Transcript Exoplanets and Brown Dwarfs - Astronomy Program

Extrasolar Planets and Brown Dwarfs
James Liebert
Steward Observatory
University of Arizona
Tucson, AZ
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
Extrasolar Planets: Planets found around other stars usually similar to our Sun
and
Brown dwarfs: entities between the size (mass) of many Jupiters
and low mass stars
Definition of a star: a gravitationally-bound sphere of gas massive
enough to fuse hydrogen into helium, thereby providing the energy
to shine
In units of the mass of the Sun
2 x 1033 gm = 2 x 1030 kg = 1M
Jupiter is very close to 0.001 M
Jovian planets defined to be up to 13 MJ (0.013 M)
Brown dwarfs 0.013 - 0.075 M
Hydrogen fusion requires a mass of 0.075M (75MJ)
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Brown is not a color
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QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
McDonald Observatory workshop
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
McDonald Observatory workshop
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
Binary stars: Each orbits the common center of mass
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
McDonald Observatory workshop
LHS 4033
Most Massive
Well Measured
White Dwarf
1.31-1.335M
10,900 K
0.0037R
Dahn, Bergeron, Liebert,
Harris, Canzian, Leggett,
And Boudreault
2004 ApJ, 605, 400
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McDonald Observatory workshop
J. Davy Kirkpatrick -- Annual Reviews of Astronomy and Astrophysics
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J. Davy Kirkpatrick -- “Inventor” of the L Dwarf Classification System
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Adam Burgasser: Definer of T Dwarfs and National Collegiate Diving Champion
(U. California, San Diego)
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Modelling a T6.5 emission Dwarf Infrared Spectrum (Liebert and Burgasser 2007 ApJ,655,522)
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McDonald Observatory workshop
Dispersion in infrared colors
At a given spectral type
Variable dust layers in L ‘s
Open circles: subdwarfs
(lower [Fe/H])
also higher gravity
Open triangles: young and
low gravity
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Temperatures from Luminosities
(via trig parallaxes)
and Radii
Teff ~ (L / 4πR2)1/4 1/4
R = constant ~ Rjup
Declining Teff as brown dwarf
cools with time
Small temperature change from
L6 -- T5 means
Rapid evolution through these
Spectral types
Infrared types not as cleanly
Monotonic with Teff as are
Optical types
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At this time..
the latest T8 dwarfs
are believed to be about
Teff ~ 700-750 K
The synthetic spectra from
Burrows models shown here
suggest what cooler objects
discovered by deeper surveys
will look like
Kirkpatrick (2006 PPl V review)
suggests 3 possible qualitative
changes in the spectra that
might trigger
A new spectral type Y
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McDonald Observatory workshop
The J Band Bump
at early-mid T types:
CO > CH4 (and H2)
Absorption switches
from J to K band
More flux gets out at
J Band despite
Lower Teff
Open circles: apparently
Single stars
Filled circles inside a circle:
Resolved binaries
McDonald Observatory workshop
McDonald Observatory workshop