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HD 87816

Coordinates: Sky map 10h 06m 07.21s, −52° 11′ 16.6″
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HD 87816
Location of HD 87816 (circled)
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]
Distance436 ± 1 ly
(133.6 ± 0.4 pc)
Absolute magnitude (MV)+0.876±0.013[3]
Details[3]
Mass2.41±0.10 M☉
Radius9.0±0.2 R☉
Luminosity45±1 L☉
Surface gravity (log g)2.860±0.096 cgs
Temperature4,989±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
SIMBADdata

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

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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 0.818, 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]

Artist's impression of HD 87816 viewed from its outer planet.
The HD 87816 planetary system[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

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  1. ^ a b "VSX: Detail for R Vel". AAVSO. Retrieved 2025-06-01.
  2. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b c d e f Ottoni, G.; Udry, S.; Ségransan, D.; Buldgen, G.; Lovis, C.; Eggenberger, P.; Pezzotti, C.; Adibekyan, V.; Marmier, M.; Mayor, M.; Santos, N. C.; Sousa, S. G.; Lagarde, N.; Charbonnel, C. (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. arXiv:2201.01528. Bibcode:2022A&A...657A..87O. doi:10.1051/0004-6361/202040078. ISSN 0004-6361. HD 87816's database entry at VizieR.
  4. ^ a b Adelman, Saul J. (2001). "On the Photometric Variability of Red Clump Giants". Baltic Astronomy. 10: 593–597. Bibcode:2001BaltA..10..593A. doi:10.1515/astro-2001-0404. ISSN 1021-6766.
  5. ^ a b Houk, Nancy (1978). "Michigan catalogue of two-dimensional spectral types for the HD stars". Ann Arbor: Dept. of Astronomy. Bibcode:1978mcts.book.....H. HD 87816's database entry at VizieR.
  6. ^ a b Gontcharov, G. A. (2006-11-01). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. doi:10.1134/S1063773706110065. ISSN 1562-6873. HD 87816's database entry at VizieR.
  7. ^ "HD 87816". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved June 1, 2024.
  8. ^ "Limiting Magnitude | COSMOS". astronomy.swin.edu.au. Retrieved 2025-06-01.
  9. ^ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from the original on 2013-12-03. Retrieved 2012-01-16.
  10. ^ a b c d Fontanet, E.; Udry, S.; Ségransan, D.; Figueira, P.; Barroso, J. A. Acevedo; Akinsanmi, B.; Attia, M.; Battley, M.; Bhatnagar, S. (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". arXiv:2505.14317.
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