Category Archives: Keck Observatory

About Those Exoplanets

How Will We Know What Kepler’s Finding?

The galaxy neighborhood that Kepler will search for exoplanets. Courtesy Kepler Mission, painting by Jon Lomberg. (Click to embiggen.)
The galaxy neighborhood that Kepler will search for exoplanets. Courtesy Kepler Mission, painting by Jon Lomberg. (Click to embiggen.)

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.

The Keck telescopes on Mauna Kea are used for planet-hunting. The Kepler mission findings will keep it busy searching out exoplanets. (Photo by Laurie Hatch, used by permission; click to embiggen.)
The Keck telescopes on Mauna Kea are used for planet-hunting. The Kepler mission findings will keep it busy searching out exoplanets. (Photo by Laurie Hatch, used by permission; click to embiggen.)

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!

New Clouds at Titan

Titan as seen by Gemini and Keck
Titan as seen by Gemini and Keck

This is kind of cool. Astronomers using the Gemini and Keck observatories on Mauna Kea, Hawai’i have spotted clouds in the atmosphere of Saturn’s largest moon, Titan. This isn’t the first time clouds have been found; astronomers have also seen them at Titan’s south pole and reasoned that they were caused by solar heating of the polar region.

However, these new clouds were spotted in early 2004 at the mid-latitudes of the moon, and are not likely to be caused by solar heating. So, what could be driving the formation of cloudy features in Titan’s nitrogen atmosphere? One explanation could be something happening on the surface that affects the atmosphere, like methane geysers or volcanoes that spout icy slush instead of lava (called cryovolcanism). It’s also possible that these features are being driven by some sort of changes in the global winds that circulate in the upper parts of Titan’s atmospheric blanket. The good news is that astronomers have a reporter “on site” in the form of the Cassini-Huygens mission. It’s likely the spacecraft has also recorded observations of these clouds and we may hear more about them from Cassini mission scientists. Incidentally, those researchers are gearing up for a big event on Christmas Day, 2004: the launch of the Huygens probe toward Titan, and an eventual surface landing sometime in the middle of January. Keep an eye out for more Titan news in the coming days and weeks!