  | |
| 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 | |
| Spectral type | B2 IV[3] |
| U−Bcolor index | −0.878[2] |
| B−Vcolor index | −0.219[2] |
| Astrometry | |
| Radial velocity (Rv) | +1.4[4] 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[5] |
| Details[6] | |
| 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 Scorpii,CD−37° 11037,HD 151985,HIP 82545,HR 6252,SAO 208116.[9] | |
| Database references | |
| SIMBAD | data |
Mu2 Scorpii (μ2 Scorpii, abbreviatedMu2 Sco,μ2 Sco), 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.[6]
Mu2 Scorpii is a blue-whiteB-typesubgiant star with astellar classification of B2 IV.[3] It has an estimated diameter of 5.6solar radii and a mass of 9.1 times theSun's mass,[6] and shines with 2,385 times theSun's luminosity.[7] The large mass of this star make it asupernova progenitor. Theouter atmosphere has aneffective temperature of21,700 K. It is some 20 million years old[6] and is spinning with aprojected rotational velocity of 58 km/s.[8]
μ2 Scorpii (Latinised toMu2 Scorpii) is the star'sBayer designation.
In Tahiti, atraditional story is told of a brother and sister, namedPipiri andRehua, who flee their parents into the sky and become stars. Their parents call themPipiri ma while chasing them into the sky:ma "with, and" is used after names to mean "et al."[12][13] In one account, the children becomeShaula andLesath in the tip of the tail of Scorpio,[12] and in another they become Mu2 andMu1 Scorpii.[citation needed] (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)[14] 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 called 尾宿增二.[15]
Two sub-stellar objects slightly above deuterium burning limit (brown dwarfs) were found in 2022 by direct imaging near 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.[6]
| 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° | — |
{{cite web}}: CS1 maint: postscript (link)