There's another solar system like ours, and it's very close by.
Researchers from the University of California at Berkeley and the Carnegie Institution announced Thursday that they've found the first planetary system that closely resembles our own.
The system centers around the sun-like star 55 Cancri, which lies in the Cancer constellation, only 41 light years away. Just around the corner, in astronomical terms.
"It's not quite a sibling to our solar system," said the Carnegie Institution's Paul Butler, one of the primary researchers. But 55 Cancri is like "a first cousin."
Since 1995, scientists have discovered about 80 planets outside of our solar system. But none of these "extrasolar" planets really looked like any of the ones in our backyard; they orbited too close to their stars, mostly making elongated, uneven rotations.
Butler and colleague Geoffrey Marcy, from Berkeley, said a gas giant circling 55 Cancri is the first extrasolar analogous to one of our planets, with an orbit that's very similar to Jupiter's.
The newfound planet, one of 15 announced Thursday by Marcy and Butler, orbits at 5.5 AU (short for "astronomical unit," or the 93-million mile distance between the Earth and the sun) from its star. That's extremely close to Jupiter's distance from our own sun: 5.2 AU, or 512 million miles.
The planet's slightly elongated orbit takes it around the star in about 13 years, comparable to Jupiter's orbital period of 11.86 years. It is 3.5 to 5 times the mass of Jupiter.
Marcy and Butler said they have detected two other planets in the system. One is about 0.1 AU away, with a mass that's 90 percent of Jupiter's, revolving around 55 Cancri every 14.6 days. The other has about a quarter of Jupiter's mass and orbits 55 Cancri every 44.3 days at a distance of .25 AU.
An Earth-like planet with a stable orbit could lie between these two inner planets and the Jupiter-esque outer planet, Marcy added, although there's no way to tell at the moment.
Marcy and Butler found these planets using the same technique they've long employed for discovering new worlds (the two are credited with locating more than half of the known extrasolar planets). Orbiting planets cause their stars to wobble, ever so slightly; 55 Cancri's "Jupiter," for instance, causes the star to move about 55 meters per second. The wobble produces a small change in the wavelength of a star's light.
This is called a Doppler shift, and by measuring it, March and Butler have been able to infer where circling planets are, and how much they weigh.
Researchers are unable to actually see any extrasolar planets directly. But 55 Cancri is near enough that, when NASA's Terrestrial Planet Finder mission launches next decade, it is "quite likely that we'll be able to get a direct image of its planet," said David Spergel, a Princeton astrophysics professor. "It's [also] a very interesting target to look for life."
55 Cancri is one of 2,000 stars -- all within 150 light years -- that Butler and Marcy are surveying using their Doppler-shift analysis.
"We're hoping to be in a position in about 10 years or so to know how common systems like ours are," Butler said. They began their search in 1984.
The finding of such a sytem so close to our own, Marcy said, "begs the question: 'Are there other Earths?'"
"There must be billions of planetary systems somewhat like our own in the Milky Way."
Ref: Wired.com
Another Solar System
