How much have we really learned about alien planets?
Twenty years ago, we knew nothing about any other worlds outside of our solar system. Now, we've discovered the Milky Way is teeming with planets just like Earth.
That's thanks to NASA's Kepler space telescope, which launched in 2009 to explore our galaxy's interplanetary systems. A new video from the YouTube channel Deep Astronomy highlights some of the telescope's amazing discoveries. Just check it out above.
"The Kepler space telescope has opened up a new era of astronomy in our lifetimes," Tony Darnell, video blogger and social media manager at the Space Telescope Science Institute, says in the video. "For the first time in our history when we look up at the night sky, thanks to Kepler, we know that there are more planets up there than there are stars."
So far, Kepler has looked at just a small slice of the Milky Way, discovering 3,538 potential worlds — 104 of them are in the so-called "habitable zone," meaning their environment could potentially support life, and 10 are about the size of Earth, according to NASA.
In fact, NASA data suggests that there are at least 8.8 billion stars with Earth-size planets in the habitable temperature zone. Wow.