Title: Dwindle, Dwindle Little Stars --- Hunting for Substellar Objects Young and Old, Rich and Poor
Speaker: Prof. Chen Wen-Ping
(Graduate Institute of Astronomy, National Central University)
Time: 9:00-10:00 June 29th
Venue: Room 717, Science laboratory Building
Abstract： With insufficient masses to sustain core hydrogen fusion, substellar objects continue to cool and fade after birth. Those heavier than 13 jupiter masses, called brown dwarfs, manage to ignite deuterium or lithium, thereby maintaining hydrostatic equilibrium for a short period of time. Those less massive than this do not undertake any nuclear reaction whatsoever in their lives and evolve like planets. So far some 2,000 brown dwarfs and planetary-mass objects are known, almost all in the field, i.e., they are already aged. Characterization of the youngest substellar objects by spectroscopy is hampered by their faintness and often confusion with field contaminations. We describe our international collaboration to select substellar candidates in nearby star-forming regions 1 to 2 Myr old, when brown dwarfs are being formed or in their infancy. Our sample of substellar populations in star clusters, with known ages and distances, provide stringent constraints on theoretical modeling of ultracool atmospheres, and of chromospheric activity. We also present how these least-massive members as the most vulnerable in stellar dynamics to get ejected, leading to eventual disintegration of star clusters.
Speaker：Director of Graduate Institute of Astronomy, National Central University. Got his PhD in 1990, Astronomy, Stony Brook University. Expertise in Multiwavelength Observational Astronomy Star Formation, Young Stellar Objects, Star Clusters, and Brown Dwarfs Stellar Variability; Small Solar-System Objects.