July 24 – Twin Paradox

Today’s Factismal: The Kepler Satellite has discovered a near-twin of planet Earth, a mere 1,400 light years away!

There is good news out of NASA.  Kepler has found a planet that is a near-twin of Earth. It is called Kepler 452b; Kepler for the satellite that found it, 452 because it was the 452nd star checked, and b because it was the second planet found around that star. Given that Kepler has discovered more than 1,000 planets around other stars (and has evidence for another 3,000), perhaps we shouldn’t be surprised that we’ve finally found one that is only half again as large as Earth and circling a start much like our Sun. What might amaze us is how high the odds for an Earth-like planet are. At one in a thousand, that means that there could be 40 billion Earth-like planets in the Milky Way alone!

Of course, it might take a while to visit these planets. At 1,400 light years away, it would make the ultimate road trip. If we were to zip by as quickly as the New Horizons probe (fastest in the Solar System!), it would only take us 28 million years or so to get to Kepler 452b. (Are we there yet?) And once we got there, we might find things a bit disappointing. The planet orbits its star just a little further our than Earth orbits our Sun, so its year is longer at 385 days. (And only 225 shopping days until Grunchmark!) The planet is half again as big as the Earth; if it has the same density as the Earth, then the gravity would be 63% higher than ours. So a 150 person would feel as if there were another 94 lb person on her back. And the star it orbits is about a billion years older and 20% larger than ours, which means that it puts out nearly 10% more energy. So if Kepler 452b has an Earth-like atmosphere, then it could be much warmer than Earth thanks to greenhouse feedbacks. But if the atmosphere of Kepler 452b is much different than ours (e.g., no water or no CO2), then the planet could be much colder; we simply don’t know for sure at this point. And that means that visiting Kepler 452b could be like wearing a teenager on your back during a hot sticky summer (hello, Wallyworld!) or it could be like carrying a backpack of provisions while hustling through an arctic wilderness (hello, ton-ton!). We need to do mor eresearch before we can know for sure.

The locations of Kepler's discoveries as seen against the night sky

The locations of Kepler’s discoveries as seen against the night sky

Kepler's discoveries (exploded view)

Kepler’s discoveries (exploded view)

One thing we do know for sure is how Kepler works. Kepler stares at stars and looks for the dimming caused by the transit of a planet across its face. To put the problem into scope, it is like trying to tell when a bird is flying across the sky by looking for its shadow from space. It can be done, but it takes a lot of work, a really good telescope, and pinpoint concentration on a specific area.

So what has Kepler discovered during its time in space? For one thing, Kepler has discovered that planets are a lot more common than anyone other than a planetologist thought. We’ve seen planets around old, cold stars and planets around young, hot stars. We’ve seen planets close in and far away from their host star. We’ve seen stars with a single planet and stars with multiple planets. In short, we’ve gotten our money’s worth.

If you’d like to see what we’ve discovered, then why not head over to the Kepler Data explorer?
http://planetquest.jpl.nasa.gov/kepler/plots

And if you’d like to use Kepler (and other) data as you search for a planet to call your very own, then head over to:
https://www.zooniverse.org/project/planethunters

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