It all began with Planet Hunters

Here is a great Planet Hunters story from Rebekah and Jennifer Kahn.

My sister and I are spending an entire week listening to and speaking with some of the top researchers of exoplanets. There, among the names of such renowned scientists as Batalha, Borucki, and Charbonneau from NASA and large universities, are Jennifer and Rebekah Kahn, undergraduates from small, all-women’s Smith College – registered participants! And as we take part in the international Kepler & K2 Science Conference, we think about how we got here and know that it all began with Planet Hunters.

Twin sisters born in China, we came to America when we were adopted at one year old, growing up on our eastern Connecticut farm, loving baseball, decorating the Revolutionary War graves just beyond our stone walls, and learning the constellations so brightly visible in our beautifully dark night sky. We were normal, healthy kids, except for our teeth. We each had two major dental operations in our very first years’ home and probably hold a world’s record in orthodontics, wearing braces from age 8 to age 17. All this required very frequent trips to specialized dentists in New Haven and Yale. Our dad, trying to make those visits educational if not enjoyable, each time took us to another Yale museum, library, or exhibit. The planetarium and observatory were our favorites (or second favorites, next to the collection of harpsichords that we were actually allowed to play). We became regulars there, looking through the telescopes, seeing each new show and exhibit, and gratefully receiving gift books from Heidi, the administrator.

It was a cold, clear January night in 2011 when the Yale astronomer assisting in observing asked us if we would be interested in becoming part of a new research project called Planet Hunters. A research project? Open to kids? We were ready the moment he asked. The chance to do “real” science and not just study it was exactly what we wanted – but of course, as we learned, first we had to do a bit more studying. You see, at age 14, like so many other people, we had never heard of exoplanets. While we had read science fiction stories, we did not know that 51 Pegasi B had made them a reality. So, Planet Hunters taught us about transits and light curves, and that led to transit depths, which then led to M dwarfs and the different star types, which in turn led to the Hertzsprung-Russell diagram, and then the effects of starspots and even eclipsing binaries. Taking part in Planet Hunters was not just our first chance to be “real” scientists (who were convinced that we would be the first to find another Earth), but also an immensely instructive project that made our education as painlessly distracting as our father had hoped our Yale visits would be. While we were too shy to participate in the on-line discussions, we read them avidly and learned much. Two years went by and, as home-schooled high schoolers still entranced by exoplanets, we were accepted into a distance learning “Computational Astrophysics” course from Dr. Laura Trouille (now a co-PI of Zooniverse) of Northwestern University, which published our term project Towards Eta sub Earth. Then as college freshman we spent the summer working on the Wesleyan Transiting Exoplanet Project for Prof. Seth Redfield, resulting in a paper on exoplanet light curves from white dwarfs, published by the Keck Astronomy Consortium.

And now, as undergraduate sophomores, here we are at NASA Ames Research Center. Jennifer is working with Dr. Jack Lissauer on discovering how varying the eccentricity of uniformly-spaced earth-sized planets in a Hamiltonian system affects the long-term stability of a planetary system, using the symplectic integrator REBOUND.  The aim is to examine the nature of planetary system formation over long periods of time.  Rebekah is working with Dr. Mark Marley looking at simulated data sets of exoplanet brightness to be obtained by the WFIRST Space Telescope with filter photometry; analyzing the brightness of each planet, and determining how much can be learned from photometry without spectra. The goal is to enable successful exoplanet characterization without a spectrometer flying on WFIRST, due to budget constraints.  We are both exercising our programming knowledge at the moment, modeling the processes and then varying the inputs to better understand the results.  We will be developing posters for later presentation and possibly short papers.  It is challenging and interesting work and we are doing a lot of late night reading to make sure we get it right.

Back at the conference we note that there are a significant number of talks discussing the pipeline and processing of Kepler data. Basic difficulties of SNR and PSF have led to applying advanced methods such as MCMC and ROBOVET. Yet all of these are simply designed to improve the extraction of light curves with less error; all are attempting to decide whether the data indicates an exoplanet or an artifact. That is exactly what we were, and are, all trying to do at Planet Hunters.
If imitation is the sincerest form of flattery, then the talk by Prof. Ian Crossfield on crowd-sourcing K2 data interpretation through his “Exoplanet Explorers” project is very high praise for Planet Hunters, which it so closely resembles. While we ourselves have not been active Hunters for a while, we are proud to be part of a project which has enabled citizens to make important discoveries with published papers, two Chambliss Award winners (we haven’t run into Daryll LaCourse who is supposed to be at this conference), and even gained some popular fame (or perhaps notoriety) through the possibility of aliens revealed in Tabby’s Star.

To be honest, we are not “natural” STEM scholars and sometimes think we should be pursuing our harpsichord studies rather than exoplanet research. We struggle with the concepts and work long hours to make clear our research goals, but the importance of the quest outweighs our challenges in pursuing it. While we didn’t discover Earth 2.0 when we were 14, we truly believe that we will be part of that discovery in our lifetime. And, for us, it all began with Planet Hunters.


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