ASTRONOMERS have finally spied a planetary system that looks something like
our own.
Most of the 70 known “exoplanets”—gas giants with orbits that are
either highly elliptical or very close to their stars—are nothing like
Earth. But in 1996, a planet 2.5 times the mass of Jupiter was found in a
circular 2.99-year orbit around the star 47 Ursae Majoris.
Now researchers have found a smaller sibling in a circular orbit around the
same star. The new planet has about three-quarters the mass of Jupiter, so the
pair have the same relative masses as Saturn and Jupiter
(www.exoplanets.org…
