This news release is available in Japanese.
The recently commissioned Gemini Planet Imager has made its first exoplanet discovery: what may be the lowest-mass exoplanet ever directly imaged with a space telescope instrument. Based on available data, the researchers project the planet weighs twice as much as Jupiter - far less than exoplanets directly imaged before, which weighed at least five times Jupiter's mass. The findings from the next-generation Gemini imaging tool pave the way toward a better understanding of how our solar system was formed. In 2013, the Gemini Planet Imager (GPI), a direct exoplanet imaging instrument perched atop Chile's Gemini South Telescope, was deployed. Like other imaging instruments in its class, it was designed to detect planets significantly closer to their parent star, and of significantly lower mass, than any yet found. It is also adept at detecting young planets, which, as they still retain heat from their formation, remain luminous and visible. Using the GPI to study the area around the 20-million-year-old star 51 Eridani, Bruce Macintosh and colleagues found a young planet orbiting at just 13 astronomical units away. By studying its thermal emissions, Macintosh et al. gained insights into its atmospheric composition, which, much like Jupiter's, is dominated by methane (to date, methane signatures have been weak or absent in directly imaged exoplanets). They also say it formed in a similar process to Jupiter. Its unique array of properties suggests it is a "bridge" between hotter planets with wider orbits and those more like Jupiter.
Article #17: "Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager," by B. Macintosh; E.L. Nielsen; K.B. Follette; P. Ingraham; J.-B. Ruffio at Stanford University in Stanford, CA; B. Macintosh; M. Ammons; D.W. Palmer; L.A. Poyneer at Lawrence Livermore National Laboratory in Livermore, CA; J.R. Graham; R.J. De Rosa; J.J. Wang; S. Beckwith; E. Chiang; R.I. Dawson; R. Dong; G. Duchêne; P. Kalas; T. Mittal; M. Salama at University of California, Berkeley in Berkeley, CA. For a complete list of authors, see the manuscript.