Maybe Everywhere, It Turns Out
As everybody knows, the Kepler Mission has been finding planets in the little section of the galaxy it has been studying for some years now. More than 4,000 planet candidates are out there, spied out by Kepler’s instruments. But, are those the only planets “out there”? Of course not. Astronomers think that exoplanets are ubiquitous—that is, they’re everywhere. One in five stars has Earth-similar planets orbiting in their habitable zones (the regions where liquid water could exist on their surfaces). Most stars in our galaxy have at least one planet.
That’s pretty reassuring if you’re into the search for other worlds. So, here’s some more good news: Spitzer Space Telescope and a ground-based observatory called the OGLE Warsaw Telescope at Las Campanas Observatory in Chile, spied a gas giant planet about 13,000 light-years away from us toward the central bar of the Milky Way Galaxy. OGLE was built to survey the sky looking for planets, and Spitzer is uniquely positioned to give us an infrared look at planets once they’re found.
Astronomers are interested to find out if planets are more common in the region where this one was found, part of the galaxy’s central bulge. The center of the galaxy is likely to give us a view of more stars, and more stars means more chances for an event called “microlensing” to take place. That happens when one star passes between us and other one; as it does, the nearer star’s gravity acts as a lens to magnify and brighten the more distant star’s light. It can also reveal the presence of a planet circling the foreground star.
Astronomers are using microlensing to find and characterize planets up to 27,000 light-years away in the central bulge of our galaxy, where star crossings are more common. This technique has yielded about 30 planet discoveries so far, and the most distant known planet it has found is about 25,000 light-years away from us.
Astronomers use OGLE to find the planets, and Spitzer to pinpoint their exact locations, which is a long and complex process. The results, however, are expanding the number of known planets and their locations, and giving even more evidence to astronomers that planets are pretty commonplace across the galaxy.