# ESO 439-26

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White dwarf star

ESO 439-26 Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Hydra Right ascension 11h 39m 03.1037s[1] Declination −28° 52′ 16.628″[1] Apparent magnitude (V) 20.52[2] Characteristics Spectral type DC9[2] U−B color index 1.03[3] B−V color index 0.64[3] R−I color index 1.14[3] Astrometry Proper motion (μ) RA: -397.767 ±0.481[4] mas/yr Dec.: + 36.869 ±0.441[4] mas/yr Parallax (π) 9.7390±0.5007 mas[4] Distance 330 ± 20 ly (103 ± 5 pc) Absolute magnitude (MV) 15.46[2][4] Details Mass 0.50 ±0.15[5] M☉ Radius 0.0126[6] R☉ Luminosity 1.15 ×10−5 [3] L☉ Surface gravity (log g) 7.87 ±0.28[5] cgs Temperature 4,673±275[5] K Other designations Ruiz 439-26, WD 1136-286[1] Database references SIMBAD data

**ESO 439-26** is a [white dwarf](/source/White_dwarf) star. It was considered the least luminous white dwarf known.[2][7] Located 140 light years away from the [Sun](/source/Sun), it is roughly 10 billion years old and has a temperature of 4560 Kelvin (cooler than the Sun, at 5772 Kelvin). Thus, despite being classified as a "white dwarf", it would actually appear yellowish in color.[8]

This finding is however based on a too large [parallax](/source/Parallax). [Gaia](/source/Gaia_(spacecraft)) measurement of the parallax shows a more distant source and therefore an [absolute magnitude](/source/Absolute_magnitude) of MG=15.0 mag. For example the white dwarf [WD J2147–4035](/source/WD_J2147%E2%80%934035) has MG=17.7 mag, making this white dwarf less luminous.[9][5] The updated MV is 15.46, using the Gaia parallax[4] and the apparent V-magnitude from Ruiz et al. (see formulae at the article [absolute magnitude](/source/Absolute_magnitude#Apparent_magnitude)).[2]

## References

1. ^ [***a***](#cite_ref-s_1-0) [***b***](#cite_ref-s_1-1) [***c***](#cite_ref-s_1-2) ["Ruiz 439-26"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Ruiz+439-26). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved October 22, 2020.

1. ^ [***a***](#cite_ref-ruiz95_2-0) [***b***](#cite_ref-ruiz95_2-1) [***c***](#cite_ref-ruiz95_2-2) [***d***](#cite_ref-ruiz95_2-3) [***e***](#cite_ref-ruiz95_2-4) María Teresa Ruiz; P. Bergeron; S. K. Leggett; Claudio Anguita (1995). ["The Extremely Low Luminosity White Dwarf ESO 439-26"](https://iopscience.iop.org/article/10.1086/309845/fulltext/5601.text.html). *The Astrophysical Journal*. **455**. [Bibcode](/source/Bibcode_(identifier)):[1995ApJ...455L.159R](https://ui.adsabs.harvard.edu/abs/1995ApJ...455L.159R). [doi](/source/Doi_(identifier)):[10.1086/309845](https://doi.org/10.1086%2F309845). [S2CID](/source/S2CID_(identifier)) [120193018](https://api.semanticscholar.org/CorpusID:120193018).

1. ^ [***a***](#cite_ref-blr01_3-0) [***b***](#cite_ref-blr01_3-1) [***c***](#cite_ref-blr01_3-2) [***d***](#cite_ref-blr01_3-3) Bergeron, P.; Leggett, S. K.; Ruiz, María Teresa (April 2001). ["Photometric and Spectroscopic Analysis of Cool White Dwarfs with Trigonometric Parallax Measurements"](https://doi.org/10.1086%2F320356). *Astrophysical Journal Supplement Series*. **133** (2): 413–449. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0011286](https://arxiv.org/abs/astro-ph/0011286). [Bibcode](/source/Bibcode_(identifier)):[2001ApJS..133..413B](https://ui.adsabs.harvard.edu/abs/2001ApJS..133..413B). [doi](/source/Doi_(identifier)):[10.1086/320356](https://doi.org/10.1086%2F320356). [S2CID](/source/S2CID_(identifier)) [15511301](https://api.semanticscholar.org/CorpusID:15511301).

1. ^ [***a***](#cite_ref-Gaia_DR3_4-0) [***b***](#cite_ref-Gaia_DR3_4-1) [***c***](#cite_ref-Gaia_DR3_4-2) [***d***](#cite_ref-Gaia_DR3_4-3) [***e***](#cite_ref-Gaia_DR3_4-4) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D3483746453090944896%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Gaia_EDR3wd_5-0) [***b***](#cite_ref-Gaia_EDR3wd_5-1) [***c***](#cite_ref-Gaia_EDR3wd_5-2) [***d***](#cite_ref-Gaia_EDR3wd_5-3) Gentile Fusillo, N. P.; Tremblay, P. -E.; Cukanovaite, E.; Vorontseva, A.; Lallement, R.; Hollands, M.; Gänsicke, B. T.; Burdge, K. B.; McCleery, J.; Jordan, S. (2021-12-01). ["A catalogue of white dwarfs in Gaia EDR3"](https://doi.org/10.1093%2Fmnras%2Fstab2672). *Monthly Notices of the Royal Astronomical Society*. **508** (3): 3877–3896. [arXiv](/source/ArXiv_(identifier)):[2106.07669](https://arxiv.org/abs/2106.07669). [Bibcode](/source/Bibcode_(identifier)):[2021MNRAS.508.3877G](https://ui.adsabs.harvard.edu/abs/2021MNRAS.508.3877G). [doi](/source/Doi_(identifier)):[10.1093/mnras/stab2672](https://doi.org/10.1093%2Fmnras%2Fstab2672). [ISSN](/source/ISSN_(identifier)) [0035-8711](https://search.worldcat.org/issn/0035-8711).

1. **[^](#cite_ref-6)** Ruiz, Maria Teresa; Bergeron, P.; Leggett, S. K.; Anguita, Claudio (1995-12-01). ["The Extremely Low Luminosity White Dwarf ESO 439-26"](https://ui.adsabs.harvard.edu/abs/1995ApJ...455L.159R). *The Astrophysical Journal*. **455**: L159. [doi](/source/Doi_(identifier)):[10.1086/309845](https://doi.org/10.1086%2F309845). [ISSN](/source/ISSN_(identifier)) [0004-637X](https://search.worldcat.org/issn/0004-637X).

1. **[^](#cite_ref-noaoWeb_7-0)** ["The Faintest Known White Dwarf"](https://web.archive.org/web/20210312011057/https://www.noao.edu/noao/noaonews/mar96/art3.html). *www.noao.edu*. 1 March 1996. Archived from [the original](https://www.noao.edu/noao/noaonews/mar96/art3.html) on 12 March 2021. Retrieved 8 May 2020.

1. **[^](#cite_ref-bookKaler_8-0)** Kaler, James B. (May 7, 2006). [*The Hundred Greatest Stars*](https://books.google.com/books?id=jmoQBwAAQBAJ&q=ESO+439-26&pg=PA75). Springer Science & Business Media. [ISBN](/source/ISBN_(identifier)) [9780387216256](https://en.wikipedia.org/wiki/Special:BookSources/9780387216256) – via Google Books.

1. **[^](#cite_ref-Elms2022_9-0)** Elms, Abbigail K.; Tremblay, Pier-Emmanuel; Gänsicke, Boris T.; Koester, Detlev; Hollands, Mark A.; Gentile Fusillo, Nicola Pietro; Cunningham, Tim; Apps, Kevin (2022-12-01). ["Spectral analysis of ultra-cool white dwarfs polluted by planetary debris"](https://doi.org/10.1093%2Fmnras%2Fstac2908). *Monthly Notices of the Royal Astronomical Society*. **517** (3): 4557–4574. [arXiv](/source/ArXiv_(identifier)):[2206.05258](https://arxiv.org/abs/2206.05258). [Bibcode](/source/Bibcode_(identifier)):[2022MNRAS.517.4557E](https://ui.adsabs.harvard.edu/abs/2022MNRAS.517.4557E). [doi](/source/Doi_(identifier)):[10.1093/mnras/stac2908](https://doi.org/10.1093%2Fmnras%2Fstac2908). [ISSN](/source/ISSN_(identifier)) [0035-8711](https://search.worldcat.org/issn/0035-8711).

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