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Course: MIT+K12 > Unit 1
Lesson 2: Earth and spaceHow to discover a new planet
Thousands of planets - ones that look totally different than what we're used to (and could host life!) - exist outside of our solar system. But we're only just now starting to find them! Ashley takes you behind the simple technique that astronomers have been using to discover these curious new planets.
Want to join the conversation?
- How many earth like planets have scientists discovered or are known?(8 votes)
- It is estimated that we have discovered around 40 billion Earth-sized planets, with 11 billion having a sun like ours.(3 votes)
- how many planets are there that are just like earth?(2 votes)
- we can live in different solar systems.(2 votes)
- how can we live in a different solar system(1 vote)
- for everyone asking about how many earth-like planets scientists have discovered, check out Tim Urban's "Fermi Paradox" article. It is really neat and worth reading about!!(1 vote)
- can we live in any different solar system(0 votes)
Video transcript
Twenty-five years ago, most people would have told you that there are only nine planets in the universe. Since then, we've lost one -- sorry Pluto -- but we've discovered thousands of others. So what happened? Did astronomers suddenly get a new pair of glasses? And now we're meeting all of our new neighbors? Well, no. It turns out, we could have seen these exoplanets all along - But we only recently figured out exactly where and how to look. We call these new planets, 'exoplanets' or 'extrasolar planets.' These are planets outside of our own solar system. Up until a few decades ago, we only knew about planets in our own solar system, like Venus, Mercury, and Earth. But in the last twenty years, we've
discovered over a thousand confirmed planets outside of our own solar system and over 3,000 candidates that are
probably planets. In fact, scientists think that there are
quintillions of planets in our universe that we just haven't seen yet. We've known for the last 400 years about our nine -- well eight -- planets in our solar system. So how are we now just finding all these
other planets? The simple answer is, we've built telescopes that are made to find them and they use something called 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 can't see my features, but you can see
my outline, and that's how you know I'm there. And that's exactly how the transiting method works. This is real space telescope data. What scientists do is that they monitor the brightness of a star overtime and what they look for are these tiny dips in the overall light and that tells you that there may be a
planet around that star. The transit method needs planets that orbit their star quickly so that we can get lots of transits and get a good signal. This means that the planets need to be close to their star. Now, in our own solar system, the planets that are closest to the star are the small, rocky planets like
Mercury, Venus, and Earth. Because astronomers used to think that
every planetary system had to look like our own solar system, they thought that the planets that were close enough to the star to detect with the transit method were too small to see with their old
telescopes. So they didn't even bother looking! Had they looked, scientists could have found a Jupiter-sized planet right next to its host star. It turns out, 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 been able to find large
planets next to their stars, but we've built better telescopes that can find these small, rocky planets, too. For example, 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's going to be launched in 2017 is being built right now by Google, MIT, and NASA. TESS's main job is to look for exoplanets around the brightest and closest stars to our own solar system. With any luck, she'll find planets that are close enough that we can follow them up with other space and ground-based telescopes to better understand their atmospheres and climates. It's amazing that such a simple method can help us find so many new planets. Just
by looking for dips in brightness, we might be able to find a planet that
can host life. All we needed to know was exactly how and where to look.