Pi1 Ursae Majoris

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Pi1 Ursae Majoris
Diagram showing star positions and boundaries of the Centaurus constellation and its surroundings
Diagram showing star positions and boundaries of the Centaurus constellation and its surroundings

Location of π¹ Ursae Majoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 08h 39m 11.70440s[1]
Declination +65° 01′ 15.2667″[1]
Apparent magnitude (V) 5.63
Spectral type G1.5Vb[2]
U−B color index +0.07[3]
B−V color index +0.62[3]
Variable type BY Draconis
Radial velocity (Rv) –13.88 ± 0.47[4] km/s
Proper motion (μ) RA: -27.44 ± 0.31[1] mas/yr
Dec.: +88.13 ± 0.26[1] mas/yr
Parallax (π) 69.66 ± 0.37[1] mas
Distance 46.8 ± 0.2 ly
(14.36 ± 0.08 pc)
Absolute magnitude (MV) 4.86[5]
Mass 0.90[6] M
Luminosity 0.97[7] L
Surface gravity (log g) 4.48[8] cgs
Temperature 5,884 ± 6.8[9] K
Metallicity [Fe/H] –0.04[8] dex
Rotation 5 days[10]
Rotational velocity (v sin i) 14.27[4] km/s
Age 200[11] Myr
Other designations
π¹ Ursae Majoris, π¹ UMa, Pi1 UMa, 3 Ursae Majoris, BD +65°643, GC 11817, HD 72905, HIP 42438, HR 3391, PPM 16705, SAO 14609.
Database references

Pi1 Ursae Majoris (Pi1 UMa, π¹ Ursae Majoris, π¹ UMa) is a yellow G-type main sequence dwarf with a mean apparent magnitude of +5.63. It is approximately 46.8 light years from Earth,[1] and is a relatively young star with an age of about 200 million years.[11] It is classified as a BY Draconis type variable star and its brightness varies by 0.08 magnitudes. In 1986, it became the first solar-type star to have the emission from an X-ray flare observed.[12] Based upon its space velocity components, this star is a member of the Ursa Major moving group of stars that share a common motion through space.[7][10]

An excess of infrared radiation has been detected from this system, which suggests the presence of a debris disk. The best fit to the data indicates that there is a ring of fine debris out to a radius of about 0.4 AU, consisting of 0.25 μm grains of amorphous silicates or crystalline forsterite. There may also be a wider ring of larger (10 μm) grains out to a distance of 16 AU.[13]


  1. ^ a b c d e f van Leeuwen, Floor (2007). Hipparcos, the new Reduction of the Raw data. Astrophysics and Space Science Library. 350. Bibcode:2007A&A...474..653V. ISBN 978-1-4020-6341-1. arXiv:0708.1752Freely accessible. doi:10.1051/0004-6361:20078357.  Note: see VizieR catalogue I/311.
  2. ^ Montes, D.; et al. (November 2001), "Late-type members of young stellar kinematic groups - I. Single stars", Monthly Notices of the Royal Astronomical Society, 328 (1): 45–63, Bibcode:2001MNRAS.328...45M, arXiv:astro-ph/0106537Freely accessible, doi:10.1046/j.1365-8711.2001.04781.x 
  3. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J 
  4. ^ a b White, Russel J.; Gabor, Jared M.; Hillenbrand, Lynne A. (June 2007), "High-Dispersion Optical Spectra of Nearby Stars Younger Than the Sun", The Astronomical Journal, 133 (6): 2524–2536, Bibcode:2007AJ....133.2524W, arXiv:0706.0542Freely accessible, doi:10.1086/514336 
  5. ^ Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, Bibcode:2009A&A...501..941H, arXiv:0811.3982Freely accessible, doi:10.1051/0004-6361/200811191. 
  6. ^ Shaya, Ed J.; Olling, Rob P. (January 2011), "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue", The Astrophysical Journal Supplement, 192 (1): 2, Bibcode:2011ApJS..192....2S, arXiv:1007.0425Freely accessible, doi:10.1088/0067-0049/192/1/2 
  7. ^ a b Gaidos, E. J.; Henry, G. W.; Henry, S. M. (August 2000), "Spectroscopy and Photometry of Nearby Young Solar Analogs", The Astronomical Journal, 120 (2): 1006–1013, Bibcode:2000AJ....120.1006G, doi:10.1086/301488 
  8. ^ a b Cenarro, A. J.; et al. (January 2007), "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters", Monthly Notices of the Royal Astronomical Society, 374 (2): 664–690, Bibcode:2007MNRAS.374..664C, arXiv:astro-ph/0611618Freely accessible, doi:10.1111/j.1365-2966.2006.11196.x 
  9. ^ Kovtyukh, V. V.; et al. (2003), "High precision effective temperatures for 181 F-K dwarfs from line-depth ratios", Astronomy and Astrophysics, 411 (3): 559–564, Bibcode:2003A&A...411..559K, arXiv:astro-ph/0308429Freely accessible, doi:10.1051/0004-6361:20031378 
  10. ^ a b Maldonado, J.; et al. (October 2010), "A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups", Astronomy and Astrophysics, 521: A12, Bibcode:2010A&A...521A..12M, arXiv:1007.1132Freely accessible, doi:10.1051/0004-6361/201014948 
  11. ^ 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, Bibcode:2008ApJ...687.1264M, arXiv:0807.1686Freely accessible, doi:10.1086/591785 
  12. ^ Landini, M.; et al. (March 1986), "EXOSAT detection of an X-ray flare from the solar type star Pi-prime UMa", Astronomy and Astrophysics, 157 (2): 217–222, Bibcode:1986A&A...157..217L 
  13. ^ Beichman, C. A.; et al. (2006), "IRS Spectra of Solar-Type Stars: A Search for Asteroid Belt Analogs", The Astrophysical Journal, 639 (2): 1166–1176, Bibcode:2006ApJ...639.1166B, arXiv:astro-ph/0601467Freely accessible, doi:10.1086/499424 

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