79 Ceti

(The Planet Project)

THE PLANET

The right-hand circle shows the location of the class G star 79 Ceti (in the constellation Cetus). The planet has the lowest (lower limit) mass yet found, 0.22 times that of Jupiter, only 73 percent the mass of Jupiter. The actual mass is likely greater, as the tilt of the orbit is undetermined, but the low lower limit shows the progress that has been made toward finding smaller and smaller planets. The planet orbits 79 Ceti in 76 days (just under Mercury's period around the Sun) in an orbit that averages 0.35 astronomical units from the star (90 percent Mercury's distance from the Sun, 53 million kilometers, or 33 million miles). The orbit is modestly eccentric, the planet going from 0.25 astronomical units at its closest point to 0.45 astronomical units at its farthest.

THE STAR

79 Ceti is a mid-seventh magnitude star (magnitude 6.83) that is just a bit too faint to be seen with the naked eye. Binoculars will bring it out easily, however. It is a class G (G5) subgiant 117 light years away. Though just slightly cooler (about 5700 Kelvin) than the Sun, it is twice as bright, suggesting from theory that it is a solar mass star that is farther along in its ageing process, one about to cease the fusion of hydrogen in its core as it prepares to become a giant (and perhaps destroy its planet).

94 Ceti, toward lower left in the picture, also has an orbiting planet.
Written by Jim Kaler. Return to The Planet Project or go to STARS.