From Brown Dwarfs to Giant Planets
PHY 688Stanimir Metchev
Jan 26, 2009 PHY 688, Lecture 1 2
Course Focus• brown dwarfs and extrasolar planets
– structure– population– formation
• observational perspective– direct imaging and spectroscopy
• context:– low-mass stars– solar system planets
Jan 26, 2009 PHY 688, Lecture 1 3
Course Organization• weekly lectures
– MWF 10:40–11:35am• lecture notes
– after lectures, on course website• weekly readings
– “New Light on Dark Stars” (Reid & Hawley 2005, 2nd ed.)• bookstore ($???)• amazon.com: $95 new, from $70 used
– select scientific papers• NASA ADS (http://adsabs.harvard.edu/abstract_service.html)
• bi-weekly problem sets– from textbook + other sources
• office hours– MTh 1–2pm, ESS 452
Jan 26, 2009 PHY 688, Lecture 1 4
Evaluation of Coursework
• bi-weekly problem sets (40% of grade)– collaborative, but shown own work
• mid-term (30%)– closed book, formula sheet
• oral presentations (20%)– list of suggested topics from course website
• evaluations of peers’ oral presentations (10%)– i.e., “an evaluation of your evaluations”
Jan 26, 2009 PHY 688, Lecture 1 5
Course Material• overview of astronomical concepts• internal structure of low-mass stars, brown dwarfs, giant
planets• substellar atmospheres & evolution• detection and properties of brown dwarfs• detection and properties of extrasolar planets• star, planet, and brown dwarf formation
• can expand with suggestions– or present topic of interest at final oral presentation
Jan 26, 2009 PHY 688, Lecture 1 6
Prerequisite Knowledge
• required– classical mechanics– thermodynamics– E&M
• optional– fundamental astronomy– stellar structure– basic computer programming
Jan 26, 2009 PHY 688, Lecture 1 7
Perspective and History
Lecture 1
Jan 26, 2009 PHY 688, Lecture 1 8
Brown Dwarfs:Link between Stars and Giant Planets
• no H fusion• <0.07 M ~ 75 MJup
• star-like properties:– formation, self-
luminous, B fields,multiplicity
Burrows et al. (2001)
starsbrown dwarfs“planets”
Jan 26, 2009 PHY 688, Lecture 1 9
Brown Dwarfs:Link between Stars and Giant Planets
• no H fusion• <0.07 M ~ 75 MJup
• star-like properties:– formation, self-
luminous, B fields,multiplicity
Burrows et al. (2001)
starsbrown dwarfs“planets”
Jan 26, 2009 PHY 688, Lecture 1 10
Brown Dwarfs:Link between Stars and Giant Planets
Burrows et al. (2001)
starsbrown dwarfs“planets”
giant planet formationgiant planet formation
13 MJup10 M
Jup
5 MJup
1 MJup
starsbrown dwarfs“planets”M
• no H fusion• <0.07 M ~ 75 MJup
• star-like properties:– formation, self-
luminous, B fields,multiplicity
• planet-like properties:– low Teff, mass, clouds
and “weather”, radius
Jan 26, 2009 PHY 688, Lecture 1 11
The Stellar/Substellar Continuum
Sun
M dwarf T dwarfL dwarf Jupiter
brown dwarfs planetsstars
5700 K ~3500 K ~2000 K ~1000 K 160 K
(G dwarf)
R. Hurt (Caltech/IPAC)visible light
Jan 26, 2009 PHY 688, Lecture 1 12
Jan 26, 2009 PHY 688, Lecture 1 13
Significance of Brown Dwarfs
• important component of galactic population– as numerous as stars?
• unique probes of Galactic processes– star formation, metal enrichment, dynamics
• extreme low-temperature environments– chemistry, clouds, exo-solar climatology
• planetary analogues?– directly detectable
Jan 26, 2009 PHY 688, Lecture 1 14
Brown Dwarfs as Dark Matter?
NGC 720Chandra X-ray Observatory
Jan 26, 2009 PHY 688, Lecture 1 15
Extrapolation of IMF to Low Masses
• Salpeter (1955) IMF– dN*/dM ∝ M–2.35
• Extrapolation to0.01MSun– 8x more mass in
brown dwarfs thanstars!
!
" M( ) =dN
d log(M /MSun )
Jan 26, 2009 PHY 688, Lecture 1 16
BDs: a Theoretical Expectation
• Kumar (1963)– modeling of
<0.1MSun stars– importance of
electron degeneracy• minimum mass
below which objectscan not fuse H
Jan 26, 2009 PHY 688, Lecture 1 17
The Long Search for Brown Dwarfs
Jan 26, 2009 PHY 688, Lecture 1 18
1985: van Biesbroeck 8B• first claim of a detected brown dwarf
– McCarthy et al. (1985, ApJ)– vB 8A is an M7V member of the Hyades open cluster
• speckle interferometry– better than seeing limited (~1”) resolution– vB 8B: ~1” away, 3 mag fainter than primary in NIR– Kitt Peak 3.8 and 2.3m telescopes; two nights in 1984; H+K
near-IR bands• impetus for theoretical modeling of brown dwarfs
Jan 26, 2009 PHY 688, Lecture 1 19
1985: van Biesbroeck 8B• first claim of a detected brown dwarf
– McCarthy et al. (1985, ApJ)– vB 8A is an M7V member of the Hyades open cluster
• speckle interferometry– better than seeing limited (~1”) resolution– vB 8B: ~1” away, 3 mag fainter than primary in NIR– Kitt Peak 3.8 and 2.3m telescopes; two nights in 1984; H+K
near-IR bands• impetus for theoretical modeling of brown dwarfs
• never confirmed!
Jan 26, 2009 PHY 688, Lecture 1 20
1988: GD 165B
• Zuckerman & Becklin (1988, Nature)– GD 165A is a white dwarf
• direct imaging• bizarre spectrum
– BD or polluted star?
J H K
2MASS
Jan 26, 2009 PHY 688, Lecture 1 21
1989: HD 114762b
• Latham et al. (1989,Nature)
• precision radialvelocity
• M sin i = 11 MJup– a brown dwarf, a
planet, or a star?
Jan 26, 2009 PHY 688, Lecture 1 22
to be continued…