Worlds Around Other Stars

From the moment I picked up my first astronomy book and discovered that the stars were like our sun, only very far away, it seemed obvious to me that planets around other stars must be commonplace, many of them surely harboring life. There were so many stars in the sky, it was hardly likely that our situation was unique. Yet in those days, not a single example of an extrasolar planet had been found, so it was still a matter of speculation.

In an episode of the Cosmos TV series, Carl Sagan informs a group of school children that within their lifetimes we should be able to figure out whether planets exist around nearby stars.

“That will happen in your lifetime,” he predicted. “And it will be the first time in the history of the world that anybody found out, really, if there are planets around the other stars.”

Over six thousand such exoplanets have since been discovered, of the several tens of billions that are believed to exist in the Milky Way galaxy. There are numerous techniques for detecting exoplanets, but the one illustrated above involves measuring how the brightness of a star drops as the planet moves in front of it – an event known as a “transit.” If an exoplanet’s orbital plane is somewhat aligned with our line of sight to the star, then we should see the star’s light grow slightly dimmer at the beginning of the transit, brightening up again when the transit is complete.  Exoplanet Watch is a citizen science project open to anyone who would like to participate. By taking part in the program, you can help fine tune the available data on exoplanet transit times allowing scientists to make more efficient use of space-based telescopes such as Kepler and TESS.