March 31, 2022
Fellowship provides exceptional postdoctoral scientists with the opportunity to conduct theoretical, observational, and experimental research in planetary astronomy
The Heising-Simons Foundation today announced Michael Zhang, California Institute of Technology, Astronomy Ph.D.’22, as a recipient of the 51 Pegasi b Fellowship. He is among eight fellows selected for 2022. Zhang will be joining the University of Chicago Department of Astronomy and Astrophysics in the Fall term as a postdoctoral researcher as part of the fellowship, which was established in 2017 by the Heising-Simons Foundation, and named for the first exoplanet discovered orbiting a Sun-like star.
The 51 Pegasi b Fellowship provides up to $385,000 of support for independent research over three years; time and space to establish distinction and leadership in the field; mentorship by an established faculty member at the host institution; and an annual summit to develop professional networks, exchange information and ideas, and foster collaboration.
The Heising-Simons Foundation is dedicated to supporting the growing field of planetary astronomy studies of objects both within and beyond our solar system, bridging planetary science and astronomy. From improving our understanding of planetary system formation and evolution, to advancing new technologies for detecting other worlds, 51 Pegasi b Fellows make a unique contribution to the field.
Michael Zhang says, “From a young age, I was fascinated by the exotic conditions on other planets. Although they’re very different from Earth, I could imagine visiting them and possibly finding life on them.”
Now as an astrophysicist, he strives to uncover clues about their complex inner workings. His research probes what exotic atmospheres on other planets were made of, how they formed, and how they evolved.
One branch of his research considers mini Neptunes, planets two to three times the size of the Earth, “with a puffy atmosphere of hydrogen and helium that makes them look a lot bigger than they really are,” Zhang said. For these planets, stellar radiation evaporates their atmospheres when they are young. “I’ll be observing this mass loss process to understand more about which planets lose their atmospheres and which don’t,” he said.
Using the W.M. Keck Observatory telescopes and the Hubble Space Telescope, Zhang spotted two mini Neptunes in the process of transforming into super Earths—planets 1.6 to 1.75 times the size of Earth—as hydrogen and helium escaped from their puffy atmospheres. These significant discoveries help explain the size gap between the two most common classes of planets found outside the solar system and illuminate the nature and evolution of mini Neptunes.
The other branch of his research will use the giant James Webb Space Telescope (JWST) that just launched to study a planet even smaller than Earth, orbiting its star on a 0.3-day orbit. “Nobody’s ever studied the atmosphere of a sub-Earth outside the solar system before because it hasn’t been possible. Does the planet even have an atmosphere, and if so, what is it made out of? Hopefully in several months we’ll know,” Zhang said.
The launch of JWST will revolutionize the entire field of exoplanet atmospheres, especially the thermal detection of exoplanets, ushering in what Zhang sees as a new and exciting era. By far the largest space telescope ever launched, it has a collecting area 5.6 times that of Hubble and can observe at much longer infrared wavelengths over a much greater wavelength range.
JWST will allow the spectroscopic study of exoplanet atmospheres in unprecedented detail, so that, for the first time, astrophysicists can look at exoplanet molecular absorption features in the infrared spectrum for a large number of small rocky planets.
“By my rough count, there are 42 JWST General Observer programs in cycle 1 that focus on exoplanet atmospheres, in addition to many more in the Guaranteed Time Observer program and the Early Release Science program. These programs study a wide variety of planets, from potentially habitable rocky worlds to puffy planets with the density of cotton candy. Whatever JWST finds, I'm certain that it will surprise us. Exoplanets always have,” he said.
Joining the University of Chicago Department of Astronomy and Astrophysics for his postdoctoral research will expand the areas of the sky that Zhang observes by granting him access to a new telescope.
“I've been using the Keck telescope to look for escaping atmospheres around young mini Neptunes. Keck is amazing, but there's thirty percent of the sky it can't see because it's in the northern hemisphere,” he said. “UChicago's Magellan Telescope is in the south, which means I can go after a whole new set of planets.
This is an untapped gold mine. Until recently there were no instruments that can measure escaping helium in the south; Magellan's WINERED spectrograph will be one of the first,” he said.
Zhang looks forward to working with UChicago’s many faculty with overlapping research interests: “Edwin Kite, Leslie Rogers, and Jacob Bean, just to name a few. Jacob Bean, who will be my advisor, is actively working on both mass loss and JWST characterization of small planet atmospheres, which are precisely the two areas I plan to work on during my postdoc.”
The other fellows selected nationwide for the 2022 class are:
- Paul Dalba, University of California, Santa Cruz
- Leonardo Krapp, University of Arizona
- Brittany Miles, University of Arizona
- Malena Rice, Massachusetts Institute of Technology
- Eva Scheller, Massachusetts Institute of Technology
- Shreyas Vissapragada, Harvard University
- J.J. Zanazzi, University of California, Berkeley
The Heising-Simons Foundation is a family foundation based in Los Altos and San Francisco, California. The Foundation works with its many partners to advance sustainable solutions in climate and clean energy, enable groundbreaking research in science, enhance the education of our youngest learners, and support human rights for all people. Learn more at www.hsfoundation.org.