Omicron Sagittarii

Omicron Sagittarii
Location of ο Sagittarii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension 19h 04m 40.98177s[1]
Declination −21° 44′ 29.3845″[1]
Apparent magnitude (V) +3.771[2]
Characteristics
Evolutionary stage horizontal branch[3]
Spectral type G9IIIb[4]
B−V color index +1.012±0.008[5]
Astrometry
Radial velocity (Rv)+26.1±0.6[5] km/s
Proper motion (μ) RA: +76.35±0.31[1] mas/yr
Dec.: −58.12±0.18[1] mas/yr
Parallax (π)22.96 ± 0.24 mas[1]
Distance142 ± 1 ly
(43.6 ± 0.5 pc)
Absolute magnitude (MV)0.625[2]
Details
Mass1.80[6] M☉
Radius12.09+0.29
−0.17[7] R☉
Luminosity66.7±1.1[7] L☉
Surface gravity (log g)2.66[2] cgs
Temperature4,744+34
−57 K
Metallicity [Fe/H]−0.04[2] dex
Age2.39[6] Gyr
Other designations
ο Sgr, 39 Sagittarii, BD−21°5237, GC 26224, HD 177241, HIP 93683, HR 7217, SAO 187643, PPM 269274, ADS 11996, CCDM J19047-2144A, WDS J19047-2144A[8]
Database references
SIMBADdata

ο Sagittarii, Latinized as Omicron Sagittarii, is a single[9] star in the constellation Sagittarius. It is yellow in hue and visible to the naked eye with an apparent visual magnitude of +3.77.[2] The distance to this star is approximately 142 light years based on parallax.[1] It is drifting further away from the Sun with a radial velocity of +26 km/s, having come to within 86 ly around a million years ago.[5]

This object is position 0.86 degrees north of the ecliptic, so ο Sagittarii can be occulted by the Moon and very rarely by planets. The last occultation by a planet took place on 24 December 1937, when it was occulted by Mercury.[citation needed] It was almost eclipsed by the sun, which occupies a mean, rounded, half of one degree of the sky, on 5 January.[10] Thus the star can be viewed the whole night, crossing the sky, in early July.

This is an aging giant star with a stellar classification of G9IIIb.[4] It is classified as a red clump giant, suggesting it is on the horizontal branch undergoing core helium fusion.[3] The star is 2.39[6] billion years old with 1.80[6] times the mass of the Sun. It has expanded to 12 times the girth of the Sun and is radiating 67 times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,744 K.[7]

It has a faint, magnitude 13.8 companion, designated component B and positioned 38.4″ away along a position angle of 252°, as of 2010.[11]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference Liu2007 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Alves2000 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Keenan1989 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference luck2015 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference skymap was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Mason2001 was invoked but never defined (see the help page).