Alight curve for pi1 Ursae Majoris, plotted fromTESS data.[13] The main plot shows the variation over several weeks, and the inset plot shows the same data folded, assuming a 4.9 day period,[14] and averaged into 250 phase bins.
Pi1 Ursae Majoris (Pi1 UMa,π1 Ursae Majoris,π1 UMa) is a yellowG-typemain sequence dwarf with a meanapparent magnitude of +5.63. It is approximately 46.8light years fromEarth,[1] and is a relatively young star with an age of about 200 million years.[11] It is classified as aBY Draconis typevariable 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.[15] Based upon itsspace velocity components, this star is a member of theUrsa Major moving group of stars that share a common motion through space.[7][10]
Anexcess of infrared radiation has been detected from this system, which suggests the presence of adebris 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.[16]
Withπ2,σ1,σ2,ρ,A andd, it composed the ArabicasterismAl Ṭhibā᾽, the Gazelle.[17] According to the catalogue of stars in theTechnical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars,Al Ṭhibā were the title for seven stars :A asAlthiba I, this star (π1) asAlthiba II,π2 asAlthiba III,ρ asAlthiba IV,σ1 asAlthiba V,σ2 asAlthiba VI, andd asAlthiba VII.[18]
^abJohnson, 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
^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
