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WD J1330+6435

From Quire, the open reference·White dwarf star in the constellation Draco·2 min read
WD J1330+6435
WD J1330+6435
Image: source and license
Observation data
Epoch J2000      Equinox ICRS
ConstellationDraco[1]
Right ascension13h 30m 01.16366s[2]
Declination+64° 35′ 23.7116″[2]
Characteristics
Spectral typeDZ[3]
Apparent magnitude (G)20.645±0.010[2]
Astrometry
Proper motion (μ) · RA: −110.630±1.514 mas/yr[2]
Dec.: −23.300±1.376 mas/yr[2]
Parallax (π) · 11.5812±0.7812 mas[2]
Distance · 280 ± 20 ly
(86 ± 6 pc)
Details
Mass · 0.74±0.10[4] M☉
Surface gravity (log g) · 8.26±0.15[5] cgs
Temperature · 4310±190[5] K
Age · 9.1+1.1
−0.5[4] Gyr
Other designations
WD J133001.17+643523.69[6], SDSS J133001.17+643523.69[7]
Database references
SIMBAD · data

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,[6][8] making it a rare example of a green star. It is the first star found with this hue.[9]

Nomenclature#edit

The name WD J1330+6435, shortened from WD J133001.17+643523.69,[10][6] indicates that it is a white dwarf located at a right ascension of 13h 30m and a declination of +64° 35′. It is sometimes referred to by its Sloan Digital Sky Survey designation as SDSS J133001.17+643523.69[7] or SDSS J133001.13+643523.7,[11][12] both shortened to SDSS J1330+6435.

The star was first documented in 1999 in the McCook-Sion White Dwarf Catalog where it is listed as WD 1328+648, indicating the star's position at epoch B1950.0.[13][14]

Properties#edit

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.[11][6] Its atmosphere is nearly pure helium, with hydrogen making up less than 1 in 10000 of all atoms.[7]

WD J1330+6435 has a spectral type of DZ, indicating that it is a white dwarf whose spectrum shows metal absorption lines.[3] It displays strong sodium, calcium, and lithium absorption lines.[15][7][11] The star's cool, dense atmosphere results in extreme broadening of these 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.[6]

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.[4]

According to Mark Hollands of the England's University of Warwick and lead author of a 2026 study that concluded its greenish tone, the star's density is so high that the sodium atoms are continually being bombarded by neighboring helium atoms, changing the sodium atomic energy levels. "The end result is that the sodium atoms no longer absorb one very narrow wavelength of orange—they absorb the yellows, oranges and some of the red ​wavelengths. And what you're left with is a star that has a beautiful chartreuse green glow, something that wouldn't be possible for sun-like stars," Hollands said.[16]

References#edit

  1. ^ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
  2. ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b Gentile Fusillo, N P; Tremblay, P-E; Cukanovaite, E; et al. (22 October 2021). "A catalogue of white dwarfs in Gaia EDR3". Monthly Notices of the Royal Astronomical Society. 508 (3): 3877–3896. arXiv:2106.07669. Bibcode:2021MNRAS.508.3877G. doi:10.1093/mnras/stab2672. ISSN 0035-8711. Retrieved 16 October 2026.
  4. ^ a b c Kaiser, Benjamin C.; Clemens, J. Christopher; Blouin, Simon; et al. (1 February 2025). "The Origins of Lithium Enhancement in Polluted White Dwarfs". The Astrophysical Journal. 979 (2): 111. arXiv:2412.01878. Bibcode:2025ApJ...979..111K. doi:10.3847/1538-4357/ad9a6d. ISSN 0004-637X.
  5. ^ a b Blouin, S.; Dufour, P.; Allard, N. F.; et al. (20 February 2019). "A New Generation of Cool White Dwarf Atmosphere Models. III. WD J2356–209: Accretion of a Planetesimal with an Unusual Composition". The Astrophysical Journal. 872 (2): 188. arXiv:1902.03219. Bibcode:2019ApJ...872..188B. doi:10.3847/1538-4357/ab0081. ISSN 0004-637X.
  6. ^ a b c d e Hollands, Mark A; Gänsicke, Boris T; Tremblay, Pier-Emmanuel; et al. (6 January 2026). "Any colour you like: the diverse chromaticities of white dwarfs". RAS Techniques and Instruments. 5 rzag069. arXiv:2610.18966. doi:10.1093/rasti/rzag069. ISSN 2752-8200.
  7. ^ a b c d Hollands, Mark A.; Tremblay, Pier-Emmanuel; Gänsicke, Boris T.; et al. (11 February 2021). "Alkali metals in white dwarf atmospheres as tracers of ancient planetary crusts". Nature Astronomy. 5 (5): 451–459. arXiv:2101.01225. Bibcode:2021NatAs...5..451H. doi:10.1038/s41550-020-01296-7. ISSN 2397-3366. Retrieved 16 October 2026.
  8. ^ Higgs, Matt. "Astronomers reveal surprising true colours of white dwarfs". University of Warwick. Retrieved 16 October 2026.
  9. ^ iain.todd@ourmedia.co.uk (16 October 2026). "They've done it. Scientists have found a green star. Here's the science behind the new discovery and the technicolour cosmos". BBC Sky at Night Magazine. Retrieved 17 October 2026.
  10. ^ Elms, Abbigail K; Tremblay, Pier-Emmanuel; Gänsicke, Boris T; et al. (5 November 2022). "Spectral analysis of ultra-cool white dwarfs polluted by planetary debris". Monthly Notices of the Royal Astronomical Society. 517 (3): 4557–4574. arXiv:2206.05258. Bibcode:2022MNRAS.517.4557E. doi:10.1093/mnras/stac2908. ISSN 0035-8711. Retrieved 16 October 2026.
  11. ^ a b c Kaiser, B. C.; Clemens, J. C.; Blouin, S.; et al. (8 January 2021). "Lithium pollution of a white dwarf records the accretion of an extrasolar planetesimal". Science. 371 (6525): 168–172. arXiv:2012.12900. Bibcode:2021Sci...371..168K. doi:10.1126/science.abd1714. ISSN 0036-8075. PMID 33335019. Retrieved 17 October 2026.
  12. ^ "SDSS J133001.13+643523.7 -- White Dwarf". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 17 October 2026.
  13. ^ McCook, George P.; Sion, Edward M. (1999). "A Catalog of Spectroscopically Identified White Dwarfs". The Astrophysical Journal Supplement Series. 121 (1): 1–130. Bibcode:1999ApJS..121....1M. doi:10.1086/313186. ISSN 0067-0049. Retrieved 17 October 2026.
  14. ^ "McCook-Sion White Dwarf Catalog (Web Version)". HEASARC. 25 April 2014. Retrieved 17 October 2026.
  15. ^ Harris, Hugh C.; Liebert, James; Kleinman, S. J.; et al. (2003). "An Initial Survey of White Dwarfs in the Sloan Digital Sky Survey". The Astronomical Journal. 126 (2): 1023–1040. arXiv:astro-ph/0305347. Bibcode:2003AJ....126.1023H. doi:10.1086/376842. ISSN 0004-6256. Retrieved 17 October 2026.
  16. ^ Dunham, Will (16 October 2026). "Newly identified green star leaves astronomers amazed". Reuters.


Categories Draco (constellation)DZ white dwarfs

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