zürich.
  • Courses: Physics II (D-PHYS/D-MATH; springs 2022, 2021), Physics I (D-PHYS/D-MATH; falls 2020, 2021)

Teaching Assistant ETH

09/2019 - Current, ETH (Swiss Federal Institute of Technology), Zürich, Switzerland

  • Task: Host exercise classes for students accompanying the lectures at ETH Zürich.
  • Courses: Physics Lab II (D-PHYS; spring 2022), Astronomy (D-PHYS/D-MATH; fall 2021), Physics I (D-USYS; spring 2021), Physics I (D-MATL; spring 2020), Physics I (D-CHAB; falls 2019,2022), Physics II (D-CHAB; spring 2023)

Education

Doctor of Sciences ETH

12/2020 - Current, ETH (Swiss Federal Institute of Technology), Zürich, Switzerland

  • Main Research Focus: Characterization of Terrestrial (Exo-)Planets with Atmospheric Retrievals.
  • Supervisor: Prof. Sascha P. Quanz

Master of Science ETH in Physics, with distinction

09/2018 - 08/2020, ETH (Swiss Federal Institute of Technology), Zürich, Switzerland

  • Focus: Astrophysics & Cosmology
  • Master’s Thesis: Supervised by Dr. Eleonora Alei and Prof. Sascha P. Quanz.
    (Honoured with the ETH Silver medal for outstanding Master's theses 2021)
    "Atmospheric Retrieval Sensitivity Analysis for Earth-Twin Exoplanets."
  • Semester Project: Supervised by Dr. Anna L. Boehle and Prof. Sascha P. Quanz.
    "Cryogenic Characterization of the Grating-Vector APP for the ERIS Instrument at the VLT."

Bachelor of Science ETH in Physics

09/2014 – 09/2017, ETH (Swiss Federal Institute of Technology), Zürich, Switzerland

  • Semester Project: Supervised by Dr. Sebastian Daemgen and Prof. Hans Martin Schmid.
    "Simulation of Planet and Brown Dwarf Detection Probability in Binary Systems for Direct Imaging."

Contact Me