BPM 37093
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 12h 38m 49.93s[1] |
| Declination | −49° 48′ 01.2″[1] |
| Apparent magnitude (V) | 14.0[1] |
| Characteristics | |
| Spectral type | DAV4.4[2] |
| Variable type | DAV (ZZ Ceti)[2] |
| Astrometry | |
| Radial velocity (Rv) | −12[2] km/s |
| Parallax (π) | 61.0 ± 9.4 mas[3] |
| Distance | approx. 53 ly (approx. 16 pc) |
| Details | |
| Mass | 1.10[4] M☉ |
| Luminosity | 0.001[3] L☉ |
| Surface gravity (log g) | 8.81 ± 0.05[5] cgs |
| Temperature | 11730 ± 350[5] K |
| Other designations | |
V886 Cen, V886 Centauri, GJ 2095, LFT 931, LHS 2594, LTT 4816, WD 1236-495[1] | |
BPM 37093 is a variable white dwarf star of the DAV, or ZZ Ceti, type, with a hydrogen atmosphere and an unusually high mass of approximately 1.1 times the Sun's. It is about 50 light-years from Earth, in the constellation Centaurus, and vibrates; these pulsations cause its luminosity to vary.[4][1] Like other white dwarfs, BPM 37093 is thought to be composed primarily of carbon and oxygen, which are created by thermonuclear fusion of helium nuclei in the triple-alpha process.[6]
Since the "star" may be composed entirely of crystallized carbon it would be a diamond with roughly the same mass as our sun. In diamond terms, it is a weight of 10 billion, trillion carats.
In the 1960s, it was predicted that as a white dwarf cools, its material should crystallize, starting at the center.[7] When a star pulsates, observing its pulsations gives information about its structure. BPM 37093 was first observed to be a pulsating variable in 1992[8], and in 1995 it was pointed out that this yielded a potential test of the crystallization theory.[9] In 2004, Travis Metcalfe and a team of researchers at the Harvard-Smithsonian Center for Astrophysics estimated, on the basis of these asteroseismological observations, that approximately 90% of the mass of BPM 37093 had crystallized.[7][10][11][4] Other work gives a crystallized mass fraction of between 32% and 82%.[5] Any of these estimates would result in a total crystalline mass in excess of 5×1029 kilograms.
Crystallization of the material of a white dwarf of this type is thought to result in a body-centered cubic lattice of carbon and/or oxygen nuclei, which are surrounded by a Fermi sea of electrons.[12] Since a diamond also consists of crystallized carbon, the star BPM 37093 has been nicknamed Lucy after The Beatles's hit Lucy in the Sky with Diamonds.[10]
References
- ^ a b c d e BPM 37093, query result in SIMBAD. Accessed on line April 1, 2008.
- ^ a b c A Catalog of Spectroscopically Identified White Dwarfs, George P. McCook and Edward M. Sion, Astrophysical Journal Supplement 121, #1 (March 1999), pp. 1–130. CDS ID III/210.
- ^ a b Photometric and Spectroscopic Analysis of Cool White Dwarfs with Trigonometric Parallax Measurements, P. Bergeron, S. K. Leggett, María Teresa Ruiz, Astrophysical Journal Supplement 133, #2 (April 2001), pp. 413–449. Bibcode:2001ApJS..133..413B
- ^ a b c Whole Earth Telescope observations of BPM 37093: a seismological test of crystallization theory in white dwarfs, A. Kanaan, A. Nitta, D. E. Winget, S. O. Kepler, M. H. Montgomery, T. S. Metcalfe, et al., Astronomy and Astrophysics 432, #1 (March 2005), pp. 219–224. Bibcode:2005A&A...432..219K doi:10.1051/0004-6361:20041125.
- ^ a b c P. Brassard, G. Fontaine, Asteroseismology of the Crystallized ZZ Ceti Star BPM 37093: A Different View, Astrophysical Journal 622, #1, pp. 572–576. Bibcode:2005ApJ...622..572B
- ^ Late stages of evolution for low-mass stars, Michael Richmond, lecture notes, Physics 230, Rochester Institute of Technology, accessed online May 3, 2007.
- ^ a b Testing White Dwarf Crystallization Theory with Asteroseismology of the Massive Pulsating DA Star BPM 37093, T. S. Metcalfe, M. H. Montgomery, and A. Kanaan, Astrophysical Journal 605, #2 (April 2004), pp. L133–L136. Bibcode:2004ApJ...605L.133M
- ^ The discovery of a new DAV star using IUE temperature determination, A. Kanaan, S. O. Kepler, O. Giovannini, and M. Diaz, Astrophysical Journal Letters 390, #2 (May 10, 1992), pp. L89–L91. Bibcode:1992ApJ...390L..89K
- ^ The Status of White Dwarf Asteroseismology and a Glimpse of the Road Ahead, D. E. Winget, Baltic Astronomy 4 (1995), pp. 129–136. Bibcode:1995BaltA...4..129W
- ^ a b BBC News: Diamond star thrills astronomers
- ^ Press release, 2004, Harvard-Smithsonian Center for Astrophysics.
- ^ Crystallization of carbon-oxygen mixtures in white dwarfs, J. L. Barrat, J. P. Hansen, and R. Mochkovitch, Astronomy and Astrophysics 199, #1–2 (June 1988), pp. L15–L18. Bibcode:1988A&A...199L..15B
External links
- BPM 37093 (Diamond Star)
- Largest diamond in galaxy predicts future of solar system, Pravda.ru, December 26, 2007.