Cool Stars in the Summertime

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Cool Stars

June 24, 2012 to June 29, 2012

Barcelona, Spain


Stephanie Douglas

SPS Chapter:

During his talk at Cool Stars, Todd Henry of Georgia State University had the entire audience stand up and participate in an exoplanet dance. It was, quite possibly, the funniest moment of the conference.

Astronomers were told to perform different motions depending on what exoplanet search method each was most involved in. Those participating in the Kepler mission and other transit searches, which wait for planets to pass in front of stars and block the starlight, stood with their hands clasped behind their backs. Those using radial velocity searches, which look for the gravitational wobble of a star induced by a planetary companion, moved their heads back forth in “what we in America call 'the funky chicken,'” said Henry. The remaining members of the audience were instructed to move side to side and shake their heads back and forth while twisting their arms around in a circle to represent all the effects that could show up in a third, lesser-known method for finding planets around nearby stars: astrometry, or the precise measurement of stellar positions.

Cool Stars 17 provided a new meeting experience for me, and not just because of the dancing. I had been to the large winter meetings of the American Astronomical Society (AAS), but Cool Stars was smaller, more focused, and much more international. The conference is held every two years, alternating between the United States and Europe. This year 433 attendees gathered in Barcelona to discuss pretty much any starlike object that astronomers consider "cool" . . . everything from recently discovered room-temperature Y dwarfs, to old giant stars that measure a toasty 6,000 Kelvins.

The coolest hydrogen-burning stars, M dwarfs, are gaining a lot of attention. Bárbara Rojas-Ayala of the American Museum of Natural History explained to me that the details of M dwarfs were largely ignored for a long time. The stars were thought of as small, boring, and unimportant. But they are ideal hosts for detectable planets, and as Caltech's Kaspar von Braun stated during his talk, “You understand the exoplanet only as well as you understand the parent star.” In light of this, the entire last day of the conference was dedicated to M dwarfs as exoplanet hosts. M dwarfs make good hosts for detectable exoplanets because they are relatively dim compared to Sun-like stars. A planet transiting the face of a dimmer star will block a higher percentage of the starlight, making it easier to detect. Victoria Meadows of the University of Washington spoke about the habitability of exoplanets and explained that there are a huge number of factors that affect a planet’s ability to harbor life. Her talk focused on biosignatures that might signify life, as well as the effects of the host star’s spectrum and magnetic activity on habitability. She cautioned that we can only be sure that a planet is inhabited if we detect modulated electromagnetic signals coming from it; otherwise, we can only determine the probability that the planet hosts life.

Another area of interest at Cool Stars was the transition from M dwarfs down through the different classes of less massive brown dwarfs. Brown dwarfs have the same composition as stars but don't have enough mass to ignite hydrogen fusion. Due to their cool temperatures, brown dwarfs have cloudy atmospheres. Atmospheric models usually assume a uniform atmosphere, but that's probably not the case for many brown dwarfs. Several astronomers presented evidence that brown dwarfs vary over time as the objects rotate, indicating that, like Jupiter, brown dwarfs may have nonuniform bands or patches of clouds.

Very few undergraduates attended Cool Stars. I met only one other! Christine Wilson, from Saint Mary’s University in Halifax, Nova Scotia, presented her research on the supergiant star Epsilon Aurigae. We met because we were both staying in the same hostel, and we stuck together at many events throughout the week. The lack of other undergraduates made the meeting slightly more intimidating than the AAS winter meeting, where undergraduates make up a significant fraction of attendees. There were a good number of graduate students, however, and each of the three splinter sessions I attended included a graduate student talk.

Outside of the conference, there was plenty to see in Barcelona. The city is host to a myriad of buildings designed by the architect Antoni Gaudí. Christine and I, along with City University of New York graduate student Kay Hiranaka, spent an afternoon exploring two of Gaudí’s works: La Sagrada Familia and Park Güell.

Between the city, the astronomy, and the dancing, I had a great time at Cool Stars. //

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