The discovery of a possibly Earth-like planet in the Milky Way, Kepler-452b, has been big news. The exoplanet (planet outside the solar system) has a great chance of being very similar to Earth. The most compelling thing about it is the possibility for alien life on it. There's plenty of other things that can get a mention, though.
First off: all "pictures" of Kepler-452b are artist conceptions. The planet itself is too far away to be photographed. Of course, this leads many to wonder how astronomers know it's an Earth-like planet in the first place. Well, they don't, not for certain. The chances of it being Earth-like are based on its habitable zone (a series of calculations that determine whether the planet would be too far or too close to its sun for life, based on the possibility of liquid water on the planet) and Kepler-452b is within the right range. Its size indicates it's probably a terrestrial planet like Earth rather than a gas planet with no solid surface like Jupiter. While it's bigger than Earth, it's also rotating an older sun and is farther away from it than Earth is. The sun is very like Earth's sun. Theoretically, this means that plants, animals, and even people could live there, once accustomed to the increased gravity.
Kepler-452b is not alone in the "potentially Earth-like" category: while no planet has been found that is almost exactly like Earth, there are 31 potential candidates so far. Ten are Earth-like in size while 21 of them are "Super-Earths" with potentially more gravity and surface area. Overall, 1030 exoplanets have been confirmed to exist and analysis of pictures taken with the Kepler space telescope has given over 4 thousand potential planets.
The search for these exoplanets is partially based in the search for extraterrestrial life. The SETI project has been monitoring the planet for radio signals, but none have shown up. This doesn't mean there's no chance of life on the planet, even of the intelligent type, but it's not likely to contain an advanced civilization. The search is also based in the desire to discover how many Earth-like planets exist in the galaxy. Earth-type planets were once thought to be rare, but the confirmed number of exoplanets that may be Earth-like is a much bigger percentage than anyone thought before.
While ET might not be hanging out on Kepler-452b, bacteria, plants, animals, and even intelligent aliens might be there. And whether it's bacteria or something far more advanced, that would be the biggest news in astronomy indeed.
(Photo via NASA/Ames/JPL-Caltech/T. Pyle.)