Astronomy:Delta Mensae

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Star in the constellation Mensa
Delta Mensae
Observation data
Equinox J2000.0]] (ICRS)
Constellation Mensa
Right ascension  04h 17m 59.2718s[1]
Declination −80° 12′ 50.511″[1]
Apparent magnitude (V) 5.69[2]
Spectral type K2/3 III + A9[3]
U−B color index +0.53[2]
B−V color index +0.84[2]
Radial velocity (Rv)−20.0±4.3[4] km/s
Proper motion (μ) RA: +27.53[1] mas/yr
Dec.: +61.56[1] mas/yr
Parallax (π)7.70 ± 0.27[1] mas
Distance420 ± 10 ly
(130 ± 5 pc)
Absolute magnitude (MV)0.34[5]
δ Men A
Radius14[6] R
Luminosity92[7] L
Temperature5,183[5] K
Rotational velocity (v sin i)4.7±0.2[5] km/s
Other designations
δ Men, CPD−80° 116, FK5 166, HD 28525, HIP 20049, HR 1426, SAO 258372[8]
Database references

Delta Mensae (δ Mensae) is a binary star[9] system in the southern constellation of Mensa. It is faintly visible to the naked eye, having an apparent visual magnitude of 5.69.[2] Based upon an annual parallax shift of 7.70 mas as seen from the Earth,[1] it is 420 light years from the Sun.

The primary, designated component A, is a K-type giant star with a stellar classification of K2/3 III.[3] The measured angular diameter of this star is 1.00±0.01 mas,[10] which, at the estimated distance of this system, yields a physical size of about 14 times the radius of the Sun.[6] The star is radiating 92[7] times the Sun's luminosity from its photosphere at an effective temperature of 5,183 K.[5] Its companion, component B, is an A-type star about 0.9 magnitudes fainter than the primary.[3]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode2007A&A...474..653V. 
  2. 2.0 2.1 2.2 2.3 Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99), Bibcode1966CoLPL...4...99J. 
  3. 3.0 3.1 3.2 Parsons, Sidney B.; Ake, Thomas B. (November 1998), "Ultraviolet and Optical Studies of Binaries with Luminous Cool Primaries and Hot Companions. V. The Entire IUE Sample", The Astrophysical Journal Supplement Series 119 (1): 83–104, doi:10.1086/313152, Bibcode1998ApJS..119...83P. 
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics 546: 14, doi:10.1051/0004-6361/201219219, A61, Bibcode2012A&A...546A..61D. 
  5. 5.0 5.1 5.2 5.3 Ammler-von Eiff, M.; Reiners, A. (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics 542: 31, doi:10.1051/0004-6361/201118724, A116, Bibcode2012A&A...542A.116A. 
  6. 6.0 6.1 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1,  The radius (R*) is given by:
    [math]\displaystyle{ \begin{align} 2\cdot R_* & = \frac{(130\cdot 1.00\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 28\cdot R_{\bigodot} \end{align} }[/math]
  7. 7.0 7.1 McDonald, I. et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–57, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode2012MNRAS.427..343M. 
  8. "del Men". SIMBAD. Centre de données astronomiques de Strasbourg. 
  9. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode2008MNRAS.389..869E. 
  10. Richichi, A. et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431 (2): 773–777, doi:10.1051/0004-6361:20042039, Bibcode2005A&A...431..773R. 

Coordinates: Sky map 04h 17m 59.1s, −80° 12′ 50″