HD 85945 (HR 3922) is a star in the constellation Ursa Major. It is a yellow giant star with a spectral type of G6III:Fe-0.5. Based on information from Gaia DR3, it is located 132.54 parsecs (432.3 ly) from Earth and is moving towards Earth at a velocity of 47 km/s. It has an apparent magnitude of 5.96, which makes it faintly visible to the naked eye.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major[a] |
| Right ascension | 09h 57m 13.61s[1] |
| Declination | +57° 25′ 05.54″[1] |
| Apparent magnitude (V) | 5.959±0.009[1] |
| Characteristics | |
| Evolutionary stage | Horizontal branch[2] |
| Spectral type | G6III:Fe-0.5[1] |
| Apparent magnitude (B) | 6.854±0.015[1] |
| Apparent magnitude (G) | 5.733[1] |
| Apparent magnitude (J) | 4.513±0.028[1] |
| Apparent magnitude (H) | 4.141±0.036[1] |
| Apparent magnitude (K) | 3.978±0.3[1] |
| B−V color index | 0.895[3] |
| Astrometry | |
| Radial velocity (Rv) | −46.55±0.12[4] km/s |
| Proper motion (μ) | RA: 31.347 mas/yr[4] Dec.: -61.766 mas/yr[4] |
| Parallax (π) | 7.4137 ± 0.024 mas[4] |
| Distance | 432.08 ly (132.54 pc)[4] |
| Absolute magnitude (MV) | 0.32[5] |
| Details | |
| Mass | 2.5[2] M☉ |
| Radius | 10.28±0.14[6] R☉ |
| Luminosity | 77.62[7][b] L☉ |
| Surface gravity (log g) | 2.6866[4] cgs |
| Temperature | 5281±22[6] K |
| Metallicity [Fe/H] | –0.4[7] dex |
| Rotational velocity (v sin i) | 7.53[3] km/s |
| Age | 660.7[2][c] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Characteristics
It is an evolved G-type giant star, based on its spectral type of G6III:Fe-0.5, which also indicates that is has a [Fe/H] metallicity of -0.5.[1] HD 85945 is 2.5 times more massive than the Sun and has expanded to 10.28 times the Sun's size.[2][6] It is emitting 78 times the solar luminosity from its photosphere at an effective temperature of 5,281 K.[7][6] Currently, the star is located in the horizontal branch stage of evolution.[2] The age of HD 85945 is estimated at 660 million years,[2] and it rotates under its axis at a speed of 7.53 km/s.[3] It is slightly metal-poor compared to the Sun, with an abundance of iron equivalent to 40% of the solar abundance.[7][d]
HD 85945 is located within the Ursa Major constellation, based on its celestial coordinates.[a] The distance to HD 85945 is of 132.54 parsecs (432.3 ly), based on spectra from Gaia DR3.[4] The apparent magnitude of the star is of 5.96,[1] which is brighter than the limiting magnitude for naked-eye vision (6.5m), making it faintly visible to the naked eye.[8] The absolute magnitude, i.e. the brightness of the star if it was seen at a distance of 10 parsecs (32.6 ly), is 0.32.[5] At the current distance, its brightness is diminished by 0.03 magnitudes due to interstellar extinction between Earth and the star.[6] HD 85945 is moving away from Earth at a velocity of 46.55 km/s.[4] It has a high proper motion in the sky.[6][1]