# Delta Pavonis

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Observation data Constellation Epoch J2000      Equinox J2000 Location of δ Pavonis (circled) Pavo 20h 08m 43.60953s[1] −66° 10′ 55.4436″[1] 3.56[2] G8 IV[2] 0.45[3] 0.76[3] Suspected[citation needed] Radial velocity (Rv) –21.7 ± 0.9[2] km/s Proper motion (μ) RA: +1211.03[1] mas/yr Dec.: –1130.05[1] mas/yr Parallax (π) 163.71 ± 0.17[1] mas Distance 19.92 ± 0.02 ly (6.108 ± 0.006 pc) Absolute magnitude (MV) 4.62 Mass 0.991[4] M☉ Radius 1.22[4] R☉ Luminosity 1.22 ± 0.04[5] L☉ Surface gravity (log g) 4.26[6] cgs Temperature 5,604[6] K Metallicity [Fe/H] +0.33[6] dex Rotational velocity (v sin i) 1.0[5] km/s Age 6.6–6.9[7] Gyr CD-66 2367, GCTP 4754, GJ 780, HD 190248, HIP 99240, HR 7665, LHS 485, LTT 7946, LFT 1520, NSV 12790, SAO 254733.[2]

Delta Pavonis (δ Pav, δ Pavonis) is a star in the southern circumpolar constellation of Pavo. It has an apparent visual magnitude of 3.56,[2] making it a fourth-magnitude star that is visible to the naked eye from the southern hemisphere. Parallax measurements from the Hipparcos satellite yield an estimated distance of 19.92 light-years (6.11 parsecs) from Earth.[1] This makes it one of the nearest bright stars to the Solar System.

## Observations

It is a subgiant of spectral type G8 IV, meaning it is about to stop fusing hydrogen in its core and is starting the process of becoming a red giant. Because of that, Delta Pavonis is 22%[5] brighter than the Sun even though the effective temperature of its outer atmosphere is lower, at 5,604 K.[6] It has 99.1% of the Sun's mass and 122% of the Sun's radius. The surface convection zone extends downward to about 43.1% of the star's radius, but only contains 4.8% of the star's mass.[4]

Spectroscopic examination of this star shows that it has a higher abundance of elements heavier than helium (or metallicity, as astronomers call it) than does the Sun. This value is typically given in terms of the relative ratio of iron (chemical symbol Fe) to hydrogen (H) as compared to the Sun's atmosphere (iron being a relatively easy element to detect in a stellar atmosphere). For Delta Pavonis, the metallicity is about:

$\begin{smallmatrix}\left [ \frac{Fe}{H} \right ]\ =\ 0.33\end{smallmatrix}$

(This notation gives the logarithm of the iron-to-hydrogen ratio relative to the Sun.) This corresponds to a 214% abundance of iron in this star's atmosphere compared to the solar abundance. Past studies have shown a correlation between the heavy element abundance in stars and the presence of a planetary system,[8] suggesting Delta Pavonis has a greater than average probability of harboring planets. However, no planetary companions have yet been discovered in orbit around this star.[9]

The age of this star is in the range of 6.6–6.9 billion years old,[7] and the star's luminosity has increased 60% since it was a zero-age main-sequence star.[citation needed] It appears to be rotating slowly with a projected rotational velocity of 1.0 km s−1.[5]

## Distance

Delta Pavonis distance estimates

Source Parallax, mas Distance, pc Distance, ly Ref.
Woolley et al. (1970) 175 ± 7 5.71+0.24
−0.22
18.6+0.8
−0.7
[10]
Gliese & Jahreiß (1991) 175.2 ± 8.2 5.71+0.28
−0.26
18.6+0.9
−0.8
[11]
van Altena et al. (1995) 174.9 ± 9.7 5.72+0.34
−0.3
18.6+1.1
−1
[12]
Perryman et al. (1997) (Hipparcos) 163.73 ± 0.65 6.108 ± 0.024 19.92 ± 0.08 [13]
Perryman et al. (1997) (Tycho) (absents) [14]
van Leeuwen (2007) 163.71 ± 0.17 6.108 ± 0.006 19.923 ± 0.021 [15]
RECONS TOP100 (2012) 163.71 ± 0.17[nb 1] 6.108 ± 0.006 19.923 ± 0.021 [16]

Non-trigonometric distance estimates are marked in italic. The best estimate is marked in bold.

## SETI

It has been identified by Maggie Turnbull and Jill Tarter of the SETI Institute as the "Best SETI target" among the list of the 100 nearest 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. The lack of detected radial velocity variation suggests that there are no gas giant planets orbiting near the star's habitable zone, which may otherwise destabilize a hypothetical Earth-like planet in that orbital zone. As of 1999, no radio source of technological origin has been detected coming from this star.[17] Delta Pavonis is the nearest solar analog that is not a member of a binary or multiple star system. This is a type of star that is a close photometric match to the Sun.[9]

## References

1. van Leeuwen, F. (November 2007), Validation of the new Hipparcos reduction, Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
2. "NSV 12790 -- Variable Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2009-08-21.
3. ^ a b Cousins, A. W. J.; Stoy, R. H. (1962). "Photoelectric magnitudes and colours of Southern stars". Royal Observatory Bulletins 64: 103–248.
4. ^ a b c Takeda, G.; Ford, E. B.; Sills, A.; Rasio, F. A.; Fischer, D. A.; Valenti, J. A.; Ford; Sills; Rasio; Fischer; Valenti (November 2008). "Stellar parameters of nearby cool stars (Takeda+, 2007)". VizieR On-line Data Catalog 216: 80297. Bibcode:2008yCat..21680297T. J/ApJS/168/297. Originally published in: 2007ApJS..168..297T.
5. ^ a b c d Bruntt, H. et al. (July 2010), Accurate fundamental parameters for 23 bright solar-type stars, Monthly Notices of the Royal Astronomical Society 405 (3): 1907–1923, arXiv:1002.4268, Bibcode:2010MNRAS.405.1907B, doi:10.1111/j.1365-2966.2010.16575.x
6. ^ a b c d Sousa, S. G. et al. (August 2008). "Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes". Astronomy and Astrophysics 487 (1): 373–381. arXiv:0805.4826. Bibcode:2008A&A...487..373S. doi:10.1051/0004-6361:200809698. See VizieR catalogue J/A+A/487/373.
7. ^ 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.
8. ^ 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.
9. ^ a b 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.
10. ^ Woolley R.; Epps E. A.; Penston M. J.; Pocock S. B. (1970). "Woolley 780". Catalogue of stars within 25 parsecs of the Sun. Retrieved 2014-11-21.
11. ^ Gliese, W. and Jahreiß, H. (1991). "Gl 780". Preliminary Version of the Third Catalogue of Nearby Stars. Retrieved 2014-11-21.
12. ^ Van Altena W. F., Lee J. T., Hoffleit E. D. (1995). "GCTP 4754". The General Catalogue of Trigonometric Stellar Parallaxes, Fourth Edition. Retrieved 2014-11-21.
13. ^ Perryman et al. (1997). "HIP 99240". The Hipparcos and Tycho Catalogues. Retrieved 2014-11-21.
14. ^ Perryman et al. (1997). "HIP 99240". The Hipparcos and Tycho Catalogues. Retrieved 2014-11-21.
15. ^ van Leeuwen F. (2007). "HIP 99240". Validation of the new Hipparcos reduction. Retrieved 2014-11-21.
16. ^ "RECONS TOP100". THE ONE HUNDRED NEAREST STAR SYSTEMS brought to you by RECONS (Research Consortium On Nearby Stars). 2012. Retrieved 2014-11-21.
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.

## Notes

1. ^ Weighted parallax based on parallaxes from van Altena et al. (1995) and van Leeuwen (2007).