The first confirmed brown dwarf. It is
in orbit around the nearby red dwarf, Gliese
229, in the constellation of Lepus.
| Brown dwarf Gliese 229B is visible as a small dot
next to its larger companion, the red dwarf Gliese 229A
Gliese 229B was discovered in 1994 by a team of astronomers from Caltech
and Johns Hopkins University using the 60-inch. reflector at Palomar
Observatory equipped with an adaptive
optics coronograph, an image-sharpening
device developed at Johns Hopkins. Further imaging was performed using the
Hubble Space Telescope and an infrared
spectrum was obtained using the Palomar 200-inch. This spectrum showed strong
absorption lines due to methane,
strikingly similar to those found in the spectrum of Jupiter's
atmosphere. Since methane can only exist at temperatures less than 1,200
K and the coolest stars have a surface temperature of 1,800 K, this is conclusive
evidence that Gliese 229B is not a star. There remains, however, a possibility
that it may be a very massive planet. The decisive factor is how GL 229B
formed. If it condensed like a star from an interstellar
cloud then it is certainly a brown dwarf. On the other hand, if it grew
by accretion in a circumstellar
disk, then some astronomers would argue that it is a large planet. If
the former is the case, then it is likely to have a much more elongated
orbit (like that of most binary stars) than if it were planetary in nature.
This determination may take a number of years, however, since GL 229B is
in a wide orbit around its primary, similar in size to the orbit of Pluto
around the Sun.
||21.8 light-years (6.7 parsecs)
||~44 AU (6.6 billion km, 4.1 billion miles)
|year of discovery
||Caltech/Johns Hopkins team at Mt Palomar
|method of discovery
- Allard, F., Hauschildt, P. H., Baraffe, I., and Chabrier, G. "Synthetic
Spectra and Mass Determination of the Brown Dwarf GL229B," Astrophysical
Journal Letters, 465, L123 (1996).
- Griffith, C., Yelle, R., and Marley, M. "The Dusty Atmosphere of the
Brwon Dwarf Gliese 229B," Science, 282, 2063 (1998).
- Matthews, K., Nakajima, T., Kulkarni, S. R., and Oppenheimer, B. R.
"Spectral Energy Distribution and Bolometric Luminosity of the Cool
Brown Dwarf Gliese 229B," Astrophysical Journal, 112,
- Oppenheimer, B. R., Kulkarni, S. R., Matthews, K., and Nakajima, T.
"Near IR Spectrum of the Cool Brown Dwarf GL229B," Science, 270,
- Oppenheimer, B. R., Kulkarni, S. R., Matthews, K., and Van Kerrwijk,
M. H. "The Spectrum of of the Cool Brown Dwarf Gliese 229B," Astrophysical
Journal, 502, 932 (1998).
PLANETS AND SUBSTELLAR OBJECTS