- (Reuters) -- Astronomers have detected a planet with
not one, but three suns, a finding that challenges astronomers' theories
of planetary formation.
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- 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").
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- 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, US
scientists report in the journal Nature.
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- A light-year is about 10-trillion kilometres, the distance
light travels in a year.
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- If you stood on the planet's surface, you would see three
suns in sky, although its orbit centres around the main yellow star among
the trio.
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- 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.
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- 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.
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- "The implication is that there are more planets
out there than we thought," the commentary said.
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- Caltech astronomer Dr 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.
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- The fact that a planet can even exist in a multiple-star
system is amazing in itself, he said.
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- Binary and multiple stars are quite common in the solar
neighbourhood, and in fact outnumber single stars by some 20 per cent.
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- 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 suns.
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- 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.
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- Dr Konacki found a new way to identify planets by measuring
velocities of all bodies in a binary or multiple star system
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- An artists' rendering of the planet and three stars,
as seen from a hypothetical moon, is available at http://pr.caltech.edu/media/trinary_sunset_small-1.jpg.
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- © 2005 ABC
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- http://www.abc.net.au/news/newsitems/200507/s1414775.htm
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