by Tim Sharp
October 16, 2012
from SPACE Website
The sun's closest stellar neighbors are three stars in the Alpha Centauri system.
The two main stars are Alpha Centauri A and Alpha
Centauri B, which form a binary pair. The third star, which may or
may not be part of the system, is Proxima Centauri. It is about 4.22
light-years from Earth and is the closest star other than the sun.
It would take about four years, three months and 18 days to travel there at the speed of light, which is thought to be theoretically impossible (or is it?).
It may be passing through the system and will leave the vicinity in several million years, or it may be gravitationally bound to the binary pair.
If it's bound, it has an orbital period around the
other two of about 500,000 years.
Proxima Centauri is too faint to see unaided,
and through a telescope it appears about four diameters of the full
moon away from the other two.
It is a yellow star of the same type (G2) as the sun, and it is about 25 percent larger. Alpha Centauri B is an orange K2-type star, slightly smaller than the sun. Proxima Centauri is a red dwarf about seven times smaller than the sun, or one-and-a-half times bigger than Jupiter.
All three stars are a bit older - 4.85 billion years old
- than the sun, which is about 4.6 billion years old. (Alpha
Centauri Stars & Planet Explained.)
Its right ascension is
14h 39m 41s and its declination is minus 60 degrees 50 minutes 7
Much of its matter - even more so than the sun - is made up of elements heavier than hydrogen and helium, so there would be plenty of heavier material to make planets from.
And because it is a double-
or triple-star system, the processes that form large gas giant
planets would be suppressed. It would be more likely for the system
to produce terrestrial exoplanets.
The existence of the planet suggests that undiscovered worlds may lurk farther away from its star - perhaps in the habitable zone (below video), that just-right range of distances where liquid water can exist.