GeminiFocus 2015 Year in Review | Page 9

October 2015 Julien Rameau and Robert De Rosa GPI Discovers the Most Jupiter-like Exoplanet Ever Directly Detected After 10 years of development, the Gemini Planet Imager (GPI) — the most powerful of its kind — started operating routinely in late 2013. After observing just 44 stars, GPI found its first exoplanet — a young, cool object that is the most Jupiter-like, and probably the lowest-mass exoplanet, ever directly imaged. This finding will also lead to a better understanding of how our Solar System formed. Detecting an extrasolar planet directly from its infrared radiation is extremely challenging. This is mainly due to two factors: (1) the large contrast in brightness between the star and planet (around a million to one), and (2) the small angular separation between the star and planet (under one arcsecond). Moreover, the Earth’s turbulent atmosphere strongly degrades the image quality, preventing large ground-based telescopes from reaching their theoretical diffraction limit. To overcome this detrimental effect, many world-class observatories, like Gemini, employ high-angular resolution instruments with adaptive optics (AO) systems to both sense, and correct for, wavefront distortions, producing extremely sharp images free from atmospheric distortions. The first generation of AO-fed instruments discovered a handful of extrasolar planets with contrasts of ~105, or at angular separations greater than one arcsecond. To detect fainter, lessmassive planets closer to their parent star (probing scales similar to our own Solar System), an international team of astronomers and engineers conceived, designed, and built the most powerful AO instrument to date: the Gemini Planet Imager (GPI) on the Gemini South telescope in Chile. January 2016 2015 Year in Review GeminiFocus 7