FIRST PICTURE OF LIKELY PLANET AROUND SUN-LIKE STAR

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 (8) 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 Lafrenicre, 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 Lafrenicre.

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 deg C), much hotter than our own Jupiter, which has a temperature of about 160 Kelvin (-110 deg C), and its likely host is a young star of type K7 with an estimated mass of about 85% that of the Sun.

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

A full-resolution image of the star and planet are available at: www.gemini.edu/sunstarplanet

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located at Mauna Kea, Hawai'i (Gemini North) and the other telescope at Cerro Pachon in central Chile (Gemini South), and hence provide full coverage of both hemispheres of the sky. Both telescopes incorporate new technologies that allow large, relatively thin mirrors under active control to collect and focus both optical and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in each partner country with state-of-the-art astronomical facilities that allocate observing time in proportion to each country's contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the UK Science and Technology  Facilities Council (STFC), the Canadian National Research Council (NRC), the Chilean Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT), the Australian Research Council (ARC), the Argentinean
Consejo Nacional de Investigaciones Científicas y Tecnicas (CONICET) and the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnologico CNPq). The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

FOR MORE INFORMATION:

Science Contacts:
    * Dr. David Lafrenière
      1-416 978 4971 (office)
lafreniere@astro.utoronto.ca

    * Prof. Ray Jayawardhana
      1-416 946 7291 (office)
rayjay@astro.utoronto.ca

    * Prof. Marten van Kerkwijk
      1-416 946 7288 (office)
mhvk@astro.utoronto.ca

Media Contacts:
    * Peter Michaud
      Gemini Observatory, Hilo HI
      1-808-974-2510 (desk)
      1-808-936-6643 (cell)
pmichaud@gemini.edu

    * Kim Luke
      University of Toronto Press Office
      1-416-978-4352      
kiml@artsci.utoronto.ca