HD 200073

HD 200073 (HR 8046; 43 G. Microscopii) is a solitary star located in the southern constellation Microscopium 8.5′ northwest of Zeta Microscopii. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.94.^[2] The object is located relatively close at a distance of 227 light-years based on Gaia DR3 parallax measurements, but it is receding with a heliocentric radial velocity of 39 km/s.^[6] At its current distance, HD 200073's brightness is diminished by an interstellar extinction of 0.13 magnitudes^[15] and it has an absolute magnitude of +1.79.^[7] It has a relatively high proper motion across the celestial sphere, moving at a rate of 213 mas/yr.^[1]

HD 200073

Location of HD 200037 and ζ Microscopii on the map (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Microscopium
Right ascension	21h 02m 27.16546s[1]
Declination	−38° 31′ 51.4904″[1]
Apparent magnitude (V)	5.94[2]
Characteristics
Evolutionary stage	red giant branch[3]
Spectral type	K2 III[4] or K0 IV[5]
B−V color index	+1.15[2]
Astrometry
Radial velocity (Rv)	39±10[6] km/s
Proper motion (μ)	RA: +156.842 mas/yr[1] Dec.: −171.108 mas/yr[1]
Parallax (π)	14.358±0.0466 mas[1]
Distance	227.2 ± 0.7 ly (69.6 ± 0.2 pc)
Absolute magnitude (MV)	+1.79[7]
Details
Mass	1.03[8] M☉
Radius	9.15±0.46[9] R☉
Luminosity	28.8±0.3[1] L☉
Surface gravity (log g)	2.75[8] cgs
Temperature	4,569±50[10] K
Metallicity [Fe/H]	−0.13[8] dex
Rotational velocity (v sin i)	2.7±1.1[11] km/s
Age	8.79+2.32 −2.04[12] Gyr
Other designations
43 G. Microscopii[13], CD−39°14079, CPD−39°8841, GC 29351, HD 200073, HIP 103836, HR 8046, SAO 212653, TIC 115011683[14]
Database references
SIMBAD	data

HD 200073 has a stellar classification of K2 III,^[4] indicating that it is an evolved K-type giant that has exhausted hydrogen at its core and left the main sequence. Astronomer David Stanley Evans gave a class of K0 IV,^[5] indicating that it is a slightly evolved subgiant that is ceasing hydrogen fusion at its core. HD 200073 is currently on the red giant branch,^[3] fusing hydrogen in a shell around an inert helium core. It has a comparable mass to the Sun^[8] but at the age of 8.79 billion years,^[12] it has expanded to 9.15 times the radius of the Sun.^[9] It radiates 28.8 times the luminosity of the Sun^[1] from its enlarged photosphere at an effective temperature of 4,569 K.^[10] HD 200073 is slightly metal-deficient with an iron abundance of [Fe/H] = −0.13 or 74.1% of the Sun's.^[8] It spins modestly with a projected rotational velocity of 2.7 km/s.^[11]