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Gliese 229B
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Brown dwarf Gliese 229B is visible as a small dot next to its larger companion, the red dwarf Gliese 229A
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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.
| Host star | |
|---|---|
| Distance | 21.8 light-years (6.7 parsecs) |
| Spectral type | M1 V |
| Absolute magnitude | 8.14 |
| Brown dwarf | |
|---|---|
| Mass | 20-50 MJ |
| Semimajor axis | ~44 AU (6.6 billion km, 4.1 billion miles) |
| Orbital period | ~40 years |
| Year of discovery | 1995 |
| Discoverers | Caltech/Johns Hopkins team at Mt Palomar |
| Method of discovery | infrared imaging |
Related categories
• EXTRASOLAR PLANETS AND SUBSTELLAR OBJECTS
• NOTABLE STARS
References
- 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, 1678 (1996).
- Oppenheimer, B. R., Kulkarni, S. R., Matthews, K., and Nakajima, T. "Near IR Spectrum of the Cool Brown Dwarf GL229B," Science, 270, 1478 (1995).
- 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).
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