In this series of posts, we sit down with a few of the keynote speakers of the 233rd AAS meeting to learn more about them and their research. You can see a full schedule of their talks here!
Dissecting the chemistry of protoplanetary disks
Our knowledge of the history of planetary systems is riddled with gaps, much like the protoplanetary disks themselves — which are ironically also the best candidates to help us understand the birth and evolution of planets. While the theoretical modeling of disks has been there in the works since well before the discovery of the first exoplanet, well-resolved observations needed to constrain the physical and chemical processes in play have been possible only recently. In this context “ALMA has really changed the way we can image the chemistry of disks and the number of molecular species we can detect now”, believes Dr. Lauren Ilsedore Cleeves. Dr. Cleeves, a professor of Astronomy at University of Virginia and this year’s recipient of the Annie Jump Cannon award will be giving a plenary lecture at #AAS233 about her work on connecting the chemical diversity of protoplanetary disks with the outcomes of planet formation.
Recent advances in imaging the dust and gas emissions from protoplanetary disks using facilities like ALMA and SPHERE have enabled tracking the signatures (in the form of rings, gaps, and spiral features) of planet formation in these disks. In addition to understanding dust agglomeration into bigger planetesimals and ultimately the solid planet cores, mapping the molecular emissions of chemical species bearing Carbon, Nitrogen, and Oxygen using these observations can actually help in getting a handle on how different molecules in the disk are tossed around and reprocessed before they end up in the planets and asteroids. “There are many things our solar system is not,” says Dr. Cleeves, and building a complete picture of the possible planet formation pathways really needs these observations from the earliest stages of a protoplanetary disk.
Dr. Cleeves has been engaged in probing protoplanetary disks since her undergraduate studies at Rice University when she started working on a survey of the Cygnus OB2 association to get a complete photometric near-infrared census of young stars and disks in the region. She recalls working on this project as “a wonderful and definite research experience”, which gave her “a lot of liberty for her own efforts and work”. Describing herself as “a kid who got interested in astronomy in the 5th grade and never grew out of it,” she attributes her interest in astrochemistry to this early undergraduate research experience along with a combination of hard work, luck, and “being surrounded by a group of some fantastic mentors.”
The effect of stellar activity and other ionizing sources on the gas composition of the disk is another topic that has recently caught Dr. Cleeves’ interest. Energetic X-ray flares from the star can affect the ionization structure of the gas which can significantly dominate the disk chemistry. Dr. Cleeves and her group are currently working on obtaining sub-millimeter radio measurements of H13CO+ molecule in some of these disks over a long time baseline to track changes in the levels of ionization across the disk. This can also help in understanding how magnetic fields get coupled with the disk material.
What advice does she have for students starting their careers? “Expose yourself to as many potential research topics you possibly can as an undergrad,” she says. Try your best to focus on developing basic skills like programming early on, and try to obtain some experience of both observations and theory. To graduate students she advises attending more conferences “to get the pulse of the field”, and using conference talks “to create an artificial deadline for yourself” in terms of making your research presentable. Based on personal experiences she also emphasizes that “knowing when you have done enough for a project” is a hard skill and should be honed over time.
If you are interested in learning more about Dr. Cleeves work, be sure to check out her plenary lecture on “Tracing the Astrochemical Origins of Familiar and Exotic Planets” at 3:40 PM on Wednesday, January 9 at #AAS233.