* Astronomy

Astronomers who have been anxiously keeping an eye on the red dwarf star Gliese 581, in the hope of observing the Earth like planet Gliese 581c, pass between the Earth and its host star, have so far met with disappointment.
The star's light, as viewed by the Canadian Space Agency's MOST space satellite, has remained constant, meaning the planet has not made its transit, researchers say.

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Title: Hot Jupiters in binary star systems
Authors: Yanqin Wu, Norman W. Murray, J. Michael Ramsahi

Radial velocity surveys find Jupiter mass planets with semi-major axes (a) less than 0.1 AU around 1.2% of solar-type stars; counting planets with a as large as 5 AU, the fraction of stars having planets reaches 7%. An examination of the distribution of semi-major axes shows that there is a clear excess of planets with orbital periods around 3 or 4 days, corresponding to a ~ 0.03 AU, with a sharp cut-off at shorter periods. It is believed that Jupiter mass planets form at large distances from their parent stars; some fraction then migrate in to produce the short period objects. We argue that a significant fraction of the `hot Jupiters' (a<0.1 AU) may arise in binary star systems in which the orbit of the binary is highly inclined to the orbit of the planet. Mutual torques between the two orbits drive down the minimum separation or periapse r_p between the planet and its host star (the Kozai mechanism). This periapse collapse is halted when tidal friction on the planet circularises the orbit faster than Kozai torque can excite it. The same friction then circularises the planet orbit, producing hot Jupiters with the peak of the semimajor axis distribution lying around 3 days. For the observed distributions of binary separation, eccentricity and mass ratio, roughly 2.5% of planets with initial semimajor axis a ~ 5 AU will migrate to within 0.1 AU of their parent star.

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Title: The Gemini Deep Planet Survey -- GDPS
Authors: David Lafreniere, Rene Doyon, Christian Marois, Daniel Nadeau, Ben R. Oppenheimer, Patrick F. Roche, Francois Rigaut, James R. Graham, Ray Jayawardhana, Doug Johnstone, Paul G. Kalas, Bruce Macintosh, Rene Racine

We present the results of the Gemini Deep Planet Survey, a near-infrared adaptive optics search for giant planets and brown dwarfs around nearby young stars. The observations were obtained with the Altair adaptive optics system at the Gemini North telescope and angular differential imaging was used to suppress the speckle noise of the central star. Detection limits for the 85 stars observed are presented, along with a list of all faint point sources detected around them. Typically, the observations are sensitive to angular separations beyond 0.5" with 5-sigma contrast sensitivities in magnitude difference at 1.6 micron of 9.6 at 0.5", 12.9 at 1", 15 at 2", and 16.6 at 5". For the typical target of the survey, a 100 Myr old K0 star located 22 pc from the Sun, the observations are sensitive enough to detect planets more massive than 2 Mjup with a projected separation in the range 40-200 AU. Second epoch observations of 48 stars with candidates (out of 54) have confirmed that all candidates are unrelated background stars. A detailed statistical analysis of the survey results is presented. Assuming a planet mass distribution dN/dm ~ m^{-1.2} and a semi-major axis distribution dN/da ~ a^{-1}, the upper limits on the fraction of stars with at least one planet of mass 0.5-13 Mjup are 0.29 for the range 10-25 AU, 0.13 for 25-50 AU, and 0.09 for 50-250 AU, with a 95% confidence level. Without making any assumption on the mass and semi-major axis distributions, the fraction of stars with at least one brown dwarf companion having a semi-major axis in the range 25-200 AU is 0.018_{-0.014}^{+0.078}, with a 95% confidence level. The observations made as part of this survey have resolved the stars HD 14802, HD 135363, HD 160934, HD 166181, and HD 213845 into close binaries for the first time.

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Our galaxy may teem with rogue giant planets that were ejected from young solar systems, according to a new theoretical study presented here at the 210th meeting of the American Astronomical Society. The number of homeless planets drifting through interstellar space may actually exceed the number of planets orbiting stars.
The rogue giants are part of a possible solution to a long-standing mystery. Most giant planets in other solar systems are in elliptical orbits, unlike the almost circular paths of Jupiter, Saturn, Uranus, and Neptune. No one knows why. Now, theoretical astrophysicists Mario Juri and Scott Tremaine of the Institute for Advanced Study in Princeton, New Jersey, suggest a possible explanation.

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