  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 52m 20.14532s[1] |
| Declination | −38° 01′ 03.1258″[1] |
| Apparent magnitude (V) | +3.56[2] |
| Characteristics | |
| Evolutionary stage | subgiant[3] |
| Spectral type | B2 IV[4] |
| U−Bcolor index | −0.878[2] |
| B−Vcolor index | −0.219[2] |
| Astrometry | |
| Radial velocity (Rv) | +1.4[5] km/s |
| Proper motion (μ) | RA: −11.09[1]mas/yr Dec.: −23.32[1]mas/yr |
| Parallax (π) | 6.88±0.12 mas[1] |
| Distance | 474 ± 8 ly (145 ± 3 pc) |
| Absolute magnitude (MV) | −2.25[6] |
| Details[3] | |
| Mass | 9.1±0.3 M☉ |
| Radius | 5.6±0.2 R☉ |
| Luminosity | 2,385[7] L☉ |
| Surface gravity (log g) | 3.8±0.2 cgs |
| Temperature | 21,700±900 K |
| Rotational velocity (v sin i) | 58[8] km/s |
| Age | 20±4 Myr |
| Other designations | |
| Pipirima,μ2 Sco,CD−37°11037,HD 151985,HIP 82545,HR 6252,SAO 208116[9] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Mu2 Scorpii, also namedPipirima/pɪˈpɪrɪmə/,[10] is astar in thezodiacconstellation ofScorpius. It has anapparent visual magnitude of +3.56,[2] which is bright enough to be seen with the naked eye. Its distance from theSun is about 474 light-years, as determined byparallax measurements.[1] It is a member of the Upper Centaurus–Lupus subgroup of theScorpius–Centaurus association.[11] Asuper-Jupiter orbrown dwarf is known to orbit it, and another is suspected.[3]
μ2 Scorpii (Latinised toMu2 Scorpii, abbreviatedμ2 Sco,Mu2 Sco) is the star'sBayer designation.
A traditionalPolynesian story is told of a brother and sister who flee their parents into the sky and become stars. In one account, the children becomeShaula andLesath in the tip of the tail of Scorpius,[12] and in another they become Mu2 andMu1 Scorpii.[13][14] In theTahitian version of this story, the brother and sister are namedPipiri andRehua, and their parents call themPipiri ma while chasing them into the sky:ma "with, and" is used after names to mean "et al."[12][15] (In a similar version of the story told in theCook Islands, they becomeOmega1 and Omega2 Scorpii).[12]
In 2016, the IAU organized aWorking Group on Star Names (WGSN)[16] to catalog and standardize proper names for stars. The WGSN approved the namePipirima for this star on 5 September 2017 (along withXamidimura for its partner) and it is now so included in the List of IAU-approved Star Names.[10]
InChinese astronomy, Mu2 Scorpii is identified as the second added star of theTail asterism (Chinese:尾宿增二;pinyin:Wěi Xiù zēng èr).[18] It was historically called Shengong (Chinese:神宮;pinyin:Shéngōng),[19] a name which was later applied to the star clusterNGC 6231, and has been adopted by theIAU Working Group on Star Names for the starHD 153072.[20]
Mu2 Scorpii is a blue-whiteB-typesubgiant star with astellar classification of B2 IV.[4] It has an estimated diameter of 5.6solar radii and a mass of 9.1 times theSun's mass,[3] and shines with 2,385 times theSun's luminosity.[7] The large mass of this star makes it asupernova progenitor. Theouter atmosphere has aneffective temperature of21,700 K. It is some 20 million years old[3] and is spinning with aprojected rotational velocity of 58 km/s.[8]
Two sub-stellar objects slightly above thedeuterium 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.[3]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (years) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| c(unconfirmed) | 18.5±1.5MJ | 18.9+11.7 −5.0 | — | 0.61+0.19 −0.32 | 62.8+9.9 −16.6° | — |
| b | 14.4±0.8 MJ | 242.4+114.5 −52.1 | — | 0.56+0.27 −0.26 | 96.6+21.5 −20.5° | — |
