Kim Angelique Kahle

For an overview poster, click here. In recent decades, more than 5000 extrasolar planets have been discovered orbiting the stars of the night sky. Among these typically short orbital period planets, sub-Neptunes are the most abundant class, with roughly between 2 and 3.5 earth radii. Interestingly, these common objects have no analog in the solar system, making them attractive targets for exoplanet research. A tool for studying the composition and conditions on exoplanets is transmission spectroscopy, which analyzes the spectrum of the starlight that is filtered through the planet's atmosphere. This technique requires observations with high sensitivity, as the transiting planets cover only a small fraction of their host star. While currently operating facilities are well suited for observing giant planets, observing the smaller sub-Neptunes is more challenging and has therefore only been done for very few of them. Many of the published sub-Neptune spectra are either featureless or show muted spectral features, possibly due to high mean molecular weight atmospheres or alternatively high altitude hazes or clouds. The Sub-neptune Planetary Atmosphere Characterization Experiment (SPACE) with the Hubble Space Telescope will systematically investigate the reason behind these findings. For this, we observe and analyze the transmission spectra of 8 sub-Neptunes that span a diverse sample in radius (2.2-3.4 earth radii) and temperature (320K-1300K), together with UV spectra of their host stars. With these new observations, we will establish demographic trends among cloudy and cloud-free sub-Neptunes which can be used to distinguish between the possible feature attenuation scenarios. The detected spectral features will inform us about the chemical processes and dominant molecular species in the atmospheres, providing a starting point for exploring the wide range of atmospheric compositions predicted by formation models.

The hot Jupiter WASP-121b has been studied in detail in the past years with both, space- and ground-based telecopes. Its size and equilibrium temperature make it an excellent natural laboratory to learn about physical and chemical processes present in the atmosphere of this planet. The hot day-side of this planet is of particular interest, as it could habour vapourized rock that we could detect in the form of SiO.
Determining the amount of SiO in the atmosphere of this planet can teach us about its possible formation pathways. This will bring us closer to solving the question of how these fascinating planets form. For detecting SiO on WASP-121b and determining its amount, our team works on JWST/MIRI eclipse data of this planet, obtained in Cycle 2 with the program GO 2961 (PI: Paul Mollière).

The Lagoon Nebula (M8) is host to multiple regions with recent and ongoing massive star formation, due to which it appears as one of the brightest H II regions in the sky. M8-Main and M8 East, two prominent regions of massive star formation, have been studied in detail over the past few years, while large parts of the nebula and its surroundings have received little attention. These largely unexplored regions comprise a large sample of molecular clumps that are affected by the presence of massive O- and B-type stars. We established an inventory of species observed towards 37 known molecular clumps in M8 and investigated their physical structure. We compared our findings for these clumps with the galaxy-wide sample of massive dense clumps observed as part of the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). We find clear and widespread effects of stellar feedback on the molecular clumps in the Lagoon Nebula. While the radiation from the O- and B-type stars possibly causes fragmentation of the remnant gas and heats the molecular clumps externally, it also gives rise to extended photon-dominated regions on the clump surfaces. Despite this fragmentation, the dense cores within 38% of the observed clumps in M8 are forming a new generation of stars.
This study started as my master thesis, but is now published. Feel free to give it a read!

Studying the physical and chemical processes leading to the formation of low-mass stars is crucial for understanding the origin of our Sun and the Solar System. In particular, analyzing the emission and absorption lines from molecules to derive their spatial distribution in the envelopes of young stellar objects is a fundamental tool to obtain information on the kinematics and chemistry at the very early stages of star formation. We examined in detail the spatial structures and molecular abundances of material surrounding the very well-known low-mass binary protostar IRAS 16293-2422 and the prestellar core 16293E, which are embedded in the Lynds 1689 N dark cloud. Our new observations confirm the scenario of an outflow arising from IRAS 16293-2422 interacting with the prestellar core 16293E. This is inferred from the velocity and linewidth gradient shown by several deuterated species closer to the outflow-core interaction region in 16293E. We observe a large-scale velocity gradient across the molecular cloud which coincides with the rotation of the envelope around IRAS 16293-2422 reported previously in the literature. A comparison with JCMT SCUBA-2 450 μm dust continuum maps and our data suggests that emission peak W2 may be related to a colder dust source rather than a shocked region. The newly derived column densities and temperatures for different species, combined with the molecular spatial distribution in all sources, indicate clear chemical differences between the protostellar source, the prestellar core and the shocked positions as a result of the diverse physical conditions at different locations in this region.
The paper is available online, go check it out!

Studing sub-Neptune atmospheres is a big challenge as a consequence of the small planet size. TOI-700c is an exciting opportunity for us to study an object sub-Neptunian in mass, but larger in size as the average sub-Neptune. This extra-bit of signal will help us to unreval the composition of this relatively cold planet.
To obtain a first glimpse on this planets atmosphere, we use data obtained with WFC3 on the Hubble Space Telescope. We stay tuned for more data as further observations of this planet will follow.

During the Alpbach Summer School 2023, we created "Exodus" as a space mission to directly image the escaping atmospheres of nearby exoplanets. The goal is to observe Neptune-like planets with orbital periods longer than 100 days and to link possible atmospheric escape to the stellar activity. This could help us to understand the mechanisms involved in planetary mass loss. For an overview poster, click here.