Exoplanets: Planets Outside Our Solar System

4 minutes

Twenty-five years ago, most people would have said that there are only nine planets in the universe. Since then, we've lost one-- sorry, Pluto-- but we've discovered thousands of others. Did astronomers get new glasses and now we're meeting all of our new neighbors? No. We could have seen these exoplanets all along. We only recently learned exactly where and how to look. We call these new planets exoplanets, or extrasolar planets. These are planets outside of our own solar system. A few decades ago, we only knew about planets in our own solar system. In the last 20 years, we've discovered over a thousand confirmed planets outside of our solar system and over 3,000 candidates that are probably planets. Scientists think that there are quintillions of planets in our universe that we haven't seen yet. We've known for 400 years about our nine-- well, eight-- planets in our solar system. How are we now just finding all of these other planets? We've built telescopes that are made to find them, and they use the transit method. Here's an easy way to think about it. This light is a star, and I am a transiting exoplanet. When I pass in front of the star, you see my outline and know I'm there. That's how the transiting method works. This is real space telescope data. Scientists monitor the brightness of a star over time. They look for tiny dips in the overall light. That tells you there may be a planet around that star. The transit method needs planets that orbit their star quickly so we'll get lots of transits and a good signal. The planets need to be close to their star. In our solar system, the planets closest to the star are small, rocky planets like Mercury, Venus, and Earth. Because astronomers believed that every planetary system had to look like our solar system, they thought planets that were near the star and detectable with the transit method were too small to see with their old telescopes. Had they looked, scientists could have found a Jupiter-size planet beside its host star. Exoplanet systems are nothing like our own solar system. In fact, they're changing the way we see and study planet formation in our universe. Not only have we found large planets next to their stars, but we've built better telescopes that can find these small, rocky planets too. NASA's Kepler telescope has found thousands of exoplanets using only the transit method. And now, the next generation is coming. This is TESS, the Transiting Exoplanet Survey Satellite. She'll be launched in 2017 and is being built by Google, M.I.T., and NASA. TESS's main job is to look for exoplanets around the brightest and closest stars to our solar system. With luck, she'll find planets that are close enough to be studied with other telescopes to better understand their atmospheres and climates. It's amazing that a simple method helps find new planets. These dips in brightness might help us find a planet that can host life. It took learning how and where to look. Accessibility provided by the U.S. Department of Education.


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Astronomers are beginning to locate thousands of planets that exist outside of the solar system. Scientists provide a behind-the-scenes look at the simple technique that astronomers are using to discover these curious new planets. Part of the "Science Out Loud" series.

Media Details

Runtime: 4 minutes

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