Delta Microscopii

δ Microscopii, Latinised as Delta Microscopii, is a faint, orange hued binary star system in the constellation Microscopium, marking the eyepiece end of the "microscope".[8] It is just visible to the naked eye with an apparent visual magnitude of +5.68.[2] Based upon an annual parallax shift of 10.82 mas as seen from the Earth,[1] it is roughly 300 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.142 due to interstellar dust.[6]

Delta Microscopii
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Microscopium
Right ascension  20h 06m 01.14597s[1]
Declination −30° 07′ 30.4290″[1]
Apparent magnitude (V) 5.68[2]
Characteristics
Spectral type K0/1 III[3]
B−V color index +1.03[2]
Astrometry
Proper motion (μ) RA: +33.46[1] mas/yr
Dec.: −67.91[1] mas/yr
Parallax (π)10.82 ± 0.64[1] mas
Distance300 ± 20 ly
(92 ± 5 pc)
Absolute magnitude (MV)+0.87[4]
Orbit[5]
Period (P)1,599.3±8.15 d
Eccentricity (e)0.2
Periastron epoch (T)2453878.5 ± 3.59 JD
Argument of periastron (ω)
(secondary)		194.4±2.40°
Semi-amplitude (K1)
(primary)		5,581.3±5.42 km/s
Details[6]
δ Mic A
Mass1.96 M☉
Radius10.87 R☉
Luminosity57 L☉
Surface gravity (log g)2.45 cgs
Temperature4,805 K
Metallicity [Fe/H]0.03±0.11 dex
Rotational velocity (v sin i)2.12 km/s
Other designations
δ Mic, CD−39° 14089, FK5 3683, HD 200718, HIP 104148, HR 8070, SAO 212709[7]
Database references
SIMBADdata

This is a single-lined spectroscopic binary with an orbital period of 4.4 years and an eccentricity of 0.2.[5] The visible component is an evolved K-type giant star with a stellar classification of K0/1 III.[3] It is currently on the horizontal branch and thus is generating energy through helium fusion at its core.[6] Delta Microscopii has nearly twice the mass of the Sun and has expanded to 11 times the Sun's radius. The star is radiating 57 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,805 K.[6]

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.
  2. Lake, R. (1965), "Photometric Magnitudes and Colours for Bright Southern Stars (Sixth List)", Monthly Notes of the Astron. Soc. Southern Africa, 24: 41, Bibcode:1965MNSSA..24...41L.
  3. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1982mcts.book.....H.
  4. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  5. Bluhm, P.; et al. (2016), "New spectroscopic binary companions of giant stars and updated metallicity distribution for binary systems", Astronomy & Astrophysics, 593: A133, arXiv:1608.08260, Bibcode:2016A&A...593A.133B, doi:10.1051/0004-6361/201628459.
  6. Jones, M. I.; et al. (December 2011), "Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. I. Sample definition and physical properties", Astronomy & Astrophysics, 536: 7, arXiv:1110.6459, Bibcode:2011A&A...536A..71J, doi:10.1051/0004-6361/201117887, A71.
  7. "del Mic". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-12.
  8. Ridpath, Ian, "Microscopium", Star Tales, retrieved 2017-08-14.
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