HD 221287

HD 221287 / Poerava

Observation data Epoch J2000      Equinox J2000
Constellation	Tucana
Right ascension	23^h 31^m 20.33819^s[1]
Declination	−58° 12′ 35.0324″[1]
Apparent magnitude (V)	7.82[2]
Characteristics
Spectral type	F7V[3]
B−V color index	0.513±0.008[2]
Astrometry
Radial velocity (Rv)	−21.90±0.18[1] km/s
Proper motion (μ)	RA: 181.160±0.059[1] mas/yr Dec.: −5.297±0.060[1] mas/yr
Parallax (π)	17.8529 ± 0.0402 mas[1]
Distance	182.7 ± 0.4 ly (56.0 ± 0.1 pc)
Absolute magnitude (MV)	4.11[2]
Details[4]
Mass	1.209+0.034 −0.038 M☉
Radius	1.183+0.020 −0.019 R☉
Luminosity	1.944+0.005 −0.007[1] L☉
Surface gravity (log g)	4.374±0.013 cgs
Temperature	6,440±100 K
Metallicity [Fe/H]	+0.13±0.149 dex
Rotation	5±2[5]
Rotational velocity (v sin i)	2.9±0.2 km/s
Age	763+613 −474[4] or 1,300[5] Myr
Other designations
Poerava, CD−58°8579, HD 221287, HIP 116084, SAO 247912, TYC 8838-463-1, 2MASS J23312032-5812350[6]
Database references
SIMBAD	data

HD 221287, named Poerava, is a star in the southern constellation of Tucana. It has a yellow-white hue but is too faint to be viewed with the naked eye, having an apparent visual magnitude of 7.82.^[2] This object is located at a distance of 183 light years from the Sun, as determined from its parallax. It is drifting closer with a radial velocity of −22 km/s.^[1]

This object is an F-type main-sequence star with a stellar classification of F7V.^[3] It is relatively young with age estimates of 763^[4] million and 1.3 billion years, and possesses an active chromosphere. Cool spots on the surface are generating a radial-velocity signal that is modulated by the rotation period of around five days.^[5] The star is 18% larger and 20% more massive than the Sun.^[4] It is radiating 1.9^[1] times the luminosity of the Sun from its photosphere at an effective temperature of 6,440 K.^[4]

Name

The star was given the designation "HD 221287" before being named Poerava by representatives of the Cook Islands in the IAU's 2019 NameExoWorlds contest, with the comment "Poerava is the word in the Cook Islands Maori language for a large mystical black pearl of utter beauty and perfection."^[7]

Planetary system

On March 5, 2007, the astronomer Dominique Naef used the HARPS spectrograph to uncover the exoplanetary companion designated HD 221287 b (among others).^[5] Using the amplitude from observations with HARPS, he calculated a minimum mass of 3.12 times that of Jupiter, making this a superjovian. This planet orbits 25% further from the star than Earth is from the Sun, with a low eccentricity.

Stability analysis reveals that the orbits of Earth–sized planets in HD 221287 b's Trojan points, located 60 degrees ahead and behind the planet in its orbit, would be stable for long periods of time.^[8]

The HD 221287 planetary system^[5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b / Pipitea	>3.09±0.79 MJ	1.25±0.04	456.1±6.5	0.08±0.11	—	—

See also

• HD 100777
• HD 164595
• HD 190647

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
3. Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars. Vol. 1. Ann Arbor: Dept. of Astronomy, University of Michigan. Bibcode:1975mcts.book.....H.
4. Soto, M. G.; Jenkins, J. S. (July 2018). "Spectroscopic Parameters and atmosphEric ChemIstriEs of Stars (SPECIES). I. Code description and dwarf stars catalogue". Astronomy & Astrophysics. 615: 28. arXiv:1801.09698. Bibcode:2018A&A...615A..76S. doi:10.1051/0004-6361/201731533. S2CID 119107228. A76.
5. Naef, M.; et al. (2007). "The HARPS search for southern extra-solar planets. IX. Exoplanets orbiting HD 100777, HD 190647, and HD 221287". Astronomy and Astrophysics. 470 (2): 721–726. arXiv:0704.0917. Bibcode:2007A&A...470..721N. doi:10.1051/0004-6361:20077361.
6. "HD 221287". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-11-08.
7. "Approved names (§ Cook Islands)". Name Exo Worlds. IAU. Retrieved 19 December 2019.
8. Schwarz, R.; et al. (November 2007). "Survey of the stability region of hypothetical habitable Trojan planets" (PDF). Astronomy and Astrophysics. 474 (3): 1023–1029. Bibcode:2007A&A...474.1023S. doi:10.1051/0004-6361:20077994.