A Planet So Light It Would Float on Water
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Astronomers have found a strange new planet which is so puffy it would float on
water.
The new planet, designated HAT-P-1, orbits one member of a pair of distant
stars 450 light-years away in the constellation Lacerta.
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Gaspar Bakos, a Hubble fellow
at the Harvard-Smithsonian
Center for Astrophysics (CfA)
and lead author of a paper
submitted to the Astrophyical
Journal detailing the discovery,
says the planet is lighter than a
giant ball of cork.
"It would float in a bathtub if you
could find a tub big enough to
hold it, " he said.
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Bakos said it's unlike any world
known to science.
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The mysterious planet as seen in this lllustration
by David A. Aguilar (CfA)
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"We could be looking at an entirely new class of planets," he said.
With a radius about 1.38 times Jupiter's, HAT-P-1 is the largest known planet.
In spite of its huge size, its mass is only half that of Jupiter.
HAT-P-1 revolves around its host star every 4.5 days in an orbit one-twentieth of
the distance from Earth to the Sun. Its parent star is one member of a double-
star system called ADS 16402 and is visible in binoculars.
The two stars are separated by about 1500 times the Earth-Sun distance. They
are similar to the Sun but slightly younger - about 3.6 billion years old
compared to the Sun's age of 4.5 billion years.
Although stranger than any other extrasolar planet found so far, HAT-P-1 is not
alone in its low-density status. The first planet ever found to transit its star, HD
209458b, also is puffed up about 20 percent larger than predicted by theory.
HAT-P-1 is 24 percent larger than expected.
"Out of eleven known transiting planets, now not one but two are substantially
bigger and lower in density than theory predicts," said co-author Robert Noyes
(CfA). "We can't dismiss HD209458b as a fluke. This new discovery suggests
something could be missing in our theories of how planets form."
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