Kappa Coronae Borealis

(The Planet Project)

Kappa Corona Borealis used to be a much hotter class A star, showing that such stars -- which are more massive than the Sun and frequently have surrounding debris disks -- also have real planets to go along with them.

THE PLANET

The upper circle shows the location of the class K subgiant Kappa Coronae Borealis (in the constellation Corona Borealis). The planet orbits Rho Coronae Borealis in 1191 days (3.26 years) and is and is 2.7 Astronomical Units from the star (which would place it nicely within our asteroid belt 1.8 times farther than Mars is from the Sun). Since we do not know the orbital tilt, we can measure only a lower limit to the planet's mass, which is at least 1.8 times that of Jupiter.

THE STAR

Kappa Coronae Borealis is a fifth magnitude (4.82) class K (K1) subgiant 102 light years away with a temperature of 4960 Kelvin, a luminosity 14 times solar, and a mass 1.8 times that of the Sun. As a subgiant, it has given up core hydrogen fusion, is just beginning to evolve into a true giant with a current radius 5 times that of our Sun. Though the star will eventually grow in size to near that of the Earth's orbit, its large planet will still be far enough away to escape destruction.

Rho Coronae Borealis, the lower star in the picture, also has an orbiting planet.
Written by Jim Kaler. Return to The Planet Project or go to STARS.