Delta Pavonis

Delta Pavonis
Location of δ Pavonis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pavo
Right ascension 20h 08m 43.60887s[1]
Declination −66° 10′ 55.4428″[1]
Apparent magnitude (V) 3.56[2]
Characteristics
Spectral type G8 IV[3]
U−B color index 0.45[2]
B−V color index 0.76[2]
Variable type Suspected[4]
Astrometry
Radial velocity (Rv)−23.52±0.81[5] km/s
Proper motion (μ) RA: +1,211.761 mas/yr[1]
Dec.: –1,130.237 mas/yr[1]
Parallax (π)163.9544 ± 0.1222 mas[1]
Distance19.89 ± 0.01 ly
(6.099 ± 0.005 pc)
Absolute magnitude (MV)4.62[6]
Details[7]
Mass1.051±0.062[8] M☉
Radius1.197±0.016 R☉
Luminosity1.24±0.03 L☉
Surface gravity (log g)4.26±0.06 cgs
Temperature5,571±48 K
Metallicity [Fe/H]0.33±0.03 dex
Rotation21.4±9.3 d[9]
Rotational velocity (v sin i)0.32 km/s
Age6.6–6.9[10] Gyr
9.3[6] Gyr
Other designations
δ Pav, NSV 12790, CD−66 2367, GJ 780, HD 190248, HIP 99240, HR 7665, SAO 254733, LFT 1520, LHS 485, LTT 7946, 2MASS J20084376-6610563[11]
Database references
SIMBADdata

Delta Pavonis, Latinized from δ Pavonis, is a single[12] star in the southern constellation of Pavo. It has an apparent visual magnitude of 3.56,[11] making it a fourth-magnitude star that is visible to the naked eye from the southern hemisphere. Parallax measurements yield an estimated distance of 19.89 light-years (6.10 parsecs) from Earth.[1] This makes it one of the nearest bright stars to the Solar System. It is approaching the Sun with a radial velocity of −23.5 km/s, and is predicted to come as close as 17.8 light-years in around 49,200 years.[5]

Observations

This object is a subgiant of spectral type G8 IV; it will stop fusing hydrogen at its core relatively soon, starting the process of becoming a red giant. Hence, Delta Pavonis is 24% brighter than the Sun, but the effective temperature of its outer atmosphere is less: 5,571 K.[7] Its mass is 105% of Sol's mass, with a mean radius 120% of Sol's radius. Delta Pavonis's surface convection zone extends downward to about 43.1% of the star's radius, but only contains 4.8% of the star's mass.[13]

Spectroscopic examination of Delta Pavonis shows that it has a higher abundance of elements heavier than helium (metallicity) than does the Sun. This value is typically given in terms of the ratio of iron (chemical symbol Fe) to hydrogen (H) in a star's atmosphere, relative to that in Sol's atmosphere (iron being a good proxy for the presence of other heavy elements). The metallicity of Delta Pavonis is approximately

This notation gives the logarithm of the iron-to-hydrogen ratio, relative to that of the Sun, meaning that Delta Pavonis's iron abundance is 214% of that of Sol. It is considered super metal-rich, and the high metallicity has slowed its evolution.[14] Studies have shown a correlation between abundant heavy elements in stars, and the presence of a planetary system,[15] so Delta Pavonis has a greater than average probability of harboring planets.[14]

The age of Delta Pavonis is approximately 6.6 to 6.9 billion years,[10] and is certainly in the 5 to 7 billion year range.[14] It appears to be rotating slowly, with a projected rotational velocity of 0.32 kilometers per second.[7]

Possible planetary system

The existence of a Jupiter-mass gas giant on a long-period orbit around Delta Pavonis is suspected, as of 2021, based on astrometric data.[16] A study in 2023 detected a trend in the star's radial velocity, which may indicate the presence of a planetary companion, supporting the previous astrometric result. Such a planet would, at minimum, orbit with a period of 37 years at a distance of 11.1 AU, and have a mass at least 69 M🜨 (0.22 MJ).[9]

The Delta Pavonis planetary system[9]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
(unconfirmed) ≥69 M🜨 ≥11.1 ≥13,500 — — —

SETI

Delta Pavonis has been identified by Maggie Turnbull and Jill Tarter of the SETI Institute as the "Best SETI target" among the 100 closest G-type stars. Properties in its favor include a high metallicity, minimal level of magnetic activity, low rotation rate, and kinematic membership in the thin disk population of the Milky Way. Gas giants orbiting in, near, or through a star's habitable zone may destabilize the orbits of terrestrial planets in that zone; the lack of detected radial velocity variation suggests that there are no such gas giants orbiting Delta Pavonis. However, observation has detected no artificial radio sources.[17] Delta Pavonis, a close photometric match to the Sun, is the nearest solar analog that is not a member of a binary or multiple star system.[14]

References

  1. ^ 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.
  2. ^ a b c Cousins, A. W. J.; Stoy, R. H. (1962). "Photoelectric magnitudes and colours of Southern stars". Royal Observatory Bulletin. 64: 103–248. Bibcode:1962RGOB...64..103C.
  3. ^ Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  4. ^ Ruban, E. V.; et al. (September 2006), "Spectrophotometric observations of variable stars", Astronomy Letters, 32 (9): 604–607, Bibcode:2006AstL...32..604R, doi:10.1134/S1063773706090052, S2CID 121747360
  5. ^ a b Bailer-Jones, C.A.L.; et al. (2018). "New stellar encounters discovered in the second Gaia data release". Astronomy & Astrophysics. 616: A37. arXiv:1805.07581. Bibcode:2018A&A...616A..37B. doi:10.1051/0004-6361/201833456. S2CID 56269929.
  6. ^ a b Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
  7. ^ a b c Rains, Adam D.; et al. (April 2020). "Precision angular diameters for 16 southern stars with VLTI/PIONIER". Monthly Notices of the Royal Astronomical Society. 493 (2): 2377–2394. arXiv:2004.02343. Bibcode:2020MNRAS.493.2377R. doi:10.1093/mnras/staa282.
  8. ^ Pinheiro, F. J. G.; et al. (December 2014), "On the mass estimation for FGK stars: comparison of several methods", Monthly Notices of the Royal Astronomical Society, 445 (3): 2223–2231, Bibcode:2014MNRAS.445.2223P, doi:10.1093/mnras/stu1812, hdl:10316/80294.
  9. ^ a b c Laliotis, Katherine; Burt, Jennifer A.; et al. (February 2023). "Doppler Constraints on Planetary Companions to Nearby Sun-like Stars: An Archival Radial Velocity Survey of Southern Targets for Proposed NASA Direct Imaging Missions". The Astronomical Journal. 165 (4): 176. arXiv:2302.10310. Bibcode:2023AJ....165..176L. doi:10.3847/1538-3881/acc067. S2CID 257050346.
  10. ^ a b Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal. 687 (2): 1264–1293. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785. S2CID 27151456.
  11. ^ a b "NSV 12790 -- Variable Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2009-08-21.
  12. ^ Fuhrmann, K.; et al. (February 2017). "Multiplicity among Solar-type Stars". The Astrophysical Journal. 836 (1): 23. Bibcode:2017ApJ...836..139F. doi:10.3847/1538-4357/836/1/139. 139.
  13. ^ Takeda, G.; Ford, E. B.; Sills, A.; Rasio, F. A.; Fischer, D. A.; Valenti, J. A. (November 2008). "Stellar parameters of nearby cool stars (Takeda+, 2007)". VizieR On-line Data Catalog. 216: 80297. Bibcode:2008yCat..21680297T. doi:10.26093/cds/vizier.21680297. J/ApJS/168/297. Originally Published in: 2007ApJS..168..297T.
  14. ^ a b c d G. F. Porto de Mello; E. F. del Peloso; L. Ghezzi (2006). "Astrobiologically interesting stars within 10 parsecs of the Sun". Astrobiology. 6 (2): 308–331. arXiv:astro-ph/0511180. Bibcode:2006AsBio...6..308P. doi:10.1089/ast.2006.6.308. PMID 16689649. S2CID 119459291.
  15. ^ Sousa, S.G.; et al. (2006). "Spectroscopic parameters for a sample of metal-rich solar-type stars". Astronomy and Astrophysics. 458 (3): 873–880. Bibcode:2006A&A...458..873S. doi:10.1051/0004-6361:20065658.
  16. ^ Makarov, Valeri V.; et al. (2021). "Looking for Astrometric Signals below 20 m/s: A Candidate Exo-Jupiter in δ Pav". Research Notes of the AAS. 5 (5): 108. arXiv:2105.03244. Bibcode:2021RNAAS...5..108M. doi:10.3847/2515-5172/abfec9. ISSN 2515-5172.
  17. ^ M.C. Turnbull; J.C. Tarter (2003). "Target Selection for SETI. II. Tycho-2 Dwarfs, Old Open Clusters, and the Nearest 100 Stars". The Astrophysical Journal Supplement Series. 149 (2): 423–436. Bibcode:2003ApJS..149..423T. doi:10.1086/379320.

Further reading