US:The discovery by Nasa scientists of a fifth planet circling a star beyond our solar system marks "an exciting next step in the search for worlds like our own", astronomers have said.
The new planet has nearly the same mass and age as our sun, is "easily visible" with binoculars, and is located in a so-called "habitable zone," a band around the star where the temperature would permit liquid water to pool on solid surfaces, Nasa said.
The space agency said the star, 55 Cancri, now holds the record for the number of confirmed extra-solar planets orbiting around it in a system.
Debra Fischer, lead author of a paper that will appear in a future issue of the Astrophysical Journal, said: "This is the first quintuple-planet system.
"This system has a dominant gas giant planet in an orbit similar to our Jupiter. Like the planets orbiting our sun, most of these planets reside in nearly circular orbits." The new planet may be similar to Saturn in its composition and appearance, and completes one orbit every 260 days, a Nasa spokesman said.
Alan Stern, associate administrator for the Science Mission directorate at Nasa HQ in Washington, said: "We are finding solar systems with a richness of planet . . . comparable to our own." Astronomer Geoff Marcy, of the University of California, Berkeley, said the discovery of five extra-solar planets orbiting a star was only one small step. "Earth-like planets are the next destination," he said.