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[music]
Tom Barclay: For the longest time, space seemed

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like a big, nearly empty place, and we were really only familiar

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with our home, Earth. But as we learned more,

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we realized there was actually a lot out there, including planets

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orbiting the Sun, and even other stars.

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To get to these more distant worlds, though, it helps to start thinking of space

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as a bunch of nested bubbles. Our first bubble

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is the magnetosphere—Earth’s invisible magnetic field that

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protects us from high-energy particles and radiation from the Sun,

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allowing life as we know it to develop and thrive. The next bubble,

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just past the solar system, is the Heliosphere--

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the edge of the Sun’s influence, where the particles and fields

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of interstellar space take over. The two Voyager

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spacecraft have left this bubble and are our first interstellar

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spacecraft! It took Voyager 1 35 years, and it took

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Voyager 2 41 years to travel this far.

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The next stop is our nearest stars. The Alpha Centauri

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system, at just over 4 light-years away, is close by cosmic standards,

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but it would take either Voyager about 75,000 years to get

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there at current speeds. We clearly need to use other tools

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to look for worlds that far away. Enter Kepler,

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a space telescope that radically changed our understanding

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of planets outside our solar system—also known as exoplanets.

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In finding thousands of new planets, Kepler showed

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that there are more planets in our galaxy than there are stars!

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But Kepler looked at only a small fraction of the sky, and many 
 [on screen: the Kepler search region, which is approximately 3,000 light-years long]

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of the planets it discovered are too far away to study in much further detail.

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And that brings us to TESS, our newest planet hunter.

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The Transiting Exoplanet Survey Satellite works like Kepler,

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and over the next two years, it will scan almost the

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entire sky. By looking at closer and brighter stars, 
 [on screen: A comparison view of the Kepler and TESS search regions. Kepler's is a 3,000 light-year long cone, and TESS is a 30-300 light-year wide sphere.

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TESS will find—and measure the sizes of—dozens of small

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nearby planets best suited for detailed investigation

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by powerful telescopes on the ground and in space, like

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the future James Webb Space Telescope. And by doing

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that, we might finally begin to answer the question of whether

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Earth is alone, or whether there are worlds out there

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like our own—small and rocky, covered in oceans and

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dense clouds, or even—possibly—capable

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of supporting life.
[music]

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[music]

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[silence, then satellite beeping]

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[satellite beeping]