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SciShow Space starts the year off with a bang, and the discovery of 8 Earth-like planets, two of which may be the most promising candidates yet for harboring life.
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(Intro)

With billions of stars in just our galaxy and billions of galaxies in the universe , it's hard to imagine that the earth is the only planet out there that can support life. but it's been tough to find other ones that can because life needs a tricky mix of conditions and finding potentially earth like planets hundreds of light years away is just plain hard.

Until this week , astronomers had only found 8 exoplanets that resemble our home world. the most promising of them being Kepler 186-F which was just discovered last April.
 
And when I say resemble I don't mean that they have trees and rainbows or a Nintendo, I just mean that if you squint really really hard and tilt your head a little they might look like planets that could possibly have something alive on them.

To be considered earth like, a planet needs to be small enough to be rocky but big enough to hold on to an atmosphere to keep the planet warm and protective from radiation.

But life also needs water at least as far as we know, so that means that a planet has to orbit with in its stars habitable zone where it is just far enough away from it's star to have temperatures between 0-100 degrees so that water won't freeze or boil away.

There's a reason this habitable zone is sometimes called the Goldilocks zone, All of these conditions have to be just right.  

So it's pretty exciting when on January 6th astronomers at the Harvard-Smithsonian Center for Astrophysics announced that they found 8 more earth like exoplanets including two of the most promising candidates yet for harbouring life.

Finding them of course was anything but easy. Exoplanets are too far away to see directly, but when they pass in front of their parent star they block a little bit of its light. So measuring the fluctuations in light is our best was of finding them. 

And since 2009 NASA has been using  the Kepler space telescope to do just that. Kepler is in what's called an earth trailing orbit meaning that it basically follows earth around the sun like Mary's little lamb. Monitoring the brightness of over 100,000 stars sending huge amounts of data back to earth every day for analysis.

The Harvard researchers used a NASA supercomputer named Pleiades to plot some of Kepler's latest data into light curves which map how much light a given star emits over time.

They analyzed these fluctuations in starlight and were able to identify possible planet candidates, estimating how big they were, how often they passed in front of their stars and how big their orbits were.

Eventually the team found 8 exoplanets that fit their definition of earth like 2 of which are taking the place of Kepler 186-F as most likely to be habitable; they're called Kepler 438-B and Kepler 442-B.

Kepler 438-B has a diameter that's just 12% larger than earth's. And astronomers figure it has a 70% chance of being rocky. Zipping around its red dwarf star every 35 days it gets 40% more light from its star than we do. So they estimate that it has a 70% chance of being in the habitable zone.

Kepler 442-B on the other hand has a diameter one third larger than earth's and has a 60% likelihood of being rocky. But it's further out from its parent star which is also a red dwarf. With an 112 day orbit it gets about two thirds as much light as earth does and turns out to have a whopping 97% chance of being in its stars habitable zone. Those are pretty good odds.

Unfortunately Kepler 438-B is 470 light-years away and Kepler 442-B is 1100 light-years away. Too far, using our current technology to get a closer look at either of them.

So even if Elon Musk invents a warp drive tomorrow it'll still be a really long time, if ever, before we'd know for sure if these newly found worlds are able to support life as we know it.

And of course just because a planet could support life doesn't mean that it does. But as we get better at finding exoplanets that are likely to be habitable we grow closer to finding out what might be out there.

Pretty good start to 2015.

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