5th planet

5th planet found circling sun-like star

The newly discovered satellite orbiting 55 Cancri, in the constellation Cancer, is more like Saturn than Earth.

Astronomers have discovered a new planet orbiting a sun-like star 41 light-years away, marking the first known planetary quintet outside our solar system.

The newfound planet and four others circle the star 55 Cancri in the constellation Cancer, the researchers said this week. Although it resides in the star's so-called habitable zone, a place where liquid water and mild temperatures should exist, it is more like Saturn than Earth and therefore not likely to support life.

Still, scientists have not ruled out the possibility of finding an Earth-like planet within the system as technology improves.

"It's a system that appears to be packed with planets," said co-discoverer Debra Fischer, an astronomer at San Francisco State University.

The newly discovered planet, the fourth-farthest from 55 Cancri, is about 45 times the mass of Earth and has an orbit of 260 days. It was detected after nearly two decades of observation by ground-based telescopes using the Doppler technique, which measures a planet's stellar wobble.

The other planets in the 55 Cancri system were discovered between 1996 and 2004. The innermost planet is believed to resemble Neptune; the most distant is thought to be Jupiter-like.

Scientists have detected about 250 exoplanets, or planets orbiting a star other than the sun.

The 55 Cancri star holds the record for number of confirmed planets. Only one star is known to have four planets; several others have three or fewer.

The research will appear in a future issue of the Astrophysical Journal. It was funded by NASA, the National Science Foundation and the University of California.

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