WD J1330+6435
White dwarf
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WD J1330+6435, also known as SDSS J1330+6435, is a white dwarf located 281.6 light-years (86.35 parsecs) from the Solar System in the constellation Draco, slightly northeast of Thuban and nearly directly south of Kappa Draconis. It appears green in colour due to strong absorption by sodium and calcium in its atmosphere.[5][7]
Visible spectrum of WD J1330+6435 (left) and its simulated surface colour (right) Credit: Mark A. Hollands et al. | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Draco |
| Right ascension | 13h 30m 00.89502s[1] |
| Declination | +64° 35′ 23.34744″[1] |
| Characteristics | |
| Spectral type | DZ[2] |
| Apparent magnitude (G) | 20.644728±0.009574[1] |
| Astrometry | |
| Proper motion (μ) | RA: −110.630±1.514 mas/yr[1] Dec.: −23.300±1.376 mas/yr[1] |
| Parallax (π) | 11.5812±0.7812 mas[1] |
| Distance | 280 ± 20 ly (86 ± 6 pc) |
| Details | |
| Mass | 0.74±0.10[3] M☉ |
| Surface gravity (log g) | 8.26±0.15[4] cgs |
| Temperature | 4310±190[4] K |
| Age | 9.1+1.1 −0.5[3] Gyr |
| Other designations | |
| WD J133001.17+643523.69[5], SDSS J133001.17+643523.69[6] | |
| Database references | |
| SIMBAD | data |
Nomenclature
The name WD J1330+6435, shortened from WD J133001.17+643523.69,[8][5] indicates that it is a white dwarf located at right ascension of 13h 30m and declination of +64° 35′. It is sometimes referred to by its Sloan Digital Sky Survey designation as SDSS J133001.17+643523.69[6] or SDSS J133001.13+643523.7,[9][10] both shortened to SDSS J1330+6435.
The star is listed on SIMBAD as WD 1328+648, from the McCook-Sion White Dwarf Catalog.[11] It indicates the star's position at epoch 1950.[12]
Properties
WD J1330+6435 is a white dwarf, radiating away its remaining heat and cooling over time rather than generating energy through nuclear fusion. This star's effective temperature is relatively low, at only around 4300 K.[9][5]
WD J1330+6435 has a spectral type of DZ, indicating that it is a white dwarf whose spectrum shows metal absorption lines.[2] It displays strong sodium, calcium, and lithium absorption lines.[13][6][9] Its atmosphere is nearly pure helium, with hydrogen making up less than 1 in 10000 of all atoms.[6] The star's cool, dense atmosphere results in extreme broadening of the metal absorption lines, allowing them to significantly alter the star's colour. Due to strong sodium absorption at orange wavelengths and calcium absorption at violet wavelengths, WD J1330+6435 appears green in colour.[5]
The presence of these elements in the star's atmosphere requires accretion of materials from the surrounding planetary system. The nature of the infalling material is not known with certainty, and could either be primitive planetesimals or pieces of differentiated bodies.[3]