Pi1 Ursae Majoris

For other stars with this name, see Pi Ursae Majoris and Muscida.

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.^[14] 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]

Pi¹ Ursae Majoris

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
Characteristics
Spectral type	G1.5Vb[2]
U−B color index	+0.07[3]
B−V color index	+0.62[3]
Variable type	BY Draconis
Astrometry
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 mas[1]
Distance	46.8 ± 0.2 ly (14.36 ± 0.08 pc)
Absolute magnitude (MV)	4.86[5]
Details
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
SIMBAD	data

A light curve for pi¹ Ursae Majoris, plotted from TESS data.^[12] The main plot shows the variation over several weeks, and the inset plot shows the same data folded, assuming a 4.9 day period,^[13] and averaged into 250 phase bins.

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.^[15]

Naming and etymology

With π², σ¹, σ², ρ, A and d, it composed the Arabic asterism Al Ṭhibā᾽, the Gazelle.^[16] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Ṭhibā were the title for seven stars : A as Althiba I, this star (π¹) as Althiba II, π² as Althiba III, ρ as Althiba IV, σ¹ as Althiba V, σ² as Althiba VI, and d as Althiba VII.^[17]

References

1. van Leeuwen, Floor (2007). "Hipparcos, the new Reduction of the Raw data". Astron. Astrophys. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. 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, arXiv:astro-ph/0106537, Bibcode:2001MNRAS.328...45M, doi:10.1046/j.1365-8711.2001.04781.x, S2CID 55727428
3. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
4. 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, arXiv:0706.0542, Bibcode:2007AJ....133.2524W, doi:10.1086/514336, S2CID 122854
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, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
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, arXiv:1007.0425, Bibcode:2011ApJS..192....2S, doi:10.1088/0067-0049/192/1/2, S2CID 119226823
7. 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, CiteSeerX 10.1.1.43.4478, doi:10.1086/301488, S2CID 16930014
8. 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, arXiv:astro-ph/0611618, Bibcode:2007MNRAS.374..664C, doi:10.1111/j.1365-2966.2006.11196.x, S2CID 119428437
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, arXiv:astro-ph/0308429, Bibcode:2003A&A...411..559K, doi:10.1051/0004-6361:20031378, S2CID 18478960
10. 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, arXiv:1007.1132, Bibcode:2010A&A...521A..12M, doi:10.1051/0004-6361/201014948, S2CID 119209183
11. 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, arXiv:0807.1686, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785, S2CID 27151456
12. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
13. Kochukhov, O.; Hackman, T.; Lehtinen, J. J. (March 2020). "Hidden magnetic fields of young suns" (PDF). Astronomy & Astrophysics. 635: A142. arXiv:2002.10469. Bibcode:2020A&A...635A.142K. doi:10.1051/0004-6361/201937185. S2CID 211296645. Retrieved 30 June 2022.
14. 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
15. 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, arXiv:astro-ph/0601467, Bibcode:2006ApJ...639.1166B, doi:10.1086/499424, S2CID 13493797
16. Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 444
17. Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology.

External links

• TPF-C data for Hip 42438^{[permanent dead link‍]}
• Individual results for HD 72905