First Picture of Likely Planet around Sun-like Star (Forwarded)

Gemini Observatory
Hilo, Hawaii

Science Contacts:

Dr. David Lafreniere
416 978 4971 (office)

Prof. Ray Jayawardhana
416 946 7291 (office)

Prof. Marten van Kerkwijk
416 946 7288 (office)

Media Contacts:

Peter Michaud
Gemini Observatory, Hilo HI
(808) 974-2510 (desk)

Kim Luke
University of Totonto Press Office
(416) 978-4352

First Picture of Likely Planet around Sun-like Star

For Immediate Release: September 15, 2008

Astronomers have unveiled what is likely the first picture of a planet
around a normal star similar to the Sun.

Three University of Toronto scientists used the Gemini North telescope on
Mauna Kea in Hawai'i to take images of the young star 1RXS J160929.1-210524
(which lies about 500 light-years from Earth) and a candidate companion of
that star. They also obtained spectra to confirm the nature of the
companion, which has a mass about eight times that of Jupiter, and lies
roughly 330 times the Earth-Sun distance away from its star. (For
comparison, the most distant planet in our solar system, Neptune, orbits the
Sun at only about 30 times the Earth-Sun distance.) The parent star is
similar in mass to the Sun, but is much younger.

"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 Lafreniere, lead author
of a paper submitted to the Astrophysical Journal Letters and also posted
online. "If we confirm that this object is indeed gravitationally tied to
the star, it will be a major step forward."

Until now, the only planet-like bodies that have been directly imaged
outside of the solar system are either free-floating in space (i.e. not
found around a star), or orbit brown dwarfs, which are dim and make it
easier to detect planetary-mass companions.

The existence of a planetary-mass companion so far from its parent star
comes as a surprise, and poses a challenge to theoretical models of star and
planet formation. "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 Ray Jayawardhana, team member and author of a
forthcoming book on extrasolar planets entitled Worlds Beyond.

The team's Gemini observations took advantage of adaptive optics technology
to dramatically reduce distortions caused by turbulence in Earth's
atmosphere. The near-infrared images and spectra of the suspected planetary
object indicate that it is too cool to be a star or even a more massive
brown dwarf, and that it is young. Taken together, such findings confirm
that it is a very young, very low-mass object at roughly the same distance
from Earth as the star.

Even though the likelihood of a chance alignment between such an object and
a similarly young star is rather small, it will take up to two years to
verify that the star and its likely planet are moving through space
together. "Of course it would be premature to say that the object is
definitely orbiting this star, but the evidence is extremely compelling.
This will be a very intensely studied object for the next few years!" said
Lafreniere.

Team member Marten van Kerkwijk described the group's search method. "We
targeted young stars so that any planetary mass object they hosted would not
have had time to cool, and thus would still be relatively bright," he said.
"This is one reason we were able to see it at all."

The Jupiter-sized body has an estimated temperature of about 1800 Kelvin
(about 1500 C), much hotter than our own Jupiter, which has a temperature of
about 160 Kelvin (-110 C), and its likely host is a young star of type K7
with an estimated mass of about 85% that of the Sun. For more
characteristics of the star and planet see this table from the paper,
http://www.gemini.edu/node/11127

The work that led to this discovery is part of a survey of more than 85
stars in the Upper Scorpius association, a group of young stars formed about
5 million years ago. It uses the Gemini telescope's high-resolution
adaptive optics capabilities to determine the different types of companions
that can form around young stars: stars, brown dwarfs, or planetary mass
objects. "This discovery certainly has us looking forward to what other
surprises nature has in stock for us," said Van Kerkwijk.

The preprint of the paper is available at
http://arxiv.org/abs/0809.1424

IMAGE CAPTIONS:

[Image 1:
http://www.gemini.edu/images/stories...g1_fullres.jpg
(104KB)]
Gemini adaptive optics image of 1RSX J160929.1-210524 and its likely ~8
Jupiter-mass companion (within red circle). This image is a composite of J-,
H- and K-band near-infrared images. All images obtained with the Gemini
Altair adaptive optics system and the Near-Infrared Imager (NIRI) on the
Gemini North telescope. Photo Credit: Gemini Observatory

[Image 2:
http://www.gemini.edu/images/stories...008-6/fig2.gif (45KB)]
Near-infrared spectra of 1RSX J160929.1-210524 and its candidate companion.
The primary's spectrum (row A) is as expected for a temperature of about
4000 K (spectral type K7). The candidate companion's spectrum (black curves
repeated in rows B - F) is compared with the spectra of two young brown
dwarfs (red curves on rows B - C; spectral types M9 and L1) and two older,
cooler brown dwarfs (red curves on rows D - E; L3 and L6. The 'triangular'
shape of the left part of the companion's spectrum is in much better
agreement with the two young brown dwarfs, indicating the candidate
companion has low gravity; in turn, this implies it has not yet fully
contracted and thus is still young. The companion spectrum and those of all
comparison objects have been normalised to be the same on the right-hand
side. The fact that, compared to the young brown dwarfs, the candidate
companion is slightly fainter in the left-hand part **indicates that it it
is cooler**, more like the field L3 brown dwarf. The comparison with models
(row F) confirms that the companion has low gravity, and thus is young.