What’s the Deal with Low-Mass Stars,

Brown Dwarfs, and Planets?

Kelle CruzKelle CruzAmerican Museum of Natural HistoryAmerican Museum of Natural History

People Care About Planets

Low-Mass Stars, BDs, & Jupiter

All about same size as JupiterAll about same size as Jupiter L dwarfs can be either a stellar or sub-stellar.L dwarfs can be either a stellar or sub-stellar. Both planets and brown dwarfs cool over time Both planets and brown dwarfs cool over time

Jupiter was a T dwarf in youthJupiter was a T dwarf in youth

Definition of Planet In the Solar In the Solar

System (low mass)System (low mass) SphericitySphericity Pluto DiameterPluto Diameter Only 9Only 9 Discard altogetherDiscard altogether

Terrestrials, Terrestrials, Jovians, etc.Jovians, etc.

Outside the Solar Outside the Solar System (high mass)System (high mass) Orbits another bodyOrbits another body Formed in circumstellar Formed in circumstellar

disk rather than grav. disk rather than grav. collapsecollapse

Difficult to observeDifficult to observe Deuterium Burning Deuterium Burning

13 M13 MJupiterJupiter cutoff cutoff

Kuiper Belt Objects

Xena (2003 UB313)Xena (2003 UB313) LargerLarger than Pluto (10 than Pluto (10thth Planet?) Planet?) Has a moonHas a moon

2003 EL612003 EL61 Has two moonsHas two moons

2005 FY9 2005 FY9 Both very bright and ¾ Both very bright and ¾

Pluto’s size.Pluto’s size.From Mike Brown’s website.

From Mike Brown’s website.

GQ Lup B Primary Primary

T Tauri (young Sun)T Tauri (young Sun) Secondary (“Planet”)Secondary (“Planet”)

Spectral type: M9-L4Spectral type: M9-L4 Mass: 1-42 MMass: 1-42 MJupiterJupiter

2M 1207B Primary: Primary:

young (8 Myr), activeyoung (8 Myr), active brown dwarf (M8)brown dwarf (M8)

Secondary: Secondary: 5 M5 MJupiter, Jupiter, L5-L9.5 L5-L9.5

Too wide and too Too wide and too massive to have massive to have formed in a formed in a circumstellar disk.circumstellar disk.

In ClosingWhat the heck is a planet?What the heck is a planet?

None of the proposed definitions take care of None of the proposed definitions take care of both mass ends at the same time.both mass ends at the same time.

Personally, I think time will tell but in the Personally, I think time will tell but in the meantime, enjoy the spectacle!meantime, enjoy the spectacle!

Provides a great way to engage the publicProvides a great way to engage the publicSignifies an exciting time in astronomy.Signifies an exciting time in astronomy.