BPM 37093

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BPM 37093
Observation data
Epoch J2000.0 (ICRS)
Constellation
(pronunciation)		 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 km/s
Parallax (π) 61.0 ± 9.4[3] mas
Distance approx. 53 ly
(approx. 16 pc)
Details
Mass ? M☉
Radius 0.00145 R☉
Luminosity 0.0006 L☉
Temperature ? K
Metallicity ?
Rotation ?
Age ? years
Other designations
V886 Cen, V886 Centauri, GJ 2095, LFT 931, LHS 2594, LTT 4816, WD 1236-495
Database references
SIMBAD data

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.[5]

In the 1960s, it was predicted that as a white dwarf cools, its material should crystallize, starting at the center.[6] When a star pulsates, observing its pulsations gives information about its structure. BPM 37093 was first observed to be a pulsating variable in 1992[7], and in 1995 it was pointed out that this yielded a potential test of the crystallization theory.[8] 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.[6][9][10][4] Other work gives a crystallized mass fraction of between 32% and 82%.[11] Any of these estimates would result in a total crystalline mass in excess of 5×1029 kilograms.

Body-centered cubic lattice
Body-centered cubic lattice

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.[9]


[edit] References

  1. ^ a b c d BPM 37093, query result in SIMBAD. Accessed on line April 1, 2008.
  2. ^ a b 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.
  3. ^ 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.
  4. ^ a b 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., arXiv:astro-ph/0411199
  5. ^ Late stages of evolution for low-mass stars, Michael Richmond, lecture notes, Physics 230, Rochester Institute of Technology, accessed online May 3, 2007.
  6. ^ 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. Paper at ADSABS
  7. ^ 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. Paper at ADSABS
  8. ^ The Status of White Dwarf Asteroseismology and a Glimpse of the Road Ahead, D. E. Winget, Baltic Astronomy 4 (1995), pp. 129–136. Paper at ADSABS
  9. ^ a b BBC News: Diamond star thrills astronomers
  10. ^ Press release, 2004, Harvard-Smithsonian Center for Astrophysics.
  11. ^ P. Brassard, G. Fontaine, Asteroseismology of the Crystallized ZZ Ceti Star BPM 37093: A Different View, Astrophysical Journal 622, #1, pp. 572–576. Paper at ADSABS
  12. ^ 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. Paper at ADSABS