Tuesday, January 05, 2010

AAS meeting Day 1: planets and people everywhere

Today begins day 2 of the 215th meeting of the American Astronomical Society in Washington, DC.  As I said yesterday, follow me on Twitter, or search Twitter for #aas and #aas215 hashtags for up-to-the-minute tweets with news and science results.

There are 3300 astronomers registered for this meeting, easily making it the largest meeting of astronomers in the United States ever.  The halls and restaurants are crowded.  I feel sorry for the hotel staff, as they try to keep us all in line.  Herding astronomers is worse than herding cats -- if you clap your hands and shout at a cat, there's a chance it will acknowledge your presence, or at least flinch.  Astronomers just ignore all other noise and keep arguing about the efficacy of  Bayesian analysis.

Yesterday, the biggest science results were from NASA's Kepler Mission, which is searching for planets around other stars.  You can read their press release here.  Kepler has been looking for planets for months.  Yesterday's announcement was of five new planets, all Neptune- to Jupiter-sized and all very close to their host stars.  You might expect more, because it was launched in March and these hot planets only take a few days to complete an orbit, but the Kepler team has to do several levels of follow-up research to make sure that they are seeing a planet and not some other type of variable star.  That's hard and slow, and even slower because the area of sky Kepler is looking at (in the constellations of Cygnus and Lyra) are not visible from the ground during the winter and early spring, so right now there is little work that can be done.  The current official tally is 5 confirmed planets, 52 suspected planets, 65 stars with uncertain signals, and 65 stars with planet-like signals that are really something else.

One of the planets is very low density, about as dense as Styrofoam.  We have no clue how you make such a fluffy planet.  According to theory, if you take hydrogen and helium, the lightest and most common elements in the Universe, and you make a Jupiter-mass ball of this gas, it should be many times more dense than this planet.  I think this is telling us that we don't understand the physics of dense hydrogen and helium very well.  This is good, because it means planets can tell us something about physics as well as about astronomy! 

I was joking with friends about how, in a 6th grade science fair project, I made models of comets out of Styrofoam.  Little did I know that I was 25 years ahead of my time in understanding the building blocks of planets!

Another hard-to-explain object that Kepler found is a star with a very hot star orbiting it.  The odd thing is that the very hot star is a couple times the radius of Jupiter.   My first thought was this might be a white dwarf, but white dwarfs are only the radius of Earth and much smaller in diameter than Jupiter.  My next (and current) thought is that this hot star must be what we call a "hot subdwarf".  These are stars that, due to an interaction with a close companion, are essentially the bared stellar nuclear reactor normally buried deep in the core of a normal star.  The Kepler team claims to have ruled this out, but I found their explanation of that unsatisfactory.  Really, though, there's no way to tell until we can get more ground-based information this summer.

There's much more to say, but I need to get to a talk about water on Mars.  Follow my tweets!

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