A planet about 45 times as massive as Earth is now the fifth in a "family" of confirmed planets orbiting a nearby sunlike star, astronomers announced today at a press briefing.
The discovery marks the first quintuple planetary system ever found—other than our own—and it suggests that systems packed with planets might be much more abundant in the universe than previously believed.
Until now the vast majority of so-called exoplanets found around sunlike stars belonged to single-planet systems.
What's more, huge gaps between the system's planets could mean that there's room for smaller Earthlike worlds to be orbiting in the star's habitable zone.
"This discovery … has me jumping out my socks," said Geoff Marcy, an astronomer at the University of California, Berkeley, and a member of the team that found the new world.
"We now know that our sun and its family of planets is not unusual" in the universe, he added (tour a virtual solar system).
"Architecturally, this new planetary system is reminiscent of our own solar system, albeit souped up—all the new planets are more massive by factors of five or ten."
Messing Up the Math
The star, called 55 Cancri, lies about 41 light-years away in the constellation Cancer. From Earth it is clearly visible with binoculars.
The newfound world—dubbed 55 Cancri f—is the fifth planet found around the star but is the fourth most distant.
Between 1997 and 2004 astronomers had found three exoplanets in the star's habitable zone and one Jupiterlike world much father away.
(Related news: "First Proof of Wet 'Hot Jupiter' Outside Solar System" [July 11, 2007])
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