Planets R Us

Tonight I went to an excellent lecture at the Museum of Science by Dr. David Charbonneau on recent discoveries of extra-solar planets. It was part of the Lowell Lectures on Astronomy series and is archived. Dr. Charbonneau and his colleagues were the first to discover an eclipse of an extra-solar planet across its sun and were also the first to detect the atmosphere of the same planet. It really was getting the information from the foremost authority and better yet, he was a fantastic presenter. Listening to this lecture, I wanted to take all the money Tom DeLay wastes and give it to this guy to do something important with.

Here were the big points. By taking very detailed measurements of the light coming from the stars they could detect the gravitational effects of the planets on the star. The planets they found were gas giants like Jupiter because they have enough mass to affect their star. Oddly they found some very close to their stars with orbits of only a few days, these are called hot giants. We've found about 150 extra solar planets so far. Based on the techniques used it's more likely to find such hot giants. With merely more time to look we should find large planets with larger orbits (detection involves noticing the whole orbit, if that takes 12 years, like Jupiter's orbit, we have to wait at least that long, we've only been doing this since 1995), though to detect planets with less mass may require different techniques.

After this gravitation method they tried measuring the brightness of stars over time and detect a difference when a planet passes in front of (eclipses) the star. These effects were very slight (a 1% difference) but still were done with small 4 inch telescopes, 4 mega-pixel cameras and a bunch of software. Once some of these were discovered they redid the experiment with the Hubble Space Telescope and got much more detailed results that confirmed the findings. In fact they were detailed enough that they would have revealed moons of these planets! NASA's Kepler Mission will use this technique much as Ventner searched for genes with his shotgun method, it will look at a large swatch of sky at look at 10,000 stars at once and measure brightness changes, looking for earth-sized planets.

The discovery a few weeks ago was that they looked at one of these known hot giants in infrared as it passed from behind it's star. These planets give off more infrared light then visible so it's easier to see (particularly when you know exactly where to look) and they got some light directly from the planet which can tell us it temperature and a little about the atmosphere.

I also found out about the Community Solar System which is a scale model of the solar system around the Boston area. The Sun is at the Museum of Science and is about 12 feet in diameter, this is a scale of 1 to 400,000,000. Mercury, Venus, Earth and Mars are short walks from the museum. Jupiter is in South Station and Pluto is out in Newton at Riverside station. In geekiest fashion, at this scale, a normal walk is the speed of light.