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Pi1 Ursae Majoris

Pi<sup>1</sup> Ursae Majoris (Pi<sup>1</sup>&nbsp;UMa, π<sup>1</sup>&nbsp;Ursae Majoris, π<sup>1</sup>&nbsp;UMa) is a yellow G-type main sequence dwarf with a mean apparent magnitude of +5.63. It is approximately 47.1 light years from Earth, and is a relatively young star with an age of about 200 million years. 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. 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.

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&nbsp;AU, consisting of 0.25&nbsp;μm grains of amorphous silicates or crystalline forsterite. There may also be a wider ring of larger (10&nbsp;μm) grains out to a distance of 16&nbsp;AU.

Naming and etymology

With π<sup>2</sup>, σ<sup>1</sup>, σ<sup>2</sup>, ρ, A and d, it composed the Arabic asterism Al Ṭhibā᾽, the Gazelle. 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 (π<sup>1</sup>) as Althiba II, π<sup>2</sup> as Althiba III, ρ as Althiba IV, σ<sup>1</sup> as Althiba V, σ<sup>2</sup> as Althiba VI, and d as Althiba VII.

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