WD J2356−209

WD J2356−209 (also known as WD 2354−211)^[4] is a white dwarf star located 65 pc (212 ly) away from the Earth.^[5] It is a very faint white dwarf, with an apparent visual magnitude of 21.03.^[6] Its visible spectrum is dominated by a broad absorption feature^[2] that has been attributed to pressure-broadened sodium D lines.^[7] The presence of this sodium absorption feature and the detection of spectral lines from other heavy elements (calcium, iron and magnesium) indicate that the photosphere of WD J2356−209 has been polluted by a recent rocky debris accretion episode. A detailed analysis of the spectrum of WD J2356−209 shows that the accreted planetesimal was abnormally sodium-rich, containing up to ten times more sodium than calcium.^[3] With an effective temperature of 4040 K, WD J2356−209 was the coolest metal-polluted white dwarf observed at the time (and also the oldest, with a white dwarf cooling age of about 8 Gyr).^[3]

WD J2356−209

Observation data Epoch J2000.0 (ICRS)      Equinox J2000.0 (ICRS)
Constellation	Vela
Right ascension	23h 56m 45.576s[1]
Declination	−20° 54′ 45.01″[1]
Characteristics
Spectral type	DC[2] or DZ[3]
Astrometry
Distance	211.3 ± 8.2 ly (64.8 ± 2.5 pc)[3] ly
Details
Surface gravity (log g)	8.26±0.15[3] cgs
Temperature	4,310±190[3] K
Age	8.0±0.8[3] Gyr
Database references
SIMBAD	data

See also

• List of exoplanets and planetary debris around white dwarfs
• WD J2147–4035 is the coldest and oldest metal-polluted white dwarf (as of September 2024)^[8]
• WD 2317+1830 is another cold metal-polluted white dwarf