A group of European-led
astronomers has made a photograph of what appears to be a planet orbiting another
star. If so, it would be the first confirmed picture of a world beyond our solar
system.
"Although it is surely much
bigger than a terrestrial-size object [like Earth], it is a strange feeling
that it may indeed be the first planetary system beyond our own ever imaged,"
said Christophe Dumas, an astronomer at the European Southern Observatory.
SPACE.com revealed
a similar
imaging effort of another planet candidate in May by a U.S.-led team that
used the Hubble Space Telescope. That possible planet has not been confirmed
and could be a dim star in the background of the picture.
Otherwise, all of the more
than 120 known extrasolar planets have been detected indirectly, by noting the
shadow of a planet crossing in front of a star or a planet's gravitational effect
on a star. Because planets are so dim compared to stars, technology has not
been able to spot them amid stellar glare.
That is, perhaps, until
now.
Young planet
The new picture shows a
dim, red point of light that Dumas and his colleagues think is a young, giant
planet something like Jupiter. It orbits a failed star known as a brown dwarf,
a very dim type of star -- its core does not support nuclear fusion -- that
astronomers have for years hoped would make for good planet hunting.
The brown dwarf, catalogued
as 2M1207 and just 8 million years old, is 42 times less massive than the Sun,
or some 25 times heftier than Jupiter.
The setup is 230 light-years
away.
The possible planet is about
five times as massive as Jupiter, the observations show. An analysis of its
emissions found it contains water, which suggests its mass is in the range of
planets rather than stars, the researchers announced today.
The object is still contracting
into its final form and so is very warm, some 1,830 degrees Fahrenheit (1,000
Celsius), according to the research team, which was led by ESO's Gael Chauvin.
The photograph was made
at ESO's Paranal Observatory in Chile with an infrared camera, which records
heat rather than visible light. A system of adaptive optics on the Very Large
Telescope (it's 27 feet wide, or 8.2 meters) corrects for blurring effects of
Earth's atmosphere, making detailed observations possible.
The discovery will be detailed
in the journal Astronomy & Astrophysics.
If it is a planet, the object
orbits 55 times farther from the brown dwarf than Earth is from the Sun, or
roughly twice the Earth-to-Neptune distance.
One remaining question,
however, is whether the thing might instead be a star that's in the foreground
or background and not gravitationally bound to the brown dwarf, a scenario the
researchers say is "statistically very improbable."
Additional observations
to monitor the movement of the two objects will reveal the answer within two
years, the astronomers say.
How it formed
In separate work, Ray Jayawardhana
of the University of Toronto has been studying the brown dwarf in question,
2M1207.
He agrees that the newfound object is most likely in orbit around the brown
dwarf. It could be a very dim brown dwarf in the foreground, he said, but that's
doubtful.
The water found in the atmosphere,
in the form of steam, "means it would have to be pretty cool and couldn't
possibly be a star," Jayawardhana told SPACE.com.
Jayawardhana's team found
that 2M1207,
like a real star, has a surrounding disk of hydrogen gas, the leftovers of the
brown dwarf's formation. But in contrast to how planets probably developed in
our solar system, he does not think the planet was born out of the brown dwarf's
disk. Instead, the planet and brown dwarf likely "formed together out of
a clump of gas and dust," he said.
Another unsettled issue
is whether an object of five Jovian masses is truly a planet. Some astronomers
put the upper limit for planetary mass at 13 times what's in Jupiter. Others
argue that a planet is must orbit a star and have formed out of its leftovers.
There is no
official definition for the term "planet."
Jayawardhana doesn't care
what the new object is called, it is still very interesting from a physics perspective.
"This discovery opens up
a whole new regime of objects for us to look at and learn about," he said.
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