Whats the Deal with LowMass Stars Brown Dwarfs

What’s the Deal with Low-Mass Stars, Brown Dwarfs, and Planets? Kelle Cruz American Museum of Natural History

People Care About Planets

Low-Mass Stars, BDs, & Jupiter l l l All about same size as Jupiter L dwarfs can be either a stellar or sub-stellar. Both planets and brown dwarfs cool over time l Jupiter was a T dwarf in youth

Definition of Planet l In the Solar System (low mass) l l Sphericity Pluto Diameter Only 9 Discard altogether l Terrestrials, Jovians, etc. l Outside the Solar System (high mass) l l Orbits another body Formed in circumstellar disk rather than grav. collapse l l Difficult to observe Deuterium Burning l 13 MJupiter cutoff

Kuiper Belt Objects l Xena (2003 UB 313) l l Larger than Pluto (10 th Planet? ) Has a moon From Mike Brown’s website. l 2003 EL 61 l l l Has two moons 2005 FY 9 Both very bright and ¾ Pluto’s size. From Mike Brown’s website.

GQ Lup B l Primary l l T Tauri (young Sun) Secondary (“Planet”) l l Spectral type: M 9 -L 4 Mass: 1 -42 MJupiter

2 M 1207 B l Primary: l l l Secondary: l l young (8 Myr), active brown dwarf (M 8) 5 MJupiter, L 5 -L 9. 5 Too wide and too massive to have formed in a circumstellar disk.

In Closing l What the heck is a planet? l None of the proposed definitions take care of both mass ends at the same time. l Personally, I think time will tell but in the meantime, enjoy the spectacle! Provides a great way to engage the public l Signifies an exciting time in astronomy. l