Astronomy:HD 87816
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| 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[2] mas/yr Dec.: +16.413[2] mas/yr |
| Parallax (π) | 7.4825 ± 0.0196[2] mas |
| 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 | |
| Database references | |
| SIMBAD | data |
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]
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 | — | — |
References
- ↑ 1.0 1.1 "VSX: Detail for R Vel". https://www.aavso.org/vsx/index.php?view=detail.top&oid=37417.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Ottoni, G.; Udry, S.; Ségransan, D.; Buldgen, G.; Lovis, C.; Eggenberger, P.; Pezzotti, C.; Adibekyan, V. et al. (2022-01-01). "CORALIE radial-velocity search for companions around evolved stars (CASCADES). I. Sample definition and first results: Three new planets orbiting giant stars". Astronomy and Astrophysics 657: A87. doi:10.1051/0004-6361/202040078. ISSN 0004-6361. Bibcode: 2022A&A...657A..87O. HD 87816's database entry at VizieR.
- ↑ 4.0 4.1 Adelman, Saul J. (2001). "On the Photometric Variability of Red Clump Giants" (in en). Baltic Astronomy 10 (4): 593–597. doi:10.1515/astro-2001-0404. ISSN 1021-6766. Bibcode: 2001BaltA..10..593A.
- ↑ 5.0 5.1 Houk, Nancy (1978). "Michigan catalogue of two-dimensional spectral types for the HD stars" (in en). Ann Arbor: Dept. Of Astronomy. Bibcode: 1978mcts.book.....H. HD 87816's database entry at VizieR.
- ↑ 6.0 6.1 Gontcharov, G. A. (2006-11-01). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system" (in en). Astronomy Letters 32 (11): 759–771. doi:10.1134/S1063773706110065. ISSN 1562-6873. Bibcode: 2006AstL...32..759G. HD 87816's database entry at VizieR.
- ↑ "HD 87816". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+87816.
- ↑ "Limiting Magnitude | COSMOS". https://astronomy.swin.edu.au/cosmos/l/Limiting+Magnitude.
- ↑ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html. Retrieved 2012-01-16.
- ↑ 10.0 10.1 10.2 10.3 Fontanet, E.; Udry, S.; Ségransan, D.; Figueira, P.; Barroso, J. A. Acevedo; Akinsanmi, B.; Attia, M.; Battley, M. et al. (2025-05-20). "CORALIE radial-velocity search for companions around evolved stars (CASCADES) IV: New planetary systems around HD 87816, HD 94890, and HD 102888 and an update on HD 121056". Astronomy and Astrophysics 699. doi:10.1051/0004-6361/202554137. Bibcode: 2025A&A...699A..38F.
Coordinates: 
10h 06m 07.21s, −52° 11′ 16.6″
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