2018-10-19

target selection; rock and metal

At Flatiron we have purchased a share in the Terra Hunting Experiment, which will be a big, long-term radial-velocity monitoring program with HARPS3. Today Megan Bedell (Flatiron) and I had a conversation about target selection for that survey. There are many choices that could be made in target selection that could make populations or astrophysics inferences very difficult or even impossible later. These conversations remind me of the great and hard work that went in to target selection in the SDSS family of surveys.

The day ended with a great talk by Leslie Rogers (Chicago) about the things that set planet sizes (as a function of mass). She always phrases her results in terms of what isn't rocky, because of the one-sided-ness of some or most of the composition-related observational uncertainties, but it sure looks to my eyes like the smallest planets are rock and metal, like the Earth. She has one extremely good case, which is orbiting so close to its host star that tidal-disruption arguments come in to play! She also was optimistic that transit-timing information might be informative in the near future. There were jokes about water planets and soda-water planets, because many planets that are rich in water are also expected to be very rich in CO2.

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