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Exoplanets Through Time: Atmospheric characterization of young transiting planets to trace signatures of formation and early evolution
Demographic studies of the mature exoplanets have revealed early evolutionary mechanisms such as atmospheric mass loss and thermal contraction play a key role in shaping the atmospheres of sub-Neptunes. However, this implies that the atmospheres we see for such planets at their current ages is not representative of what their initial atmospheres looked like. It is nescessary to know what their initial atmospheres were composed of to develop a deeper understanding of their formation and the effect of early evolutionary mechanisms.
During my PhD I started working on characterizing the atmospheres of extremely young (20-30 million year old) transiting planets using space based time series spectroscopic observations using the Hubble Space Telescope (HST) and James Webb Space Telescope (JWST).
The key questions I want to address are:
What is the nature and composition of the atmospheres of young transiting planets?
How do young transiting planets compare with each other?
How do young transiting planets compare with their mature counterparts?
What is the evolutionary timescale of their atmospheres?
The first glimpse at the atmosphere of a young transiting planet
We published the first atmospheric characterization of a young transiting planet known as V1298 Tau b (20-30 million years old) observed using HST (Barat et. al 2024 ). We found an extended and relatively clear primordial atmosphere with a large scale height. We could constrain a mass upper limit of this planet directly from it's spectrum. Mass measurements for young transiting planets have proven challenging for young planets owing to stellar activity using conventional methods (RVs), and it is likely that the method we demonstrate in this work could be a template for mass characterization of such planets. We find the atmosphere to be relatively metal-poor (1-2 orders of magnitude) compared to similar mass mature exoplanets. We also report a tentative low methane abundance which could hint toward an extremely high internal temperature.
How do the atmospheres of young transiting planets compare with each other?
To address this question, we compared the atmosphere of V1298 Tau b with it's sibling planet V1298 Tau c observed using HST (Barat et al 2024b) . This study presented the first comparative exoplanetology between multiple transiting planets in the same system. We found that V1298 Tau c could have similar mass and atmospheric composition compared to it's sibling. However, high altitude hazes cannot be ruled for this planet. We look forward to JWST observations of this planet to reveal it's true nature.
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