The First H-Band Spectrum Of The Giant Planet Beta Pictoris B

Using the recently installed Gemini Planet Imager (GPI), we have obtained the first H-band spectrum of the planetary companion to the nearby young star beta Pictoris. GPI is designed to image and provide low-resolution spectra of Jupiter-sized, self-luminous planetary companions around young nearby stars. These observations were taken covering the H band (1.65 mu m). The spectrum has a resolving power of similar to 45 and demonstrates the distinctive triangular shape of a cool substellar object with low surface gravity. Using atmospheric models, we find an effective temperature of 1600-1700K and a surface gravity of log(g) = 3.5-4.5 (cgs units). These values agree well with "hot-start" predictions from planetary evolution models for a gas giant with mass between 10 and 12 M-Jup and age between 10 and 20 Myr.