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'''Delta Equulei''' (δ Equulei, δ Equ) is the second brightest [[star]] in the [[constellation]] [[Equuleus]]. Delta Equulei is a [[binary star]] system about 60 [[light year]]s away,<ref name="Muterspaugh2005"/> with components of class G0 and F5.<ref name="Illinois">{{cite web |publisher=[[University of Illinois]] Astronomy department |url=http://www.astro.uiuc.edu/~kaler/sow/deltaequ.html |title=Delta Equulei}}</ref> Their combined [[Apparent magnitude|magnitude]] is 4.47, and their [[absolute magnitude]] is 3.142. There is controversy as to the exact masses of the stars. One study puts the larger at 1.22 [[solar mass]]es and the smaller at 1.17, while another pegs them at 1.66 and 1.593.<ref name="Illinois"/> The luminosity of the larger star is calculated to be 2.23 solar, and the smaller to be 2.17.<ref name="Illinois"/>
'''Delta Equulei''' (δ Equulei, δ Equ) is the second brightest [[star]] in the [[constellation]] [[Equuleus]]. Delta Equulei is a [[binary star]] system about 60 [[light year]]s away,<ref name="Muterspaugh2005"/> with components of class G0 and F5.<ref name="Illinois">{{cite web|publisher=[[University of Illinois]] Astronomy department |url=http://www.astro.uiuc.edu/~kaler/sow/deltaequ.html |title=Delta Equulei |deadurl=yes |archiveurl=https://web.archive.org/web/20061216035035/http://www.astro.uiuc.edu:80/%7Ekaler/sow/deltaequ.html |archivedate=2006-12-16 |df= }}</ref> Their combined [[Apparent magnitude|magnitude]] is 4.47, and their [[absolute magnitude]] is 3.142. There is controversy as to the exact masses of the stars. One study puts the larger at 1.22 [[solar mass]]es and the smaller at 1.17, while another pegs them at 1.66 and 1.593.<ref name="Illinois"/> The luminosity of the larger star is calculated to be 2.23 solar, and the smaller to be 2.17.<ref name="Illinois"/>


==System==
==System==

Revision as of 14:25, 10 December 2016

Delta Equulei
Observation data
Epoch J2000      Equinox J2000
Constellation Equuleus
Right ascension 21h 14m 28.815s[1]
Declination +10° 00′ 25.13″[1]
Apparent magnitude (V) 4.49 / 5.4
Characteristics
Spectral type F5V+ / G0
U−B color index −0.01
B−V color index 0.5
Variable type None
Astrometry
Radial velocity (Rv)–15.4 km/s
Proper motion (μ) RA: 42.39 ± 0.68[1] mas/yr
Dec.: –304.19 ± 0.42[1] mas/yr
Parallax (π)54.39 ± 0.15 mas[2]
Distance60.0 ± 0.2 ly
(18.39 ± 0.05 pc)
Absolute magnitude (MV)4.99
Details
Mass1.22 / 1.17 M☉
Radius1.19 / 0.525 R☉
Luminosity2.23 / 2.17 L☉
Age1.6 – 2.8 billion years
Orbit
CompanionDelta Equulei B
Period (P)5.7 yr
Semi-major axis (a)0.26″
Eccentricity (e)0.42
Inclination (i)100°
Longitude of the node (Ω)23°
Periastron epoch (T)1912.77
Other designations
del Equ, 7 Equ, HD 202275, LTT 16227, GJ 822.0, HIP 104858, BD+09°4746, HR 8123, SAO 126643
Database references
SIMBADdata

Delta Equulei (δ Equulei, δ Equ) is the second brightest star in the constellation Equuleus. Delta Equulei is a binary star system about 60 light years away,[2] with components of class G0 and F5.[3] Their combined magnitude is 4.47, and their absolute magnitude is 3.142. There is controversy as to the exact masses of the stars. One study puts the larger at 1.22 solar masses and the smaller at 1.17, while another pegs them at 1.66 and 1.593.[3] The luminosity of the larger star is calculated to be 2.23 solar, and the smaller to be 2.17.[3]

System

William Herschel listed Delta Equulei as a wide binary. Friedrich Georg Wilhelm von Struve later showed this to be an unrelated optical double star. However his son Otto Wilhelm von Struve while making follow-up observations in 1852 found that while the separation of the optical double continued to increase, Delta Equulei itself appeared elongated. He concluded that it is a much more compact binary.[4]

References

  1. ^ a b c d van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ a b Muterspaugh, Matthew W.; Lane, Benjamin F.; Konacki, Maciej; Burke, Bernard F.; Colavita, M. M.; Kulkarni, S. R.; Shao, M. (2005). "PHASES High-Precision Differential Astrometry of δ Equulei". The Astronomical Journal. 130 (6): 2866–2875. arXiv:astro-ph/0507585. Bibcode:2005AJ....130.2866M. doi:10.1086/497035. {{cite journal}}: Unknown parameter |displayauthors= ignored (|display-authors= suggested) (help)
  3. ^ a b c "Delta Equulei". University of Illinois Astronomy department. Archived from the original on 2006-12-16. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  4. ^ Struve, Otto Wilhelm (1859). "On some lately discovered Double Stars" (PDF). Monthly Notices of the Royal Astronomical Society. 20: 8. Bibcode:1859MNRAS..20....8S. doi:10.1093/mnras/20.1.8.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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