K Dwarf Planets

Many searches for planets in other star systems look for stars like the Sun. Since the Sun is the only star that’s known to harbor life, that makes sense.

But Sun-like stars are pretty rare. So some searches are taking aim at stars in the next category down — stars that are a little smaller, lighter, and fainter than the Sun. They’re known as K dwarfs. They’re in the prime of life. And they can stay in that phase for tens of billions of years — much longer than the total lifespan of the Sun. That means there’s plenty of time for life to take hold in such systems.

And the systems should be good homes for life. The stars are pretty stable, and they don’t produce a lot of damaging radiation. And they’re good targets for planet hunts because habitable worlds are likely to be fairly close to their stars, making them easier to find.

Astronomers have mapped about 5,000 K dwarfs within 50 parsecs of Earth — about 165 light-years. A few dozen of them have confirmed planets. But none of the planets is like Earth, or in the right place for Earth-like life.

A double K-dwarf system is high in the sky at nightfall, less than 12 light-years away. It’s close to Deneb, the bright tail of Cygnus, the swan. The system’s two stars are far apart, so there’s plenty of room for planets. So far, though, no planets have been found — prime real estate with no tenants.

Tomorrow: the brilliant “morning star” stands high.
 

Script by Damond Benningfield