31 Pegasi

Star in the constellation Pegasus

31 Pegasi
Observation data Epoch J2000 Equinox J2000
Location of 31 Pegasi (circled)
Constellation	Pegasus
Right ascension	22^h 21^m 31.07511^s^[1]
Declination	12° 12′ 18.6628″^[1]
Apparent magnitude (V)	4.99^[2]
Characteristics
Spectral type	B2IV-Ve^[3]
U−B color index	-0.81^[2]
B−V color index	-0.10^[2]
Variable type	γ Cas
Astrometry

Radial velocity (R_v)	−5.30^[4] km/s
Proper motion (μ)	RA: +6.32^[1] mas/yr Dec.: +4.80^[1] mas/yr
Parallax (π)	2.01 ± 0.28 mas^[1]
Distance	approx. 1,600 ly (approx. 500 pc)
Absolute magnitude (M_V)	−3.61^[5]

Details^[6]

Mass	12.5±0.7 `M`_☉
Luminosity (bolometric)	27,925+4,360 −3,770 `L`_☉
Surface gravity (log g)	3.71±0.15 cgs
Temperature	23,890±740 K
Rotational velocity (v sin i)	98±8 km/s
Age	15.4±1.3^[7] Myr

Other designations
31 Peg, IN Peg, BD+11°4784, FK5 843, GC 31255, HD 212076, HIP 110386, HR 8520, SAO 107854^[8]
Database references
SIMBAD	data

31 Pegasi is a single^[9] star in the northern constellation of Pegasus. It is visible to the naked eye as a dim, blue-white hued point of light with a baseline apparent visual magnitude of 4.99.^[2] It is located approximately 1,600 light years away from the Sun based on parallax,^[1] but is drifting closer with a radial velocity of −5.3 km/s.^[4]

A light curve for IN Pegasi, plotted from *Hipparcos* data^[10]

This is a massive Be star with a stellar classification of B2IV-V.^[11] It is a γ Cas variable; a type of shell star with a circumstellar disc of gas surrounding the star at the equator, and ranges from 5.05 up to 4.85 in visual magnitude.^[12] It is spinning with a projected rotational velocity of 98 km/s, with the pole being inclined by an estimated angle of 26°±9° to the line of sight from the Earth.^[6] The star is 15.4^[7] million years old with 12.5^[6] times the mass of the Sun. It is radiating around 28,000 times the luminosity of the Sun from its photosphere at an effective temperature of 23,890 K.^[6]

References

^ ^a ^b ^c ^d ^e ^f Van Leeuwen, F. (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. S2CID 18759600. Vizier catalog entry
^ ^a ^b ^c ^d Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
^ Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050 (5th Revised ed.). Bibcode:1995yCat.5050....0H.
^ ^a ^b Gontcharov, G. A. (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. S2CID 119231169.
^ 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. Vizier catalog entry
^ ^a ^b ^c ^d Zorec, J.; et al. (2016). "Critical study of the distribution of rotational velocities of Be stars". Astronomy & Astrophysics. 595: A132. Bibcode:2016A&A...595A.132Z. doi:10.1051/0004-6361/201628760. hdl:11336/37946.
^ ^a ^b Tetzlaff, N.; et al. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". 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. S2CID 118629873. Vizier catalog entry
^ "31 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-07-01.
^ 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.
^ "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
^ Lesh, Janet Rountree (December 1968). "The Kinematics of the Gould Belt: an Expanding Group?". Astrophysical Journal Supplement. 17: 371. Bibcode:1968ApJS...17..371L. doi:10.1086/190179.
^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "General Catalogue of Variable Stars". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.

Constellation of Pegasus

Stars

Bayer	α (Markab) β (Scheat) γ (Algenib) δ (Alpheratz) ε (Enif) ζ (Homam) η (Matar) θ (Biham) ι κ λ μ (Sadalbari) ν ξ ο π¹ π² ρ σ τ (Salm) υ (Alkarab) φ χ ψ
Flamsteed	1 2 3 4 5 7 9 11 12 13 14 15 16 17 18 19 20 21 23 25 28 30 31 32 33 34 35 36 37 38 39 40 41 45 51 (Helvetios) 52 55 56 57 58 59 60 61 63 64 65 66 67 69 70 71 72 73 74 75 76 77 78 79 80 82 83 85 86 87 23 Psc 34 Vul
Variable	R S U W Z RU RV RZ SV TW TY AG AQ AT AU AV AW BB BH BK BO BP BX BY DH DI DY EE EF EQ EZ GT GX HN HO HP HR HX II IK IM IP KT KU LL LO LS MS MT NV NZ OY PT V342 V343 V354 V363 V372 V376 V391
HR	19 49 8116 8219 8221 8231 8250 8257 8258 8274 8292 8325 8341 8348 8358 8359 8364 8372 8391 8397 8412 8415 8435 8441 8455 8456 8458 8460 8461 8466 8475 8482 8491 8503 8514 8543 8555 8564 8587 8604 8605 8608 8631 8638 8642 8737 8784 8788 8792 8824 8831 8833 8838 8839 8873 8922 8942 8953 8970 9039 9055 9078 9109
HD	434 204603 205011 205422 205603 206689 206793 208897 209709 210890 211076 213025 215549 215733 219196 219828 220288 220773 221170 221493 225292
Other	BD+14 4559 (Solaris) BD +17 4708 BD +28 4211 GD 246 Gl 829 Gl 880 HAT-P-8 NGC 8 NGC 18 NGC 30 PG 2131+066 PG 2303+243 PSR B2127+11C PSR B2303+30 Q2343-BX418 WASP-10 WASP-21 (Tangra) WASP-52 (Anadolu) WASP-59 WASP-60 (Morava) X2127+119 3C 454.3

Exoplanets	51 Pegasi b WASP-10b BD+14 4559 b (Pirx) TOI-5678 b HD 209458 b HR 8799 b c d e

Star
clusters

Other	Balbinot 1 Messier 15

Nebulae

Other	Pease 1

Galaxies

NGC	1 2 9 14 15 16 22 23 26 41 42 52 7033 7034 7042 7043 7053 7056 7066 7068 7074 7085 7190 7217 7236 7237 7303 7315 7317 7318 7319 7320 7320c 7331 7332 7448 7454 7457 7469 7479 7610 7619 7625 7673 7674 7678 7720 7741 7742 NGC 7752 NGC 7753 7767 7773 7800 7814
Other	BX442 CTA-102 Einstein Cross Huchra's lens IC 5337 Markarian 335 Pegasus Dwarf Irregular Galaxy Pegasus Dwarf Spheroidal Galaxy Q2343-BX418