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Dusty Disc May Mean Other Earths
DoraLives writes "According to the BBC, astronomers say they have evidence for Earth-like planets orbiting a nearby star. The star in question is Vega, which is nice and close (as stars go), quite young (also as stars go), and one of the brightest stars in the sky. Apparently, 'Vega has a disc of dust circling it, and at least one large planet which could sweep debris aside allowing smaller worlds like Earth to exist.' Should be interesting to keep an eye on it as the years roll by as the disk rotates and our optical powers keep growing."
-Since the Vega system is very young, any terrestrial planets will probably not yet be in a "finished" state, but will still be busy accreting smaller planetesimals- for the Earth, this initial process might have taken 30 million years. Also, any such planets will not have finished differentiating into a core, a mantle and a crust.
If you send a probe there, it will not be able to find a cool surface on any of the larger planetesimals (growing proto-planets).
The Vega system is interesting because it provides a snapshot of the early phase of planet formation.
If you want to make a "Star Trek" style tour of a system, landing on the planets and checking for the presence of life, you need to find a more "mature" system, where the planetary crusts have had time to cool off, and where most of the orbiting debris has alredy been swept up by planets.
One other interesting point about the Vega system though: It is bound to have an amazing number of large, highly visible comets ! In mature systems, most comets have either been kicked out to the Oort cloud or crashed into a planet.
Yours Birger Johansson Sweden
By Earthlike I believe they mean terrestrial; a rocky world, as opposed to a gas giant.
Other known terrestrial worlds include baked-out Mercury, greenhouse-wracked Venus, and dry, cold Mars. Most people would not consider these "Earthlike" in the Star Trek Class M sense of the word.
That said: Even given the existence of terrestrial planets, Vega isn't a great place to go looking for a habitable, life-bearing world. It's a bright, hot star, which also means that it is a short-lived star. In a few hundred million years, when its potential planets begin to cool to the point where water would condense, Vega would be getting ready to wander off the main sequence and get way unpleasant to be near.
Another strike against life developing on Vega worlds: a greater percentage of its energy output would be in "bluer" wavelengths, including UV. Once it got started, life might adapt to UV, but to get started in the first place it needs some stability. I can see a influx of UV ripping apart delicate chemical chains in Vega Prime's oceans, greatly reducing the chance that life would get a foothold.
All this said, this is hopeful news, because the existence of one planet-forming debris field means there are probably others . . . some around more genial F and G and K class stars.
Stefan