Astronomers using the Gemini North telescope and W.M. Keck Observatory on Hawaii's Mauna Kea, the tallest mountain in the Hawaiian chain, have obtained the first-ever direct images identifying a multi-planet system around a normal star.
The Gemini images allowed the international team to make the initial discovery of two of the planets in the confirmed planetary system with data obtained on Oct. 17, 2007. Then, on Oct. 25, 2007, and in the summer of 2008, the team, led by Christian Marois of the National Research Council of Canada's Herzberg Institute of Astrophysics in Victoria, British Columbia, and members from the U.S. and U.K., confirmed this discovery and found a third planet orbiting even closer to the star with images obtained by the Keck II telescope. These historic infrared images of an extra-solar multiple-planet system were made possible by adaptive optics technology used to correct in real time for atmospheric turbulence, the shimmering or blinking of starlight as it passes through the earth's atmosphere.
"This discovery is significant--it is the first time a family of planets around a normal star outside of our solar system was imaged," said Brian Patten, program manager at the National Science Foundation. "Scientists may now directly view planets themselves, as opposed to indirectly through a star's spectrum or its brightness."
Research results will be published in the Nov.13, 2008, issue of Science Express, an international weekly science journal.
The host star, a young, massive star called HR 8799, is about 130 light years away from Earth. Comparison of multi-epoch data shows that the three planets are all moving with, and orbiting around, the star, proving that they are associated with it rather than just unrelated background objects coincidentally aligned in the image.
The planets, which formed about 60 million years ago, are young enough that they are still glowing from heat released as they contracted, making them easier to see in infrared light. Analysis of the brightness and colors of the objects at multiple wavelengths shows that these objects are about seven and 10 times the mass of Jupiter. As in our solar system, these giant planets orbit in the outer regions of this system--at roughly 25, 40, and 70 times the Earth-Sun separation. The furthest planet orbits just inside a disk of dusty debris, similar to that produced by the comets of the Kuiper Belt objects of our solar system just beyond the orbit of Neptune at 30 times the Earth-Sun distance. In some ways, this planetary system seems to be a scaled-up version of our solar system orbiting a larger and brighter star.
HR 8799 observations are part of a survey of 80 such young, dusty, and massive stars located in the solar neighborhood. The survey is using adaptive optics systems at Gemini, Keck and VLT in Chile to constrain the Jupiter-mass planet populations in a range of separations inaccessible to other exoplanet detection techniques. This discovery was made after observing only a few stars, which may lead to the conclusion that Jupiter-mass planets at separations similar to the giant planets of our solar system are frequent around stars more massive than the Sun, Marois said. "HR 8799's planetary system will be studied in great detail in the years to come, and it will surely be a prime target for future next-generation, exoplanet finding instruments and dedicated space missions."
Source: National Science Foundation