Scientists were excited about the possibility of the first rocky exoplanet—but it turns out, they weren’t quite right.
Exoplanet astronomy—the search for planets orbiting other stars—has two major goals. The first is to describe planets in our galaxy in all their weirdness and wonder. The second is to find planets as close as possible to Earth in size, composition, and position in their star system. Where we run into trouble is that the smaller the planet, the harder it is to find—and the more difficult it is to be confident we’ve detected a planet as opposed to something else.
That’s the case for a planet candidate known as Gliese 581g, described in 2010. It was an exciting discovery. Gliese 581g seemed to be the first rocky exoplanet to orbit its host star at the right distance for liquid water on its surface.
Now the verdict is in: Gliese 581g is an ex-planet, not an exoplanet. A new study, published in the journal Science, showed that what seemed to be the sign of a planet was more likely to be from the star’s “weather”—the same sort of magnetic fluctuations that cause prominences and sunspots on the Sun. Not only that, but a second planet in the same system, Gliese 581d, probably doesn’t exist either, for the same reasons.
The story of Gliese 581g highlights how hard exoplanet-hunting is, and how science at its best is self-correcting.
Your first response may be to say, “Stupid scientists! How could they get this so wrong?!” (You aren’t a very nice person, you know.) But that’s a mistake. The story of Gliese 581g highlights how hard exoplanet-hunting is, and how science at its best is self-correcting. All results have to be taken as tentative at first; if they survive under scrutiny or (ideally) replication by other researchers, we can trust them. It’s often messy or slow and can lead to ego clashes, but it’s how science works.
For the rest of the story: http://www.thedailybeast.com/articles/2014/07/06/the-exoplanet-that-wasn-t-there.html