This artist's animation illustrates a massive asteroid belt in orbit
around a star the same age and size as our Sun. Evidence for this possible
belt was discovered by NASA's Spitzer Space Telescope when it spotted warm
dust around the star, presumably from asteroids smashing together.
The view starts from outside the belt, where planets like the one shown
here might possibly reside, then moves into to the dusty belt itself. A
collision between two asteroids is depicted near the end of the movie.
Collisions like this replenish the dust in the asteroid belt, making it
detectable to Spitzer.
The alien belt circles a faint, nearby star called HD 69830 located 41
light-years away in the constellation Puppis. Compared to our own solar
system's asteroid belt, this one is larger and closer to its star - it is
25 times as massive, and lies just inside an orbit equivalent to that of
Venus. Our asteroid belt circles between the orbits of Mars and Jupiter.
Because Jupiter acts as an outer wall to our asteroid belt, shepherding
its debris into a series of bands, it is possible that an unseen planet
is likewise marshalling this belt's rubble. Previous observations using
the radial velocity technique did not locate any large gas giant planets,
indicating that any planets present in this system would have to be the
size of Saturn or smaller.
Asteroids are chunks of rock from "failed" planets, which never managed
to coalesce into full-sized planets. Asteroid belts can be thought of as
construction sites that accompany the building of rocky planets.
