About me

To describe my love for astronomy,
I will resort to a few words by Vera Rubin:
"I became an astronomer because I could not imagine living on Earth and not trying to understand how the Universe works."

I am a second year graduate student in planetary science at Caltech. I have had the privilege of pursuing my long held childhood interest in astronomy and planetary science for the last two years. I grew up in Delhi and finished high school in Singapore on a SIA Youth Scholarship. I then moved to the U.K. to do my undergraduate study at the University of Cambridge, where I finished my bachelors in physics and masters in astronomy.

Research Interests

I have a broad interest in planets and discs, which is reflected by the breadth of my projects. Some of the questions I am interested in include:

  • How do planets form in protoplanetary discs?
  • What are planetary atmospheres made of and how do they interact with planetary interiors?
  • Can planet formation in binary star systems give us important clues?
  • What methods can be employed to determine the key observables of exoplanets?
  • Finally, how should we synthesise our knowledge of the solar system and of exoplanetary systems to develop a unifying framework?
It is my goal to use observational, analytical, and numerical methods in my attempts to answer these questions. For more details, please take a look at the projects I am involved in.

Current and Past Projects

C.V.

Education

PhD, California Institute of Technology, 2017-
Advisors: Heather Knutson and Dave Stevenson
M. Sci, Institute of Astronomy, University of Cambridge, 2016-17
Advisors: Cathie Clarke, Amaury Triaud, Richard Booth
B. A., Natural Sciences (Physics), University of Cambridge, 2013-16

Recipient of: Institute of Astronomy Prize, Dirac Prize,
Cambridge Commonwealth Trust Scholarship,
SIA Youth Scholarship

Publications

1. Chachan, Y. & Stevenson, D. J. 2018, On the Role of Dissolved Gases in the Atmosphere Retention of Low-Mass Low-Density Planets, ApJ, 854, 21, arXiv:1802.04296
2. Zhang, M., Chachan, Y., Kempton, E. M.-R., & Knutson, H. A. 2019, Forward modelling and retrievals with PLATON, a fast open source tool, PASP, 131, 034501, arXiv:1811.11761
3. Chachan, Y. & Stevenson, D. J. 2019, A linear approximation for the effect of cylindrical differential rotation on gravitational moments: Application to the non-unique interpretation of Saturn's gravity, Icarus, 323, 87, arXiv:1902.10728
4. Chachan, Y., Booth, R. A., Triaud, A. H. M. J., & Clarke, C. 2018, Dust accretion in binary systems: Implications for planets and transition discs (MNRAS, in revision)
5. Chachan, Y., Knutson, H., Gao, P., Kataria, T., et al., 2019, A Hubble PanCET Study of HAT-P-11b: A Cloudy Neptune with a Low Atmospheric Metallicity (AJ, submitted)

Full C.V.

Current and Past Projects

Planet Formation and Evolution

I use semi-analytical and numerical tools to study the formation and atmosphere-interior coupling in super-Earths as well as planet formation in binary star systems. (Chachan & Stevenson 2018, arXiv:1802.04296) (Chachan et al. 2018, MNRAS, submitted)

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Transmission Spectroscopy

Using Hubble Space Telescope and Spitzer data to characterise planetary atmospheres and develop forward models and retrievals to study their properties. (PLanetary Atmospheric Transmission for Observer Noobs: PLATON available on Github)

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