HD 87816
Star in the constellation Vela
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HD 87816 is a star in the constellation Vela. With an apparent magnitude of 6.499,[3] it is very close to the average threshold for naked eye visibility, and can only be viewed from sufficiently dark skies, far from light pollution.[8] Based on parallax measurements, it lies at a distance of 436 light-years.[2] It is moving away from the Solar System at a velocity of 4.7 km/s.[6]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Vela[1] |
| Right ascension | 10h 06m 07.21043s[2] |
| Declination | −52° 11′ 16.5788″[2] |
| Apparent magnitude (V) | 6.499±0.009[3] |
| Characteristics | |
| Evolutionary stage | Red clump[4] |
| Spectral type | K1III[5] |
| B−V color index | 0.986[3] |
| Astrometry | |
| Radial velocity (Rv) | 4.7±0.4[6] km/s |
| Proper motion (μ) | RA: −55.682 mas/yr[2] Dec.: +16.413 mas/yr[2] |
| Parallax (π) | 7.4825±0.0196 mas[2] |
| Distance | 436 ± 1 ly (133.6 ± 0.4 pc) |
| Absolute magnitude (MV) | +0.876±0.013[3] |
| Details[3] | |
| Mass | 2.41±0.10 M☉ |
| Radius | 9.0±0.2 R☉ |
| Luminosity | 45±1 L☉ |
| Surface gravity (log g) | 2.860±0.096 cgs |
| Temperature | 4,989±46 K |
| Metallicity [Fe/H] | +0.139±0.035 dex |
| Other designations | |
| R Vel (obsolete), CD−51°4471, HD 87816, HIP 49477, HR 3978, TYC 8194-294-1[7] | |
| Database references | |
| SIMBAD | data |
The spectrum of this star matches a spectral class of K1III,[5] with the luminosity class III indicating it is a giant star that has exhausted the hydrogen at its core. It is now fusing helium, being in the evolutionary stage known as the horizontal branch.[4] The star has 2.4 times the Sun's mass, having grown to a radius 9.0 times the radius of the Sun. It shines with 45 times the Sun's luminosity at an effective temperature of 4,989 K.[3] The temperature gives it the orange hue typical of K-type stars.[9]
HD 87816 was once believed to be a variable star and received the variable-star designation R Velorum, but it is now considered a constant star.[1]
Planetary system
HD 87816 hosts two known exoplanets, discovered in 2025 via Doppler spectroscopy. Both are gas giants, like Jupiter and Saturn.[10]
Planet b has a minimum mass of 6.7 Jupiter masses (MJ). It takes 484 days (1.33 years) to complete an orbit around HD 87816 and has a very high orbital eccentricity of 0.78, among the highest of exoplanets orbiting giant stars.[10]
Planet c has a minimum mass of 12.2 Jupiter masses. It takes 7,600 days (21 years) to complete an orbit around its host, and has a low eccentricity of 0.11.[10]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥6.74±0.13 MJ | 1.618±0.0003 | 1.3256+0.00036 −0.00033 |
0.780±0.005 | — | — |
| c | ≥12.20+2.15 −1.59 MJ |
10.14+0.99 −0.48 |
20.80+3.1 −1.46 |
0.19±0.07 | — | — |