It's a Long, Long Way to Alderaan, but Kepler 10B is a Sight Closer

Size comparison between Earth and Kepler 10b.

Delta Vega, Alderaan, Malacandra, Altair IV, Kepler 10-b. Which one of these worlds is not like the other? Answer: Kepler 10-b. Why? Because among the thousands of small, rocky, Earth-sized planets that we have come to know over the past century, Kepler 10-b is not a piece of fiction, but real.

After over a century of science fiction storytelling involving distant aliens worlds—many of which are depicted as being not so unlike Earth, right down to oddly similar vegetation, human-like inhabitants, and one particular rock formation that is the spitting image of one I’ve seen in the Mojave desert—NASA’s Kepler mission has made good on its “promise” to find an Earth-sized exoplanet. “Sci-Fa” has finally caught up with Sci-Fi….

Kepler 10-b: 1.4 times Earth’s diameter, 4.6 times Earth’s mass, and 8.8 grams per cubic centimeter average density. In all the physical categories, a heavy-weight compared to Earth’s newly (dare I say) demoted middle-weight status. Were you to stand on Kepler 10b’s surface, you would weigh about 2.3 times what you weigh on Earth. (Interestingly, that’s just a small bit less than you’d weigh if you could stand on the surface of Jupiter—if Jupiter had a solid surface, that is; imagine instead that you’re standing on a floating gas mining facility, like that one in the second Star Wars movie….)

But how Earthlike is Kepler 10b? Well—not knowing anything about its atmosphere (if it has one), the fact that this rocky planet is about twenty times closer to its star than Mercury, and its surface is estimated to be 2,400 degrees Fahrenheit, means that it’s hot enough down there to melt most minerals, as well as about half of the list of metals you might jot down mentally. Since I keep alluding to worlds out of science fiction, I guess I’d say this makes Kepler 10b more like the planet from Star Trek (the original series) inhabited by the hot rock beings who recreated Abraham Lincoln, among other figures…okay, I’ll try to stop….

Though the first finding of an Earth-stature planet is a really big deal (it shows us evidence that other planets Earth’s size do exist beyond our solar system), this hit is actually only halfway to the bullseye of the Kepler agenda (Kepler the spacecraft, that is). Kepler’s ultimate goal is to find an Earth-sized planet orbiting its star within its “habitable zone”: at the right distance for its star’s light to allow liquid water to exist on the surface. (In other words, where most of the invented worlds of science fiction serendipitously revolve….)

How about a closer look? Well—it took the Kepler spacecraft and the enormous ground-based Keck Observatory telescopes just to detect Kepler 10b’s presence, by observing the tiny amount of light the planet blocks as it crosses in front of (or “transits”) its star (Kepler’s method), and by the gravitational tug it has on its star (Keck’s confirming observation). Why can’t all this telescope power give us a nice picture of what the planet actually looks like?

Well, consider that the Hubble Space Telescope, which has given us the best image of Pluto so far, has only revealed Pluto as a globe of blurry, slightly different-shaded regions—about as clear an image as a near-sighted person would have of the Moon without their contact lenses, and no telescope. And at a distance of 560 light years, Kepler 10b is over 900,000 times farther away than Pluto!

We’re still a long way from Delta Vega, or Altair IV, with their vivid vistas of distant outposts and extinct alien civilizations—but we’re now a great deal closer to a real other-Earth….

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