Monday, June 4, 2012
Cahill, Hameetman Auditorium
Astronomy Tea Talk
Observations of Terrestrial Planet Formation
Carl Melis, UCSD
We are conducting a survey to identify stars that are orbited by copious amounts of warm dust at terrestrial planet-like separations. We argue that these dusty systems are the result of recent giant impacts between rocky planetary embryos or planets orbiting in the stars' terrestrial planet-zone and hence are a tell-tale sign of the final stages of terrestrial planet formation. Some systems identified in our search challenge our understanding of the rocky planet formation process, including two stars that could potentially host carbon-dominated rocky planets, a star whose intense terrestrial planet-zone disk emission disappeared on a few year timescale, and a star that hosts sufficient terrestrial planet zone dust to intercept 17% of the incoming stellar light. Synthesis of all stars with evidence for terrestrial planet-zone dust allows us to identify the age range during which terrestrial planets undergo final mass accretion through giant impacts. For stars of roughly Solar mass, we find this age range to be between 30 and 100 Myr while for stars a few times the mass of the Sun we find this age range to be between 10 and 20 Myr. For both groups we find that terrestrial planets are likely common (roughly one terrestrial planet for every star).