Astronomers have detected a Jupiter-size planet orbiting the star 47 Ursae Majoris, located in the Big Dipper. The second planet to be found circling the nearby star, this discovery reveals the first evidence yet of a planetary system akin to our own. A report on the new findings, which were announced yesterday, has been submitted to the Astrophysical Journal.

Geoffrey Marcy and Debra Fischer of the University of California at Berkeley and their colleagues found the planet using telescopes at the University of California's Lick Observatory to measure so-called Doppler-shifted light from stars. The same general technique showed the researchers the first planet, but only with improved precision have they been able to detect this smaller one.

Located a mere 51 light-years from Earth, the star around which these two planets travel is a yellow star similar to our sun. Importantly, these planets are in circular orbitsa rarity among the extrasolar planets known thus far. The newly discovered system also resembles our solar system in that the mass ratio of the large inner planet to the smaller outer planet orbiting 47 Ursae Majoris is the same as the mass ratio of Jupiter to Saturn: 3.3.

"When we discovered the first planet around 47 Ursae Majoris five years ago, I never dreamed that we would find yet another planet orbiting the same star. Every new planetary system reveals some new quirk that we didn't expect. We've found planets in small orbits and wacky eccentric orbits," Marcy remarks. "With 47 Ursae Majoris, it's heartwarming to find a planetary system that finally reminds us of our solar system."