GeminiFocus July 2017 | Page 14

Peter Michaud Science Highlights Gemini Planet Imager observations of exoplanet 51 Eridani b help support cold-start giant planet formation; GeMS-GSAOI data on the proper motion of stars in the Pyxis globular cluster set a lower limit for the Milky Way’s mass of 950 million Suns; and finally, Gemini Multi-Object Spectrograph (GMOS) data from Gemini North help to characterize the active fragmented asteroid P/2010 A2. GPI Data Hint at Cold-Start Giant Planet Formation Figure 1. New research on the first exoplanet dis- covered using the Gemini Planet Imager (GPI) — 51 Eridani b — hints that it may have formed by the collapse of icy disk materials followed by the accretion of a thick gas atmosphere, much like that de- scribed in the cold-start model. GPI images in the K1, K2, LP, and MS bands; the emission of the host star was blocked. The exoplanet 51 Eri b is indicated by an arrow. Located about 100 light years from Earth, Exoplanet 51 Eri b is between 2–10 times the mass of Jupiter. Two main scenarios of giant planet forma- tion exist: hot start and cold start. In the hot-start model, gas giants form directly via the rapid collapse of a gaseous proto- planetary disk. In the cold-start scenario, a gas-giant begins as a core that forms very early on from planetesimal agglom- erations before collecting the plentiful gas around it. 12 GeminiFocus July 2017