NASA’s Kepler Project announced on Dec. 5 that its astronomers have confirmed the first planet we know to orbit its Sun-like star in the “habitable zone.” Also known as the “Goldilocks zone,” the term refers to that distance from a planet’s star at which liquid water can exist on that planet’s surface. There are some 48 candidates for planets in the habitable zone. The “some” is justifiable given the rapid rate of discovery of extrasolar planets, of which over 800 have been found since 1995.
The planet, designated Kepler 22b , has twice Earth’s gravity, and a bit more than twice its radius. It is also an intimidating 600 light years from Earth. A great deal of enthusiasm has been gushed upon these habitable zone extrasolar planets. They are commonly referred to as, simply, “habitable.” Some overenthused commentators have even gone so far as to call them “Alien Earths” (see above). In fact we do not know if Kepler 22b has water. We don’t know whether it has a surface as such, or whether it is basically gaseous. That’s an awful lot not to know before we can start calling these planets “habitable.” Perhaps we anticipate our own strength, to one day make worlds habitable, so long as they can sustain liquid water.
On December 19, an independent, international team of astronomers announced their discovery of a planet in the “hospitable zone” orbiting Tau Ceti, just 12 light years away.
It is tantalyzing having so many planets appearing before our attention as though out of nowhere. It had certainly not been expected that we would be seeing anything like this frequency of planetary formation around stars. Term “fp” of the Drake Equation – “The fraction of those stars with planetary systems” – is quite likely a far greater fraction than Frank Drake expected. It’s fair to say that planetary formation is typical of stars – it’s what they do.
In the background, magnifying the significance of this discovery, is the abundance of water we are finding in space. If anything seemed certain a generation ago, it was that the Moon is an absolute aridity, dust and rock and drier than a biscuit. Now the Moon has water; asteroids have water; even Mercury has water.
It almost seems we’re being invited. Of course Kepler 22b will have water. At Tau Seti there’ll be beer.
The last plank to fall is the biggest. 12 light years is a very great distance, much less 600. One light year is 300,000 times the distance between the Earth and the Sun. Anything less than tens, hundreds of thousands of years is out of the question. These would be multigenerational space colonies. It would mean several thousand people committing themselves to leaving the solar system and embarking upon a 10,000 year journey (let’s be very optimistic about propulsion) to be carried out by 10,000 years of generations content to be born and die in the middle of nowhere.
Don’t hold your breath waiting for that mission. If it were launched, there’d be a decent argument for sending the space police to bust the joint for child endangerment before it could clear the heliopause.
A space colony of that sort would be deciding to leave the solar system and its effectively limitless resources for millenia of barren interstellar space.
Further, it would have been done for naught. One day, possibly not even a century from the time that colony pushed off, a strange craft would appear. A pilot would step out and give the news that we’ve cracked the hyperspace problem.
It’s supposed to be impossible. It isn’t scientifically valid to say this but, personally, I think it’s just a matter of time. If the human race doesn’t devolve into too awful Dark Age or postapocalyptic hellhole – and that’s a big If – it’s hard to see us not figuring out hyperspace sometime in the next few thousand years. Somewhere, a genius will be born who is equal to the occasion. It is inelegant that there should be so many worlds, and so much water, within our sight but forever unreachable. We have people on the job even now. How long before someone breaks through to daylight?
For the time being, the extrasolar planets will be closely observed by generations of space telescopes, starting with the Spitzer Space Telescope that helped the Kepler team spot Kepler 22b.
by Todd Jackson