from brown dwarfs to giant planets · •weekly readings –“new light on ... –gd 165a is a...

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







Jan 26, 2009 PHY 688, Lecture 1 10




giant planet formationgiant planet formation

13 MJup10 M

Jup

5 MJup

1 MJup

starsbrown dwarfs“planets”M




• 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…

from brown dwarfs to giant planets · •weekly readings –“new light on ... –gd 165a is a...

Documents