My time at IREx : Yayaati Chachan

IREx: What did you like most about your time in Montreal?
Yayaati: My wife and I just loved Montreal. We loved its different neighborhoods, vibrant culture, and diversity. We made some lifelong friends.

IREx: What was the most important project(s) you led at IREx?
Yayaati: Before coming to IREx, I had worked on a planetary system (Kepler-167) that has a Jupiter-like giant planet far away from the star and three super-Earths closer in. This project led to many interesting questions, one of which was about how efficiently dust is converted into planets at different orbital locations. At IREx, I developed this notion into a powerful framework that I then used to answer some open questions in exoplanetary science.

IREx: What question(s) were you trying to answer in this project?
Yayaati: I wanted to understand why super-Earths are more common and giant planets rarer around lower-mass stars. The other question that I became interested in was about figuring out whether very small planets (Ganymede- and Mars-like) exist around lower-mass stars. We are going to observe many of these stars using a microlensing survey and nobody knows how many such low-mass planets we will find.

IREx: What did you discover?
Yayaati: I found that the planet occurrence rate as a function of stellar mass could be naturally explained by the efficiency with which dust forms planetary cores. Lower-mass stars are simply more efficient at forming planetary cores. However, only a small fraction of such stars can form the more massive cores that are needed for giant planet formation. Using a single principle to explain a fairly wide range of observations was satisfying. I also found that Ganymede- and Mars-like planets should be very common around lower-mass stars. I am excited to see how well this prediction holds up against upcoming observations. Both of these projects were done in collaboration with professor Eve Lee.

IREx: What motivates you in exoplanet research?
Yayaati: Exoplanetary science is an incredibly observation-rich field. I am interested in all the different aspects of planets: their interiors, atmospheres, and orbital architectures. As a physicist, it’s exhilarating to use basic principles from different sub-fields to build theories that connect to these observations. 

IREx: Why do you think people should be interested in this kind of work?
Yayaati: Every star in the Milky Way (and other galaxies) likely has a planetary system around it. This is an extremely important discovery and it is shaping astronomy both scientifically and in the public conscience. What kind of planets do most stars have and what are their orbital configurations? How common is a configuration like our solar system’s? What is the outcome of planet formation around stars of different types and in different environments? We have so many interesting questions that touch the deep innate curiosity that humans have about the universe.

IREx: How will your time with us help you in your new job?
Yayaati: My time at IREx taught me how to be an independent researcher and work on the problems that are of interest to me. I had many opportunities to share my work with summer undergrad researchers, colleagues, and the general public. This provided me with some valuable lessons in how to effectively share scientific work with a wide range of audiences. I also had the opportunity to work with some undergraduate students at IREx: that was rewarding and instructive for me as a mentor. One of them (Emilia Vlahos) even led and published a paper on how planetesimals impact and alter the composition of planetary atmospheres. Conversations and collaborations with other postdocs (Space telescope JWST proposals with Romain Allart), graduate students (a paper on WASP-121 b with Stefan Pelletier), and faculty at IREx were quite enriching and helped me further broaden my knowledge base.