BPM 37093

Starbox observe|epoch=J2000.0 (ICRS)
constell=Centaurus
ra=RA|12|38|49.93SIMBAD link|BPM+37093|BPM 37093, query result in SIMBAD. Accessed on line April 1, 2008.]
dec=DEC|-49|48|01.2
appmag_v=14.0Starbox character
class=DAV4.4 [http://adsabs.harvard.edu/abs/1999ApJS..121....1M 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 [http://vizier.u-strasbg.fr/viz-bin/Cat?III/210 III/210] .]
variable=DAV (ZZ Ceti) Starbox astrometry
radial_v=−12
parallax=61.0
p_error=9.4
parallax_footnote=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] Starbox detail
mass=1.10
radius=
luminosity=0.001
temperature=11730 ± 350
metal=
gravity=8.81 ± 0.05
rotation=
age= Starbox catalog|names=V886 Cen, V886 Centauri, GJ 2095, LFT 931, LHS 2594, LTT 4816, WD 1236-495

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. 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. [http://spiff.rit.edu/classes/phys230/lectures/planneb/planneb.html Late stages of evolution for low-mass stars] , Michael Richmond, lecture notes, Physics 230, Rochester Institute of Technology, accessed online May 3, 2007.]

In the 1960s, it was predicted that as a white dwarf cools, its material should crystallize, starting at the center.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] When a star pulsates, observing its pulsations gives information about its structure. BPM 37093 was first observed to be a pulsating variable in 1992 [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] , and in 1995 it was pointed out that this yielded a potential test of the crystallization theory. [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] 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. [http://news.bbc.co.uk/2/hi/science/nature/3492919.stm BBC News: Diamond star thrills astronomers] ] [ [http://cfa-www.harvard.edu/press/pr0407.html Press release] , 2004, Harvard-Smithsonian Center for Astrophysics.] 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.] Other work gives a crystallized mass fraction of between 32% and 82%.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] Any of these estimates would result in a total crystalline mass in excess of 5e|29 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. [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] 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".

References

External links

* [http://jumk.de/astronomie/special-stars/bpm-37093.shtml BPM 37093 (Diamond Star)]
* [http://thexodirectory.com/2007/12/astronomers-discovered-largest-diamond.html]