How Will We Know What Kepler’s Finding?

Now that the Kepler mission is on its way to final orbit and commissioning, astronomers are excited about the possibilities for new planets to be found “out there” in the nearest 3,000 light-years of space.  It’s worth remembering, however, that the Kepler spacecraft will be identifying planetary “possibilities” — that is, it will study star fields over time; in its data will be stars that appear to flicker.

The Kepler folk have a very cool interactive page that helps you understand how the spacecraft does its search (note, the link leads to a Flash-activated site), but essentially it looks for those flickers of star light and then relays that information to scientists for further study. There are thousands of stars to look at, so once Kepler commences on its official search mission, the datasets could be quite large. And who knows what we’ll find out there?

There are several possibilities about what causes stars to flicker, and only one of them is a planetary system.  A star could flicker because it’s variable – that is, it has some intrinsic (exclusive to itself) mechanism that causes its luminosity to brighten and dim on a regular schedule. All those stars will be of great interest to folks who study variables — including the American Association of Variable Star Observers.

Another possibility might be gravitational lensing events.  These occur when something  massive passes between us and a more distant object. Of course we’re familiar with gravitational lensing by distant galaxy clusters, but it can happen that something will do the same thing to a star in our own galaxy, causing its light output to appear to flicker. The late scientist Bohdan Paczy?ski was quite interested in such events, and the OGLE survey (among others) does real time studies of such events in our galaxy.

So, before Kepler scientists can confidently state that they’ve found a planet around another star, they have to take into account those other possibilities.

Once they think they’ve got a candidate, that’s when people like Geoff Marcy (of the University of California at Berkeley) step in and observe those stars using observatories such as the W.M. Keck telescopes in Hawai’i.

They essentially look for planets that are “transiting” the disks of the stars — that is, they pass in front of the star from our point of  view. That transit causes the flicker of starlight that betrays the existence of a planet.

The Keck team, headed by Marcy, will start looking for planetary candidates using Kepler data starting in late July of this year.  So, keep your eyes open for news from the exoplanet front. It’s bound to be interesting!