Astronomers have taken what may the first picture of a planet
orbiting a star similar to the sun.
This distant world is giant (about eight times the mass of
Jupiter) and lies far out from its star (about 330 times the Earth-Sun distance).
But for all the planet's strangeness, its star is quite like our own sun.
Previously, the only photographed
extrasolar planets have belonged to tiny, dim stars known as brown dwarfs. And
while hundreds
of exoplanets have been detected by noting their gravitational tug on their
parent stars, it is rare to find one large enough to image directly.
"This is the first time we have directly seen a
planetary mass object in a likely orbit around a star like our sun," said
David Lafrenière, an astronomer at the University of Toronto who led the team
that discovered the star. "If we confirm that this object is indeed
gravitationally tied to the star, it will be a major step forward."
Further study will be needed to prove that the planet is in
fact orbiting around the star, as opposed to the possibility, however unlikely,
that the two objects just happen to lie in the same area of the sky at roughly
the same distance from us.
"Of course it would be premature to say that the object
is definitely orbiting this star, but the evidence is extremely
compelling," Lafrenière said. "This will be a very intensely studied
object for the next few years!"
The researchers used the Gemini North telescope on Mauna Kea in Hawaii to glimpse the planet and its star, 1RXS J160929.1-210524, which lies
about 500 light-years from Earth. Though the star has about 85 percent the mass
of the sun, it is younger than our star. In order to image the far-flung
system, the team utilized adaptive optics technology, which uses flexible
mirrors to offset the distortion light suffers as it passes through Earth's
atmosphere.
The strange planet so far from its parent star is unexpected
based on current theories of star and planet formation. For comparison, the
farthest planet in our solar system, Neptune, lies only 30 times the Earth-sun
distance away from the sun.
"This discovery is yet another reminder of the truly
remarkable diversity of worlds out there, and it's a strong hint that nature
may have more than one mechanism for producing planetary mass companions to
normal stars," said team member Ray Jayawardhana, also of the University of Toronto.
The distant exoplanet, at about 1,800 Kelvin (about 1,500ºC),
is also much hotter than our own Jupiter, which has a temperature of about 160
Kelvin (-110ºC).
The team discovered the new planet as part a survey of more
than 85 stars in the Upper Scorpius association, a group of young stars formed
about 5 million years ago. The researchers have detailed the study in a
paper submitted to the Astrophysical Journal Letters and also posted
online.
"This discovery certainly has us looking forward to
what other
surprises nature has in stock for us," said University of Toronto team member Marten van Kerkwijk.