  | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 (ICRS) | |
|---|---|
| Constellation | Leo |
| Right ascension | 11h 36m 56.92983s[1] |
| Declination | +00° 49′ 25.8758″[1] |
| Apparent magnitude (V) | 4.33[2] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | G9 III[4] |
| U−Bcolor index | +0.76[2] |
| B−Vcolor index | +1.00[2] |
| Astrometry | |
| Radial velocity (Rv) | 1.79±0.16[5] km/s |
| Proper motion (μ) | RA: +1.76[1]mas/yr Dec.: +43.37[1]mas/yr |
| Parallax (π) | 17.97±0.22 mas[1] |
| Distance | 182 ± 2 ly (55.6 ± 0.7 pc) |
| Absolute magnitude (MV) | 0.59[6] |
| Details | |
| Mass | 2.58[6] M☉ |
| Radius | 11.38±0.16[7] R☉ |
| Luminosity | 56[5] L☉ |
| Surface gravity (log g) | 2.7[5] cgs |
| Temperature | 4,842[5] K |
| Metallicity[Fe/H] | –0.34[5] dex |
| Rotational velocity (v sin i) | 0.0[5] km/s |
| Age | 4.12±2.08[8] Gyr |
| Other designations | |
| υ Leo,91 Leo,BD−00°2458,FK5 437,HD 100920,HIP 56647,HR 4471,SAO 138298[9] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Upsilon Leonis (υ Leo) is astar in thezodiacconstellation ofLeo. It is visible to the naked eye with anapparent visual magnitude of 4.33.[2] The distance to this star, as determined usingparallax measurements,[1] is about 182 light years. At that distance, the visual magnitude of the star is diminished by an estimatedextinction factor of 0m.02 because ofinterstellar dust.[6]
With an age of around 4 billion years, this star hasevolved into aG-typegiant star with astellar classification of G9 III.[4] It has 2.6 times theSun's mass,[6] but has expanded to 11.4 times thesolar radius[7] and shines with 56 times theluminosity of the Sun at aneffective temperature of 4,842 K.[5] The rate of rotation is too small to be measured, with aprojected rotational velocity of 0.0 km/s.[5] The chemical abundance of elements other than hydrogen and helium, what astronomers term the star'smetallicity, is less than half that in the Sun.[5] It is most likely a member of the galacticthin disk population.[8]
In 2021, a gas giant planet was detected byradial velocity method.[10] In 2024, this object's true mass was measured usingastrometry from theGaia spacecraft. The method consists of taking the host star's RUWE level—an astrometirc indicator— from the astrometric solution. A large RUWE could imply that there is an unseen companion around the star, or that there are systematic calibration errors in the astrometric solution. Assuming the former scenario, the mass of Upsilon Leonis b is measured at29.2 MJ, indicating that it is a brown dwarf, but the latter scenario is still a possibility, which means that this measured mass is likely an upper limit.[11]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥0.51+0.06 −0.26[10] and ≤29.2[11] MJ | 1.18+0.11 −0.32 | 385.2+2.8 −1.3 | 0.320+0.134 −0.218 | — | — |
