Seeking Earth's Twin

October 19, 2012

Rheanna Sand


As humans, we may never know the answer to the ultimate, existential question, are we really alone? But we strive to in different ways - some use philosophy, while some pray to the invisible pink unicorn. Me? I read up on space research.

The search for life beyond our planet gets to the very root of our loneliness as sentient beings. SETI, of course, has been doing their part for decades, listening intently to incoming radio signals (and let's face it, we're all waiting for that Jodie Foster moment). The missions to Mars are also thinly disguised efforts to find extra-terrestrial life, even if it is only a microbe, or a strand of DNA which J. Craig Venter will "beam" back to Earth.

But the most exciting prospect, in my opinion, is the search for Earth's twin. If we can find a planet roughly the same mass, orbiting a star like ours, in the habitable zone where liquid water is stable, we might find creatures there. Hopefully, nice, friendly ones like Vulcans. But with our luck, we'd probably only find Conspiracy Bugs (*shudder*).

With the 750+ new planets discovered since 1995, you'd think the search would be a cakewalk. Well, you're obviously not an astrophysicist. Planets cause two changes in the signals coming from stars: their velocity (due to the gravitational pull of the planet) and their brightness (when the planet passes in front). Tiny planets like ours don't cause huge changes like a Jupiter or Saturn would. So, it's been difficult. And when they are discovered, they lie outside the habitable zone and so we don't care.

But a study from this week's Nature has gotten us tantalizingly closer. A group led by Stephane Udry reports "An Earth-mass planet orbiting alpha Centauri B," which just happens to be one of our closest star neighbors. The catch is, this planet is not in the habitable zone, and there is still only a 99.9% chance the planet is actually there (that 0.1% means a lot in science). However, if it is there, this suggests that a star system a mere 1.3 parsecs away may harbor an Earth twin in the habitable zone.

Kinda feels like we've been staring at models, waiting for them to notice us, when it was the shy one next door who finally made us feel... not so alone.


Photo credit: ESO/Wikimedia Commons



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