40 Eridani

Jump to navigation Jump to search

Template:Other stars by Bayer designation

40 Eridani
Diagram showing star positions and boundaries of the Eridanus constellation and its surroundings
Diagram showing star positions and boundaries of the Eridanus constellation and its surroundings
A star chart of the Eridanus constellation showing the position of 40 Eridani (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Eridanus
40 Eridani A
Right ascension  04h 15m 16.31963s[1]
Declination −07° 39′ 10.3404″[1]
Apparent magnitude (V) 4.43[1]
40 Eridani B
Right ascension  04h 15m 21.786s[2]
Declination −07° 39′ 29.22″[2]
Apparent magnitude (V) 9.52[3]
40 Eridani C
Right ascension  04h 15m 21.50s[4]
Declination −07° 39′ 22.3″[4]
Apparent magnitude (V) 11.17[3]
Characteristics
40 Eridani A
Spectral type K0.5V[5]
U−B color index +0.45[3]
B−V color index +0.82[1]
40 Eridani B
Spectral type DA4[3]
U−B color index +0.45[3]
B−V color index +0.03[3]
40 Eridani C
Spectral type M4.5eV[6]
U−B color index +0.83[3]
B−V color index +1.67[3]
Variable type Flare star[7]
Astrometry
40 Eridani A
Radial velocity (Rv)−43.0[8] km/s
Proper motion (μ) RA: −2,240.12[1] mas/yr
Dec.: −3,420.27[1] mas/yr
Parallax (π)200.62 ± 0.23[1] mas
Distance16.26 ± 0.02 ly
(4.985 ± 0.006 pc)
Absolute magnitude (MV)5.93[9]
40 Eridani B
Radial velocity (Rv)−21[10] km/s
Proper motion (μ) RA: −2,228.3[2] mas/yr
Dec.: −3,377.1[2] mas/yr
40 Eridani C
Radial velocity (Rv)−46[3] km/s
Proper motion (μ) RA: −2,250[11] mas/yr
Dec.: −3,408[11] mas/yr
Parallax (π)199.4552 ± 0.3204[11] mas
Distance16.35 ± 0.03 ly
(5.014 ± 0.008 pc)
Orbit
Primary40 Eridani A
Companion40 Eridani BC
Period (P)~8,000[12] yr
Semi-major axis (a)~400[13] AU
Orbit[14]
Primary40 Eridani B
Companion40 Eridani C
Period (P)230.30±0.68 yr
Semi-major axis (a)6.930±0.050"
(~35 AU)
Eccentricity (e)0.4294±0.0027
Inclination (i)107.56±0.29°
Longitude of the node (Ω)151.44±0.12°
Periastron epoch (T)1847.7±1.1
Argument of periastron (ω)
(secondary)		318.4±1.1°
Details
40 Eridani A
Mass0.84 [8] M☉
Radius0.81[15] R☉
Luminosity0.457±0.002[16] L☉
Temperature5,300[8] K
Metallicity [Fe/H]−0.19[17] dex
Rotation~37–43[18] days
Rotational velocity (v sin i)1.23 ± 0.28[18] km/s
Age5.6[19] Gyr
40 Eridani B
Mass0.573±0.018[14] M☉
Radius0.014[20] R☉
Luminosity0.013[21] L☉
Temperature16,500[22] K
Age∼1.8 (cooling age ∼0.122)[23] Gyr
40 Eridani C
Mass0.2036±0.0064[14] M☉
Radius0.31[15] R☉
Luminosity0.008[note 1] L☉
Temperature3,100[24] K
Other designations
ο² Eri, 40 Eri, ADS 3093, CCDM J04153-0739, GCTP 945, Gliese 166
A: Keid,[25] HD 26965, HIP 19849, HR 1325, LHS 23, LTT 1907, SAO 131063, BD-07° 780
B: BD-07° 781, G 160-060, HD 26976, LHS 24, LTT 1908, SAO 131065
C: DY Eri, BD-07°781 C, LHS 25, LTT 1909
Database references
SIMBADThe system
A
B
C

40 Eridani (abbreviated 40 Eri), also designated Omicron² Eridani (ο² Eridani, abbreviated Omicron² Eri, ο² Eri), is a triple star system in the constellation of Eridanus. Based on parallax measurements taken during the Hipparcos mission, it is less than 17 light-years from the Sun.

The primary star of the system, designated 40 Eridani A, formally named Keid /ˈkaɪd/ from the traditional name for the system,[26][25] is easily visible to the naked eye. It is orbited by a binary pair whose two components are designated 40 Eridani B and C, and which were discovered on January 31, 1783, by William Herschel.[27]:p73 It was again observed by Friedrich Struve in 1825 and by Otto Struve in 1851.[12][28]

In 1910, it was discovered that although component B was a faint star, it was white in color. This meant that it had to be a small star; in fact it was a white dwarf, the first discovered.[29] Although it is neither the closest white dwarf, nor the brightest in the night sky, it is by far the easiest to observe; it is nearly three magnitudes brighter than Van Maanen's Star (the nearest solitary white dwarf), and unlike the companions of Procyon and Sirius it is not swamped in the glare of a much brighter primary.[21]

Nomenclature[edit | edit source]

40 Eridani is the system's Flamsteed designation and ο² Eridani (Latinised to Omicron² Eridani) its Bayer designation. The designations of the sub-components - 40 Eridani A, B and C - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[30] 40 Eridani C also bears the variable star designation DY Eridani.

The system bore the traditional name Keid derived from the Arabic word قيض qayḍ meaning "(egg)shells" (cf. neighboring Beid "eggs"). In 2016, the IAU organized a Working Group on Star Names (WGSN)[31] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[32] It approved the name Keid for the component 40 Eridani A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[25]

Properties[edit | edit source]

40 Eridani A is a main-sequence dwarf of spectral type K1, 40 Eridani B is a 9th magnitude white dwarf of spectral type DA4, and 40 Eridani C is an 11th magnitude red dwarf flare star of spectral type M4.5e. When component B was a main-sequence star, it is thought to have been the most massive member of the system, but ejected most of its mass before it became a white dwarf.[citation needed] B and C orbit each other approximately 400 AU from the primary star, A.[13] Their orbit has a semimajor axis of 35 AU (which is the approximate average distance between B and C) and is rather elliptical (eccentricity 0.410).[12]

As seen from the 40 Eridani system, the Sun is a 3.4-magnitude star in Hercules, near the border with Serpens Caput.[note 2]-->

Potential for life[edit | edit source]

Comparison of the habitable zones of the Sun and 40 Eridani A (here labeled Vulcan, after the fictional planet from Star Trek)

The habitable zone of 40 Eridani A, where a planet could exist with liquid water, is near 0.68 AU from A. At this distance a planet would complete a revolution in 223 Earth days (according to the third of Kepler's laws) and 40 Eridani A would appear nearly 20%[note 3] wider than the Sun does on Earth. An observer on a planet in the 40 Eridani A system would see the B/C pair as unusually bright (magnitudes -8 and -6) white and reddish-orange stars in the night sky.

It is unlikely that habitable planets exist around 40 Eridani B because they would have been sterilized by its evolution into a white dwarf. As for 40 Eridani C, it is prone to flares, which cause large momentary increases in the emission of X-rays as well as visible light. This would be lethal to Earth-type life on planets near the flare star.[13]

Planetary system[edit | edit source]

In 2018, a planet was discovered orbiting 40 Eridani A with a minimum mass of 8.47±0.47 Earth masses.[33] The planet has an orbit of 42 days, and lies considerably interior to the habitable zone, receiving 9 times more stellar flux than Earth, which is an even greater stellar flux amount than Mercury, the innermost planet in our solar system, on average receives from our Sun. It is one of the closest Super-Earths known, the closest discovered to date (as of 2 October 2018) within a multiple star system.[citation needed]


See also[edit | edit source]

Notes[edit | edit source]

  1. ^ From L=R2(Teff/5772)4, where L is the luminosity in units of L☉, R is the radius in units of R☉, Teff is the effective surface temperature in Kelvin, and 5772 is the nominal effective temperature of the sun
  2. ^ From 40 Eridani the Sun would appear on the diametrically opposite side of the sky at the coordinates RA= 16h 15m 16.32s, Dec=07° 39′ 10.34″, which is located near the border of Hercules (constellation) and Serpens Caput, the closest bright star being Alpha Serpentis. The absolute magnitude of the Sun is 4.85, so, at a distance of 5.04 parsecs, the Sun would have an apparent magnitude

References[edit | edit source]

  1. ^ a b c d e f g van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752 Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC-2); CDS ID I/289.
  3. ^ a b c d e f g h i Gliese Catalogue of Nearby Stars, preliminary 3rd ed., 1991. CDS ID V/70A.
  4. ^ a b Salim, Samir; Gould, Andrew (2003). "Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog". The Astrophysical Journal. 582 (2): 1011–1031. arXiv:astro-ph/0206318 Freely accessible. Bibcode:2003ApJ...582.1011S. doi:10.1086/344822. ; CDS ID J/ApJ/582/1011.
  5. ^ Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770 Freely accessible. Bibcode:2006AJ....132..161G. doi:10.1086/504637. 
  6. ^ General Catalogue of Trigonometric Parallaxes, 4th ed., 1995. CDS ID I/238A.
  7. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published In: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S. 
  8. ^ a b c HD 26965, database entry, Geneva-Copenhagen Survey of Solar neighbourhood, J. Holmberg et al., 2007, CDS ID V/117A, accessed on line November 19, 2008; described in Nordström, B; Mayor, M; Andersen, J; Holmberg, J; Pont, F; Jørgensen, B. R; Olsen, E. H; Udry, S; Mowlavi, N (2004). "The Geneva-Copenhagen survey of the Solar neighbourhood". Astronomy & Astrophysics. 418 (3): 989–1019. arXiv:astro-ph/0405198 Freely accessible. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. 
  9. ^ Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982 Freely accessible, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191. 
  10. ^ Evans, D. S (1967). "The Revision of the General Catalogue of Radial Velocities". Determination of Radial Velocities and Their Applications. 30: 57. Bibcode:1967IAUS...30...57E. 
  11. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365 Freely accessible. Bibcode:2018A&A...616A...1G Freely accessible. doi:10.1051/0004-6361/201833051 Freely accessible.  Gaia DR2 record for this source at VizieR.
  12. ^ a b c Heintz, W. D. (1974). "Astrometric study of four visual binaries". Astronomical Journal. 79: 819. Bibcode:1974AJ.....79..819H. doi:10.1086/111614. 
  13. ^ a b c "40 (Omicron2) Eridani 3] at solstation.com". Retrieved 2018-02-06. 
  14. ^ a b c Mason, Brian D.; et al. (November 2017), "Binary Star Orbits. V. The Nearby White Dwarf/Red Dwarf Pair 40 Eri BC", The Astronomical Journal, 154 (5): 9, arXiv:1707.03635 Freely accessible, Bibcode:2017AJ....154..200M, doi:10.3847/1538-3881/aa803e, 200. 
  15. ^ a b Catalogue of nearest stars until 10pc, V. A. Zakhozhaj. Revised 1996. CDS ID V/101.
  16. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365 Freely accessible. Bibcode:2018A&A...616A...1G Freely accessible. doi:10.1051/0004-6361/201833051 Freely accessible.  Gaia DR2 record for this source at VizieR.
  17. ^ Cayrel de Strobel, G.; Hauck, B.; Francois, P.; Thevenin, F.; Friel, E.; Mermilliod, M.; Borde, S. (1992). "A catalogue of Fe/H determinations". Astronomy & Astrophysics (1991 ed.). 95: 273–336. Bibcode:1992A&AS...95..273C. 
  18. ^ a b Díaz, Matías R.; Jenkins, James S.; Tuomi, Mikko; Butler, R. Paul; Soto, Maritza G.; Teske, Johanna K.; Feng, Fabo; Shectman, Stephen A.; Arriagada, Pamela; Crane, Jeffrey D.; Thompson, Ian B.; Vogt, Steven S. (2018). "The test case of HD26965: Difficulties disentangling weak Doppler signals from stellar activity". The Astronomical Journal. 155 (3): 126. arXiv:1801.03970 Freely accessible. Bibcode:2018AJ....155..126D. doi:10.3847/1538-3881/aaa896. 
  19. ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal. 687 (2): 1264–1293. arXiv:0807.1686 Freely accessible. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785. 
  20. ^ Provencal, J. L.; Shipman, H. L.; Høg, Erik; Thejll, P. (1998). "Testing the White Dwarf Mass-Radius Relation with HIPPARCOS". The Astrophysical Journal. 494 (2): 759. Bibcode:1998ApJ...494..759P. CiteSeerX 10.1.1.44.7051 Freely accessible. doi:10.1086/305238. 
  21. ^ a b Keid Archived 2007-05-14 at the Wayback Machine, Jim Kaler, STARS web page, accessed 15/5/2007, 10/12/2011.
  22. ^ Finley, David S.; Koester, Detlev; Basri, Gibor (1997). "The Temperature Scale and Mass Distribution of Hot DA White Dwarfs". The Astrophysical Journal. 488 (1): 375–396. Bibcode:1997ApJ...488..375F. doi:10.1086/304668. 
  23. ^ Bond, Howard E.; Bergeron, P.; Bédard, A. (2017). "Astrophysical Implications of a New Dynamical Mass for the Nearby White Dwarf 40 Eridani B". The Astrophysical Journal. 848 (1): 16. arXiv:1709.00478 Freely accessible. Bibcode:2017ApJ...848...16B. doi:10.3847/1538-4357/aa8a63. 
  24. ^ Johnson, H. M.; Wright, C. D. (1983). "Predicted infrared brightness of stars within 25 parsecs of the sun". Astrophysical Journal Supplement Series. 53: 643. Bibcode:1983ApJS...53..643J. doi:10.1086/190905. 
  25. ^ a b c "Naming Stars". IAU.org. Retrieved 16 December 2017. 
  26. ^ Davis, George A. (1944). "The pronunciations, derivations, and meanings of a selected list of star names". Popular Astronomy. 52: 8–30. 
  27. ^ Herschel, William (1785). "Catalogue of Double Stars. By William Herschel, Esq. F. R. S". Philosophical Transactions of the Royal Society of London. 75: 40–126. Bibcode:1785RSPT...75...40H. doi:10.1098/rstl.1785.0006. JSTOR 106749. 
  28. ^ Van Den Bos, W. H. (1926). "The orbit and the masses of 40 Eridani BC". Bulletin of the Astronomical Institutes of the Netherlands. 3: 128. Bibcode:1926BAN.....3..128V. 
  29. ^ White Dwarfs, E. Schatzman, Amsterdam: North-Holland, 1958. , p. 1
  30. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 Freely accessible [astro-ph.SR]. 
  31. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016. 
  32. ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14. 
  33. ^ Ma, Bo; et al. (2018). "The first super-Earth Detection from the High Cadence and High Radial Velocity Precision Dharma Planet Survey". Monthly Notices of the Royal Astronomical Society. 480 (2): 2411. arXiv:1807.07098 Freely accessible. Bibcode:2018MNRAS.480.2411M. doi:10.1093/mnras/sty1933. 

External links[edit | edit source]

 

Coordinates: Sky map 04h 15m 16.32s, −07° 39′ 10.34″

Retrieved from "https://starfleetlogistics.shoutwiki.com/w/index.php?title=40_Eridani&oldid=3044"