Pi1 Pegasi

For other stars with this Bayer designation see π Pegasi
Pi1 Pegasi
Location of π2 Pegasi (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus
Right ascension 22h 09m 13.61893s[1]
Declination +33° 10′ 20.4778″[1]
Apparent magnitude (V) +5.58[2]
Characteristics
Spectral type G8IIIb[3]
B−V color index +0.985±0.003[2]
Astrometry
Radial velocity (Rv)+5.1±0.9[4] km/s
Proper motion (μ) RA: −48.117[1] mas/yr
Dec.: −73.408[1] mas/yr
Parallax (π)10.2111 ± 0.1137 mas[1]
Distance319 ± 4 ly
(98 ± 1 pc)
Absolute magnitude (MV)0.84[5]
Details
Mass2.48[6] M☉
Radius11.00+0.51
−0.83[1] R☉
Luminosity62.8±0.8[1] L☉
Surface gravity (log g)2.7[7] cgs
Temperature4,898+196
−110[1] K
Metallicity [Fe/H]−0.22[5] dex
Rotational velocity (v sin i)135[7] km/s
Age530[6] Myr
Other designations
π Peg, 27 Pegasi, BD+32°4349, HD 210459, HIP 109352, HR 8449, SAO 72064[8]
Database references
SIMBADdata

Pi1 Pegasi, Latinized from π1 Pegasi, is a star in the constellation Pegasus. Based upon changes to the proper motion of the visible component, this is a probable astrometric binary.[9] It has a yellow hue and is dimply visible to the naked eye with a combined apparent visual magnitude of +5.58.[2] The system is located approximately 319 light years distant from the Sun based on parallax,[1] and is drifting further away with a radial velocity of +5 km/s.[4] It is a member of the Ursa Major Moving Group of co-moving stars.[10]

π1 Pegasi (right) and π2 Pegasi (left) in optical light

The visible component is an aging giant star with a stellar classification of G8IIIb.[3] It has a high rate of spin, with a projected rotational velocity of 135 km/s.[7] This is giving it an equatorial bulge that is 17% larger than the polar radius.[11] It is a shell star, being orbited by a circumstellar shell of cooler gas.[12][13] This star is 530[6] million years old with 2.5[6] times the mass of the Sun. With the supply of hydrogen exhausted at its core, the star has cooled and expanded to 11[1] times the Sun's radius. It is radiating 63[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,898 K.[1]

  1. ^ a b c d e f g h i j k l Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference abt1985 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Takeda2008 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference luck2015 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference Massarotti2008 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Schmitt1990 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference vanBelle2012 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Hauck2000 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Slettebak1986 was invoked but never defined (see the help page).