65 Ursae Majoris
65 Ursae Majoris, abbreviated as 65 UMa, is a star system in the constellation of Ursa Major. With a combined apparent magnitude of about 6.5, it is at the limit of human eyesight and is just barely visible to the naked eye in ideal conditions. It is about 760 light years away from Earth.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| 65 UMa ABC | |
| Right ascension | 11h 55m 05.74925s |
| Declination | +46° 28′ 36.6408″ |
| Apparent magnitude (V) | +6.54 (A/B/C = 6.7 / 8.5 / 8.32) |
| 65 UMa D | |
| Right ascension | 11h 55m 11.33152s |
| Declination | +46° 28′ 11.2150″ |
| Apparent magnitude (V) | +6.965 |
| Characteristics | |
| 65 UMa ABC | |
| Spectral type | A7 / A7 / A3 / ? / ? |
| U−B color index | +0.08 |
| B−V color index | +0.11 |
| Variable type | Algol |
| 65 UMa D | |
| Spectral type | A0p |
| U−B color index | +0.01 |
| B−V color index | +0.02 |
| Astrometry | |
| 65 UMa ABC | |
| Radial velocity (Rv) | −3.90±4.4 km/s |
| Proper motion (μ) | RA: 10.41 mas/yr Dec.: 2.38 mas/yr |
| Parallax (π) | 4.72 ± 0.58 mas |
| Distance | approx. 690 ly (approx. 210 pc) |
| Absolute magnitude (MV) | −0.05 |
| 65 UMa D | |
| Radial velocity (Rv) | −7.00±3.7 km/s |
| Proper motion (μ) | RA: 11.82 mas/yr Dec.: 0.39 mas/yr |
| Parallax (π) | 3.37 ± 0.56 mas |
| Distance | approx. 1,000 ly (approx. 300 pc) |
| Absolute magnitude (MV) | −0.1 |
| Orbit | |
| Primary | 65 UMa Aa1 |
| Companion | 65 UMa Aa2 |
| Period (P) | 1.73043 d |
| Inclination (i) | 86.5±0.2° |
| Semi-amplitude (K1) (primary) | 133.3±4.2 km/s |
| Semi-amplitude (K2) (secondary) | 135.7±4.2 km/s |
| Orbit | |
| Primary | 65 UMa Aa |
| Companion | 65 UMa Ab |
| Period (P) | 641.5±16.7 |
| Eccentricity (e) | 0.169±0.048 |
| Inclination (i) | 47° |
| Semi-amplitude (K1) (primary) | 13.7 km/s |
| Semi-amplitude (K2) (secondary) | 19.9±2.7 km/s |
| Orbit | |
| Primary | 65 UMa A |
| Companion | 65 UMa B |
| Period (P) | 118.209±0.690 yr |
| Semi-major axis (a) | 208.2±9.7 mas |
| Eccentricity (e) | 0.504±0.006 |
| Inclination (i) | 38.1±2.4° |
| Longitude of the node (Ω) | 92.1±4.2° |
| Periastron epoch (T) | 2447516.9±126.8 |
| Argument of periastron (ω) (secondary) | 202.7±1.3° |
| Details | |
| 65 UMa Aa1 | |
| Mass | 1.74±0.06 M☉ |
| Radius | 1.86±0.08 R☉ |
| Temperature | 8,000 K |
| 65 UMa Aa2 | |
| Mass | 1.71±0.06 M☉ |
| Radius | 1.81±0.08 R☉ |
| Temperature | 7,948±20 K |
| 65 UMa Ab | |
| Mass | 2.4±0.4 M☉ |
| 65 UMa B | |
| Mass | 2.4±2.0 M☉ |
| 65 UMa C | |
| Mass | 2.01 M☉ |
| 65 UMa D | |
| Mass | 2.31(3.02 + 1.64) M☉ |
| Radius | 2.93 R☉ |
| Luminosity | 79 L☉ |
| Surface gravity (log g) | 3.85 cgs |
| Temperature | 8,600 K |
| Age | 525 Myr |
| Other designations | |
| 65 UMa ABC: DN UMa, BD+47°1913, HD 103483, HIP 58112, HR 4560, SAO 43945 | |
| 65 UMa D: BD+47°1914, HD 103498, HIP 58117, HR 4561, SAO 43946 | |
| Database references | |
| 65 UMa AB | |
| 65 UMa C | |
| 65 UMa D | |
65 Ursae Majoris is a sextuple star system. It contains six stars in a hierarchical orbit where each star orbits its inner stars. Such systems are uncommon, with only a few sextuple stars known. Higher-multiplicity star systems are uncommon because they are less stable than their simpler counterparts, and often decay into smaller systems.
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