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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. 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

[edit]

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

[edit]
  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 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. 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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