It seems increasingly likely that, as they stare at the heavens, astronomers are going to find an earth out there, or at least something that they can plausibly claim is a rocky planet where water could splash at the surface and — who knows? — harbour some kind of life.
But it’s also clear that, when they make their big discovery, the astronomers might want to hire movie director James Cameron to help with the special effects.
The roughly 400 planets that astronomers have found outside our solar system have not been earthlike by any stretch of the imagination. Most are hot Jupiters, which is to say they’re gas giants in scorching orbits. They’ve also been pretty much invisible, their presence inferred from fluctuations in starlight. The planet emerges from the data.
Astronomers will announce a new planet find with a graph, typically with a nice curving line that represents the periodic changes in starlight associated with the orbiting body. There are no pictures. Which is fine for scientists.
“To me, a spectrum is more beautiful than a picture,” said David Latham, a Harvard astronomer who came to Washington last week for the annual meeting of the American Astronomical Society. “A spectrum can tell you about the physics.”
Yeah, but what about seeing some clouds, continents, jungles? How about some flying reptilians or thundering ungulates? Why can’t astronomers produce a planet that looks more like the “exomoon” Pandora from Avatar?
“Sorry, they have a bigger budget than we do,” Latham quipped. Finding an earth-like planet is really hard.
Even detecting one of those hot Jupiters requires prolonged observations that pick up extremely subtle shifts in starlight. Keep in mind that it’s been only a decade and a half that we’ve been able to detect any of these planets outside our solar system. But the hunt has been fruitful. Astronomers say it’s increasingly obvious that the galaxy is lousy with planets.
Planets seem to be a natural byproduct of star formation. But from our vantage point, the feeble, reflected light of a planet is utterly lost in the glare of the star right next to it. Astronomers are developing techniques for blocking that starlight so that only “planetlight” remains. Such occultation requires exquisite engineering. It’s just a bit like trying to write the Book of Genesis on a grain of rice.
There was much discussion at the Washington astronomy meeting about a planet named COROT-7-b, discovered by European astronomers. In a NASA press release, it was referred to as the most earthlike planet found so far. But in fact, it’s only Earthlike in its size and density.
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