Pi2 Octantis

Pi2 Octantis, Latinized from π2 Octantis, is a solitary star situated in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.64, allowing it to be faintly visible to the naked eye under ideal conditions. Located 1,570 light years away, the star is approaching the Sun with a heliocentric radial velocity of −13.8 km/s. This object is an ageing late G-type supergiant that has 7 times the mass of the Sun and 69.02 times the radius of the Sun. It radiates at 2,709 L☉ from its enlarged photosphere at an effective temperature of 4,588 K, giving it an orange-yellow glow. Despite its advanced state, Pi2 Octantis is still a young star at an age of 43 million years. It spins modestly with a projected rotational velocity of 5.7 km/s.

Star in the constellation Octans

For other stars with this Bayer designation, see π Octantis.

π² Octantis

Location of π2 Octantis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	15h 04m 46.9232s[1]
Declination	−83° 02′ 17.920″[1]
Apparent magnitude (V)	5.64 ± 0.01[2]
Characteristics
Spectral type	G8 Ib[3]
U−B color index	+1.15[4]
B−V color index	+1.3[4]
Astrometry
Radial velocity (Rv)	−13.8 ± 0.3[5] km/s
Proper motion (μ)	RA: −8.312[1] mas/yr Dec.: −17.597[1] mas/yr
Parallax (π)	2.0741±0.0429 mas[1]
Distance	1,570 ± 30 ly (482 ± 10 pc)
Absolute magnitude (MV)	−3.19[6]
Details
Mass	7 ± 1[7] M☉
Radius	69.02+1.61 −1.53[8] R☉
Luminosity	2,709[9] L☉
Temperature	4,588[9] K
Rotational velocity (v sin i)	5.7 ± 1.8[10] km/s
Age	43 ± 3[7] Myr
Other designations
π2 Oct, 22 G. Octantis, CPD−82°636, GC 20145, HD 131246, HIP 73771, HR 5545, SAO 258714
Database references
SIMBAD	data

Pi² Octantis, Latinized from π² Octantis, is a solitary^[11] star situated in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.64, allowing it to be faintly visible to the naked eye under ideal conditions. Located 1,570 light years away,^[1] the star is approaching the Sun with a heliocentric radial velocity of −13.8 km/s.^[5]

This object is an ageing late G-type supergiant that has 7 times the mass of the Sun^[7] and 69.02 times the radius of the Sun.^[8] It radiates at 2,709 L_☉ from its enlarged photosphere at an effective temperature of 4,588 K,^[9] giving it an orange-yellow glow. Despite its advanced state, Pi² Octantis is still a young star at an age of 43 million years.^[7] It spins modestly with a projected rotational velocity of 5.7 km/s.^[10]

References

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1. ^ ^{a b c d e f} Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
2. ^ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
3. ^ Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations -90_ to -53_ƒ0. Bibcode:1975mcts.book.....H.
4. ^ ^{a b} Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1 January 1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
5. ^ ^{a b} Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. ISSN 1063-7737. S2CID 119231169.
6. ^ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 119257644.
7. ^ ^{a b c d} Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (1 January 2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun: Catalogue of young runaway stars". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. ISSN 0035-8711.
8. ^ ^{a b} 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.
9. ^ ^{a b c} McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711.
10. ^ ^{a b} De Medeiros, J. R.; Udry, S.; Burki, G.; Mayor, M. (November 2002). "A catalog of rotational and radial velocities for evolved stars: II. Ib supergiant stars". Astronomy & Astrophysics. 395 (1): 97–98. Bibcode:2002A&A...395...97D. doi:10.1051/0004-6361:20021214. ISSN 0004-6361.
11. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976