PRESS RELEASEPRESS RELEASE WHO?WHO? Astronomers at UCLA and IPAC using the Keck Observatory. Astronomers at UCLA and IPAC using the Keck Observatory.

– Team members are Ian McLean (PI), Adam Burgasser, Davy Kirkpatrick (IPAC), Mark Team members are Ian McLean (PI), Adam Burgasser, Davy Kirkpatrick (IPAC), Mark McGovern, Lisa Prato and Sungsoo KimMcGovern, Lisa Prato and Sungsoo Kim

WHAT?WHAT? Announce the release of an ATLAS of Announce the release of an ATLAS of infrared spectral fingerprintsinfrared spectral fingerprints for for over 50 recently discovered Jupiter-sized objects called Brown Dwarfs.over 50 recently discovered Jupiter-sized objects called Brown Dwarfs.– Brown Dwarfs are objects about the size of Jupiter. They are composed mainly of Brown Dwarfs are objects about the size of Jupiter. They are composed mainly of

hydrogen gas, but because they have less than about 75 times the mass of Jupiter they hydrogen gas, but because they have less than about 75 times the mass of Jupiter they cannot sustain the nuclear reactions needed to shine like the Sun. As soon as they cannot sustain the nuclear reactions needed to shine like the Sun. As soon as they form, they fade in brightness. Only discovered within the last decade, the heat glow form, they fade in brightness. Only discovered within the last decade, the heat glow from these faint objects can be detected using infrared cameras.from these faint objects can be detected using infrared cameras.

– Brown Dwarfs are the “missing link” between stars and gas giant planets. By obtaining Brown Dwarfs are the “missing link” between stars and gas giant planets. By obtaining their infrared spectra astronomers can discover the physical and chemical properties of their infrared spectra astronomers can discover the physical and chemical properties of Brown Dwarfs and relate them to the giant planets of our Solar System.Brown Dwarfs and relate them to the giant planets of our Solar System.

WHERE?WHERE? The W.M. Keck Observatory, Mauna Kea, Hawaii operated by the The W.M. Keck Observatory, Mauna Kea, Hawaii operated by the California Association for Research in Astronomy (CARA). California Association for Research in Astronomy (CARA). – The twin telescopes of the Keck Observatory each have 10-m (400-in) diameter The twin telescopes of the Keck Observatory each have 10-m (400-in) diameter

segmented mirrors, the largest in the world.segmented mirrors, the largest in the world. WHEN?WHEN? Results will appear in the October 10 issue of the Results will appear in the October 10 issue of the Astrophysical JournalAstrophysical Journal

– (McLean et al. 2003)(McLean et al. 2003).. HOW?HOW? The atlas was produced after 4 years of careful data-gathering using The atlas was produced after 4 years of careful data-gathering using

NIRSPECNIRSPEC, a unique 1-ton vacuum-cryogenic spectrometer, designed and built at , a unique 1-ton vacuum-cryogenic spectrometer, designed and built at UCLA in collaboration with UCB. NIRSPEC contains powerful new infrared UCLA in collaboration with UCB. NIRSPEC contains powerful new infrared imaging devices developed by companies in California.imaging devices developed by companies in California.

NIRSPEC on the Right Nasmyth of Keck 2

NIRSPEC

The Near-Infrared Spectrometer at

the Keck Observatory

Infrared image of a star-forming region. Three infrared wavelengths are coded with the normal colors blue, green and red to make a picture of what our eyes might see if they were sensitive to infrared.

The reddest objects in this picture however, are completely invisible and much too red to see with our eyes.

Hot star

Cool star

Most of the energy emitted by very cool stars and Brown Dwarfs (failed stars) emerges in the INFRARED

INFRARED DETECTS COOLER OBJECTS

Image obtained with UCLA twin-channel infrared camera at Lick Observatory

The Sun

Jupiter

About same size as Jupiter, but with a mass from 13-75 times greater. Above 75 Jupiter masses the temperature inside the object becomes hot enough to sustain nuclear fusion and the object is a Red Dwarf star. Brown Dwarfs have no sustainable energy source and simply fade like a hot coal pulled from the fire.

Brown Dwarf

SEARCHING FOR OBJECTS LESS MASSIVE THAN SMALLEST RED DWARF STARS – Brown Dwarfs

The 2 MICRON ALL SKY SURVEY (2MASS)

Discovery of 2 new spectral classes of objects: L dwarfs and T dwarfs.

The Letters are used to indicate a distinctive spectral appearance.

Spectra are like fingerprints

A Spectral Atlas: atomic and molecular fingerprints

McLean et al. (2003): to appear in the Astrophysical Journal, Vol 596, October 10.

The W.M. Keck Observatory

M stars

L dwarfs

T dwarfs

The Optical Spectrum of the Sun

Dark lines indicate “missing light” absorbed by the hot, thin hydrogen gas at the Sun’s outer edge

The Infrared Spectrum of an L dwarfAs our eyes might see it if they were infrared sensitive

Dark bands are due to super-heated steam (H2O) forming high in the cool atmosphere of the L dwarf

The Infrared Spectrum of a T dwarfAs our eyes might see it if they were infrared sensitive

Large dark regions are due to absorption by H2O and methane (CH4) – similar to the spectrum of Jupiter

Optical Region~ same scale

UV IR

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.95 1.15 1.35 1.55 1.75 1.95 2.15

Wolf 359 (M6) Gl570D T(8)

INFRARED SPECTRA of a RED DWARF star compared with that of a very cool sub-stellar

BROWN DWARF

Wolf 359 (red dwarf star)

Gl570D (sub-stellar object or Brown Dwarf)

The dramatic difference in appearance is due to absorption by METHANE (CH4) in the atmosphere of the Jupiter-sized Brown Dwarf

Inte

nsity

Wavelength (microns)

Better resolution than in previous infrared spectraBetter resolution than in previous infrared spectra Higher quality spectra, revealing more subtle relationshipsHigher quality spectra, revealing more subtle relationships

– A fundamental data base for theoretical modelsA fundamental data base for theoretical models J-band spectra of 53 objects covering temperature range J-band spectra of 53 objects covering temperature range

from about 2500 K to about 750 K (M, L and T types) from about 2500 K to about 750 K (M, L and T types) 25 objects with complete flux-calibrated near-infrared 25 objects with complete flux-calibrated near-infrared

spectra, 12 of these have overlap region with optical spectra, 12 of these have overlap region with optical spectraspectra

Results:Results:– Combination of 4 bands due to H2O, and 2 bands due to CH4 can Combination of 4 bands due to H2O, and 2 bands due to CH4 can

be used for identifying the type of Brown Dwarf and assigning an be used for identifying the type of Brown Dwarf and assigning an approximate Temperatureapproximate Temperature

– Strong absorption lines due to the alkali element potassium are Strong absorption lines due to the alkali element potassium are sensitive to pressure in the Brown Dwarf atmosphere, which is sensitive to pressure in the Brown Dwarf atmosphere, which is controlled by the Mass of the object through gravitycontrolled by the Mass of the object through gravity

– Spectral shapes are influenced by formation of cloud layersSpectral shapes are influenced by formation of cloud layers

RESULTS & HIGHLIGHTS