HD 117440

HD 117440, also known by its Bayer designation d Centauri (d Cen), is a binary star in the constellation Centaurus. It is approximately 900 light years from Earth.

This article is about d Centauri. It is not to be confused with D Centauri.

d Centauri A/B

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Centaurus
Right ascension	13^h 31^m 02.66^s[1]
Declination	−39° 24′ 26.3″[1]
Apparent magnitude (V)	+4.5/+4.7
Characteristics
Spectral type	G8III/G9III
U−B color index	+1.03
B−V color index	+1.17
Variable type	none
Astrometry
Radial velocity (Rv)	−2 km/s
Proper motion (μ)	RA: -15.67 ± 0.47[1] mas/yr Dec.: -10.49 ± 0.31[1] mas/yr
Parallax (π)	3.60 ± 0.49[1] mas
Distance	approx. 900 ly (approx. 280 pc)
Absolute magnitude (MV)	−3.4/−3.2
Orbit[2]
Period (P)	83.14 ± 1.26 yr
Semi-major axis (a)	0.161 ± 0.004″
Eccentricity (e)	0.521 ± 0.013
Inclination (i)	145.2 ± 4.0°
Longitude of the node (Ω)	146.5 ± 8.6°
Periastron epoch (T)	B 1956.12 ± 1.91
Argument of periastron (ω) (secondary)	244.4 ± 3.6°
Other designations
HR 5089, HD 117440, CD−38°8592, HIP 65936, SAO 204545, GC 18254, CCDM J13310-3924
Database references
SIMBAD	data

Both components are yellow G-type giant stars. The primary, d Centauri A, has an apparent magnitude of +4.5, while the secondary, d Centauri B, has an apparent magnitude of +4.7. The two stars orbit around their common centre of mass once every 83 years and the secondary has a semi-major axis of 0.161 arcseconds.[2]

References

1. 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. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 21 May 2017.