July 14, 2005

Planet with three suns challenges astronomers

CAPE CANAVERAL, Fla. (Reuters) - In a scenario out of "Star
Wars," astronomers have detected a planet outside our solar
system with not one, but three suns, a finding that challenges
astronomers' theories of planetary formation.

The planet, a gas giant slightly larger than Jupiter,
orbits the main star of a triple-star system known as HD 188753
in the constellation Cygnus ("The Swan").

The stellar trio and its planet are about 149 light-years
from Earth and about as close to each other as our sun is to
Saturn, U.S. scientists reported on Thursday in the current
edition of the journal Nature.

A light-year is about 6 trillion miles, the distance light
travels in a year.

If you stood on the planet's surface, you would see three
suns in sky, although its orbit centers around the main yellow
star among the trio. The larger of the other two suns would be
orange and the smaller would be red, astronomers at California
Institute of Technology said in a statement.

An artists' rendering of the planet and three stars, as
seen from a hypothetical moon, is available at

The new finding could upset existing theories that planets
usually form out of gas and dust circling a single star, and
could lead scientists to look in new places for planets.

"The implication is that there are more planets out there
than we thought," the commentary said.

Caltech astronomer Maciej Konacki, who wrote the research
article, refers to the new type of planets as "Tatooine
planets," because of the similarity to Luke Skywalker's view of
his home planet by the same name, with its multiple suns, in
the original "Star Wars" film.

The fact that a planet can even exist in a multiple-star
system is amazing in itself, according to Konacki. Binary and
multiple stars are quite common in the solar neighborhood, and
in fact outnumber single stars by some 20 percent.

But so far, most extrasolar planets -- those discovered
outside our planetary system -- have been detected by watching
for a characteristic wobble in the stars their orbit,
reflecting the gravitation pull the planets exert on their

This method is less effective for binary and multiple star
systems, and existing theories said planets were unlikely to
form in this kind of environment.

Konacki found a new way to identify planets by measuring
velocities of all bodies in a binary or multiple star system.