BPM 37093 (V886 Centauri) 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 48 light-years (15 parsecs) from Earth in the constellation Centaurus and vibrates; these pulsations cause its luminosity to vary.[3][5] 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.[8]
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Centaurus |
Right ascension | 12h 38m 49.78112s[2] |
Declination | −49° 48′ 00.2195″[2] |
Apparent magnitude (V) | 14.0[3] |
Characteristics | |
Spectral type | DAV4.4[4] |
Variable type | DAV (ZZ Ceti)[4] |
Astrometry | |
Radial velocity (Rv) | −12[4] km/s |
Proper motion (μ) | RA: -557.111 mas/yr[2] Dec.: -74.036 mas/yr[2] |
Parallax (π) | 67.4058 ± 0.0186 mas[2] |
Distance | 48.39 ± 0.01 ly (14.836 ± 0.004 pc) |
Details | |
Mass | 1.10[5] M☉ |
Radius | 0.0057 R☉ |
Luminosity | 0.001[6] L☉ |
Surface gravity (log g) | 8.81 ± 0.05[7] cgs |
Temperature | 11730 ± 350[7] K |
Other designations | |
Database references | |
SIMBAD | data |
ARICNS | data |
In the 1960s, it was predicted that as a white dwarf cools, its material should crystallize, starting at the center.[9] When a star pulsates, observing its pulsations gives information about its structure. BPM 37093 was first observed to be a pulsating variable in 1992,[1] and in 1995 it was pointed out that this yielded a potential test of the crystallization theory.[10] In 2004, Antonio Kanaan and a team of researchers of the Whole Earth Telescope estimated, on the basis of these asteroseismological observations, that approximately 90% of the mass of BPM 37093 had crystallized.[5][9][11][12] Other work gives a crystallized mass fraction of between 32% and 82%.[7] Any of these estimates would result in a total crystalline mass in excess of 5×1029 kilograms. As the white dwarf has a radius of 4,000 kilometres (2,500 mi), this means that the core of BPM 37093, nicknamed Lucy, is likely one of the largest diamonds in the local region of the universe.[13][14]
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.[15]