Pi¹ Ursae Majoris (Pi¹ UMa, π¹ Ursae Majoris, π¹ UMa) is a yellow G-type main sequence dwarf with a mean

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of +5.63. It is approximately 46.8

light years A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astro ...

from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

, and is a relatively young star with an age of about 200 million years. It is classified as a BY Draconis type

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

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 The Ursa Major Moving Group, also known as Collinder 285 and the Ursa Major association, is the closest Stellar kinematics#Moving groups, stellar moving group – a set of stars with common velocities in space and thought to have a common orig ...

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 A debris disk (American English), or debris disc ( Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris ...

. 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.

Naming and etymology

With π², σ¹, σ², 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 (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''.

References

External links

TPF-C data for Hip 42438

{{DEFAULTSORT:Pi Ursae Majoris Ursae Majoris, Pi Ursae Majoris, 03 072905 G-type main-sequence stars Ursae Majoris, 03 BY Draconis variables Althiba II Circumstellar disks Ursa Major 042438 3391 BD+65 0643 Ursa Major moving group 0311