* Astronomy

1RXS J160929.1-210524 b, a directly imaged exoplanet was announced on 8 September 2008
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A planet-like object about eight times the size of Jupiter is locked in orbit around very young star, though the exact relationship between the two remains a mystery.
Circling 300 times farther from the star than Earth orbits the sun, the object could be a planet, perhaps one that was catapulted out into the nether regions after a collision or close encounter with an as-yet undetected sibling planet.
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First directly imaged planet confirmed around Sun-like star.

A planet only about eight times the mass of Jupiter has been confirmed orbiting a Sun-like star at over 300 times farther from the star than the Earth is from our Sun. The newly confirmed planet is the least massive planet known to orbit at such a great distance from its host star. The discovery utilised high-resolution adaptive optics technology at the Gemini Observatory to take direct images and spectra of the planet.
First reported in September 2008 by a team led by David Lafrenière (then at the University of Toronto, now at the University of Montreal and Centre for Research in Astrophysics of Quebec), the suspected planetary system required further observations over time to confirm that the planet and star were indeed moving through space together.
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Title: The Directly Imaged Planet around the Young Solar Analogue 1RXS J160929.1-210524: Confirmation of Common Proper Motion, Temperature and Mass
Authors: David Lafrenière (U. Montréal), Ray Jayawardhana (U. Toronto), Marten H. van Kerkwijk (U. Toronto)

Giant planets are usually thought to form within a few tens of AU of their host stars, and hence it came as a surprise when we found what appeared to be a planetary mass (~0.008 Msun) companion around the 5 Myr-old solar mass star 1RXS J160929.1-210524 in the Upper Scorpius association. At the time, we took the object's membership in Upper Scorpius -- established from near-infrared, H- and K-band spectroscopy -- and its proximity (2.2", or 330 AU) to the primary as strong evidence for companionship, but could not verify their common proper motion. Here, we present follow-up astrometric measurements that confirm that the companion is indeed co-moving with the primary star, which we interpret as evidence that it is a truly bound planetary mass companion. We also present new J-band spectroscopy and 3.0-3.8 microns photometry of the companion. Based on a comparison with model spectra, these new measurements are consistent with the previous estimate of the companion effective temperature of 1800±200 K. We present a new estimate of the companion mass based on evolution models and the calculated bolometric luminosity of the companion; we obtain a value of 0.008 (-0.002/+0.003) Msun, again consistent with our previous result. Finally, we present angular differential imaging observations of the system allowing us to rule out additional planets in the system more massive than 1, 2 and 8 Mjup at projected separations larger than 3" (~440 AU), 0.7" (~100 AU) and 0.35" (~50 AU), respectively. This companion is the least massive known to date at such a large orbital distance; it shows that objects in the planetary mass range exist at orbital separations of several hundred AU, posing a serious challenge for current formation models.

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