47 Ursae Majoris

(The Planet Project)


The circle shows the location of the class G1 star 47 Ursae Majoris (in the constellation Ursa Major). It has not one, but two, planets and thus a planetary system far more like that of our Sun than most of the other stars with planets. The system bears a vague resemblance to our Jupiter and Saturn. The innermost of the two averages 2.1 astronomical units (315 million kilometers, 196 million miles, 1.38 times Mars's distance from the Sun), and has a period of 2.98 years and a minimum mass of 2.4 times that of Jupiter. The outer body orbits nearly twice as far away, at a distance of 3.73 astronomical units (560 million kilometers, 348 million miles, or nearly 75 percent of Jupiter's distance from the Sun) with a period of 7.1 years and a mass at least 0.76 times Jupiter's. The orbit of the inner, larger, planet is somewhat eccentric, and carries the planet as roughly 10 percent closer and farther from the star than average.


47 Ursae Majoris, 46 light years away, is a modest but still-easily visible fifth magnitude (5.10) class G1 hydrogen-fusing dwarf with a temperature almost exactly the same as that of the Sun, 5780 Kelvin. Though the star's mass is about the same as the Sun's, it is 1.5 times as luminous as a result of greater age, estimated to be around 7 billion years. Continuing the solar similarity, 47 Ursae Majoris rotates with a period of 24 days, just slightly less than does the Sun, and has a metal content very much solar, unlike many of the other planet- holding stars. On the other hand, observations show no trace of solar-like sunspot or other activity.

The circle to the right of 47 UMa shows HR 4067 (which lies just down and to the right of Tania Australis), while the one toward the upp right shows Pi-2 UMa (also known as 4 UMa), both of which also support planets.
Written by Jim Kaler. Return to The Planet Project or go to STARS.