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 fourth 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 four 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 protoplanetary discs, which is reflected by the breadth of my projects. More specifically, I am interested in:

  • Planetary atmospheric composition and its provenance
  • Atmosphere-interior interaction and its observable consequences
  • Planet formation and accretion of envelopes onto cores
  • Dust evolution in protoplanetary disks and consequences for planet formation
I use observational, analytical, and numerical methods in my attempts to study these areas. For more details, please take a look at the projects I am involved in.

Current and Past Projects



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

Selected 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, 489, 3896, arXiv:1908.11377, astrobites
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, 158, 244, arXiv:1910.07523
6. Zhang, M., Chachan, Y., Kempton, E. M.-R., Knutson, H. A., & Chang, W. 2020, PLATON II: New capabilities and a comprehensive retrieval on HD 189733b transit and eclipse data, ApJ, 899, 27, arXiv:2004.09513
7. Chachan, Y., Jontof-Hutter, D. J., Knutson, H., et al. 2020, A featureless infrared transmission spectrum for the super-puff planet Kepler-79d, AJ, 160, 201, arXiv:2008.05480

ADS Full C.V.

Current and Past Projects

Spectroscopic Observations of Atmospheres

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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Older Projects

Studies of Saturn's differential flow and gravitational moments, Venus' circumsolar ring (Github), phase transformations of oxides of Iron, and moleculer spintronics.

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