At 25 light years away, Vega is one of the closer stars in the night sky, and one of the brightest. British astronomers, working at the James Clerk Maxwell telescope in Hawaii, have discovered that it possesses a planetary system which is something of a twin to our own.
Vega's system seems to have a gas giant planet about the size of Neptune orbiting at about the same distance as Neptune does from the Sun. This gives Vega plenty of room for smaller, rocky planets to orbit closer in, in what would be Vega's "habitable zone," the "just-right" distance neither too hot (leading to a Venus) nor too cold (leading to a Mars). Just as important, the presence of a gas giant in the outer system means that debris (such as asteroids, comets, and whatnot) tends to get swept up by the larger planet's gravity before it can get deeper into the system, potentially hitting any Earth-like planets.
Earth-like planets can't yet be viewed directly with current astronomical technology, although plans for a so-called "Terrestrial Planet Finder" are in the works. Nearly all of the systems with planets found, however, include gas giants orbiting too close to their stars or in too erratic orbits to allow for the formation of Earth-like planets in the habitable zone. Vega will certainly be on the short list of places for the TPF to check out when it is eventually built.
The more we learn about extra-solar planetary systems, the better we can compare & contrast our own. We're starting to get a good sense now of just how commonplace planetary systems are with the right conditions to allow the formation of planets like Earth: not very, but not impossible to find, either. To me, this is pretty good news. Earth-like planets seem like they will be rare enough that we should really be paying close attention to making sure we don't screw ours up any more than we have, but commonplace enough that, once we get our act together, we could in the far future have new homes among the stars, making sure that a single accident -- or errant asteroid -- doesn't wipe out humanity forever.
I for one think that it is our eventual destiny to spread out through the stars.
But I also think that's centuries away, and we've got an awful lot of work to do on getting our relationship with our homeworld right in the meantime.
As our friend Caroline's fond of saying, "Now, boys, no leaving the planet until you've cleaned up your mess."
These are not mutually exclusive goals. Heading out to the stars is almost certainly more than a century away, but learning more about other planetary systems -- including figuring out just how rare they are, with implications both for encouraging us to be better caretakers of our homeworld and for an eventual human diaspora -- can and should be an ongoing task.
"Now, boys, no leaving the planet until you've cleaned up your mess."
Naahhhh! That's like saying "You can't learn to walk until you're potty trained."
Not only are space exploration and learning housekeeping skills not mutually exclusive, they may be mutually supporting.
RE Vega: Yes, it has a wide habitable zone, but it's also a big, bright, short-lived star that emits lots of UV. Life might never have a chance to get started, or be limited to subsurface microbes. And then in a few hundred million years the Sun goes nova.