Mu2 Scorpii


Mu2 Scorpii, also named Pipirima, is a star in the zodiac constellation of Scorpius. It has an apparent visual magnitude of +3.56, which is bright enough to be seen with the naked eye. Its distance from the Sun is about 474 light-years, as determined by parallax measurements. It is a member of the Upper Centaurus–Lupus subgroup of the Scorpius–Centaurus association. A super-Jupiter or brown dwarf is known to orbit it, and another is suspected.

Nomenclature

μ2 Scorpii is the star's Bayer designation.
A traditional Polynesian story is told of a brother and sister who flee their parents into the sky and become stars. In one account, the children become Shaula and Lesath in the tip of the tail of Scorpius, and in another they become Mu2 and Mu1 Scorpii. In the Tahitian version of this story, the brother and sister are named Pipiri and Rehua, and their parents call them Pipiri ma while chasing them into the sky: ma "with, and" is used after names to mean "et al.".
In 2016, the IAU organized a Working Group on Star Names to catalog and standardize proper names for stars. The WGSN approved the name Pipirima for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.
In Chinese astronomy, Mu2 Scorpii is identified as the second added star of the Tail asterism. It was historically called Shengong, a name which was later applied to the star cluster NGC 6231, and has been adopted by the IAU Working Group on Star Names for the star HD 153072.

Properties

Mu2 Scorpii is a blue-white B-type subgiant star with a stellar classification of B2 IV. It has an estimated diameter of 5.6 solar radii and a mass of 9.1 times the Sun's mass, and shines with 2,385 times the Sun's luminosity. The large mass of this star makes it a supernova progenitor. The outer atmosphere has an effective temperature of. It is some 20 million years old and is spinning with a projected rotational velocity of 58 km/s.

Planetary system

Two sub-stellar objects slightly above the deuterium burning limit were found in 2022 by direct imaging around Mu2 Scorpii. The outer one, designated μ2 Scorpii b, is definitely an orbiting planet or brown dwarf, and the inner one is a planetary candidate.