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By SETH BORENSTEIN, AP Science Writer Seth Borenstein, Ap Science Writer Thu
Nov 13, 6:21 pm ET
WASHINGTON Earth seems to have its first fuzzy photos of alien planets
outside our solar system, images captured by two teams of astronomers. The
pictures show four likely planets that appear as specks of white, nearly
indecipherable except to the most eagle-eyed experts. All are trillions of
miles away three of them orbiting the same star, and the fourth circling a
different star.
None of the four giant gaseous planets are remotely habitable or remotely like
Earth. But they raise the possibility of others more hospitable.
It's only a matter of time before "we get a dot that's blue and Earthlike,"
said astronomer Bruce Macintosh of the Lawrence Livermore National Lab. He led
one of the two teams of photographers.
"It is a step on that road to understand if there are other planets like Earth
and potentially life out there," he said.
Macintosh's team used two ground-based telescopes, while the second team relied
on photos from the 18-year-old Hubble Space Telescope to gather images of the
exoplanets planets that don't circle our sun. The research from both teams
was published in Thursday's online edition of the journal Science.
In the past 13 years, scientists have discovered more than 300 planets outside
our solar system, but they have done so indirectly, by measuring changes in
gravity, speed or light around stars.
NASA's space sciences chief Ed Weiler said the actual photos are important. He
compared it to a hunt for elusive elephants: "For years we've been hearing the
elephants, finding the tracks, seeing the trees knocked down by them, but we've
never been able to snap a picture. Now we have a picture."
In a news conference Thursday, Weiler said this fulfills the last of the major
goals that NASA had for the Hubble telescope before it launched in 1990: "This
is an 18 1/2-year dream come true."
There are disputes about whether these are the first exoplanet photos. Others
have made earlier claims, but those pictures haven't been confirmed as planets
or universally accepted yet. The photos released Thursday are being published
in a scientifically prominent journal, but that still hasn't convinced all the
experts. Alan Boss, an exoplanet expert at the Carnegie Institution of
Washington, and Harvard exoplanet hunter Lisa Kaltenegger both said more study
is needed to confirm these photos are proven planets and not just brown dwarf
stars.
MIT planetary scientist Sara Seager, at the NASA press conference, said earlier
planetary claims "are in a gray area." But these discoveries, "everybody would
agree is a planet," said Seager, who was not part of either planet-finding
team.
The Hubble team this spring compared a 2006 photo to one of the same body taken
by Hubble in 2004. The scientists used that to show that the object orbited a
star and was part of a massive red dust ring which is usually associated with
planets making it less likely to be a dwarf star.
Macintosh's team used ground-based telescopes to spot three other planets
orbiting a different star. That makes it less likely they are a pack of brown
dwarf stars.
The planet discovered by Hubble is one of the smallest exoplanets found yet.
It's somewhere between the size of Neptune and three times bigger than Jupiter.
And it may have a Saturn-like ring.
It circles the star Fomalhaut, pronounced FUM-al-HUT, which is Arabic for
"mouth of the fish." It's in the constellation Piscis Austrinus and is
relatively close by a mere 148 trillion miles away, practically a next-door
neighbor by galactic standards. The planet's temperature is around 260 degrees,
but that's cool by comparison to other exoplanets.
The planet is only about 200 million years old, a baby compared to the more
than 4 billion-year-old planets in our solar system. That's important to
astronomers because they can study what Earth and planets in our solar system
may have been like in their infancy, said Paul Kalas at the University of
California, Berkeley. Kalas led the team using Hubble to discover Fomalhaut's
planet.
One big reason the picture looks fuzzy is that the star Fomalhaut is 100
million times brighter than its planet.
The team led by Macintosh at Lawrence Livermore found its planets a little
earlier, spotting the first one in 2007, but taking extra time to confirm the
trio of planets circling a star in the Pegasus constellation. The star is about
767 trillion miles away, but visible with binoculars. It's called HR 8799, and
the three planets orbiting it are seven to 10 times larger than Jupiter,
Macintosh said.
"I've been doing this for eight years and after eight years we get three at
once," he said.