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Iota Boötis

ι Boötis
Boötes constellation map.svg
Red circle.svg

Location of ι Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 16m 09.92995s
Declination +51° 22′ 02.0267″
Apparent magnitude (V) 4.75(4.73 - 4.78)
Characteristics
Spectral type A7 V
U−B color index +0.06
B−V color index +0.20
R−I color index +0.09
Variable type Delta Scuti variable
Astrometry
Radial velocity (Rv) −18.7 km/s
Proper motion (μ) RA: -149.39 mas/yr
Dec.: +88.72 mas/yr
Parallax (π) 34.40 ± 0.19mas
Distance 94.8 ± 0.5 ly
(29.1 ± 0.2 pc)
Absolute magnitude (MV) +2.38
Details
Mass 1.81 M
Radius 1.6 R
Luminosity 9.6 L
Surface gravity (log g) 4.3 cgs
Temperature 8,000 K
Metallicity [Fe/H] +0.19 dex
Rotational velocity (v sin i) 144 km/s
Other designations
Asellus Secondus,21 Boötis, BD+52°1784, FK5 528, HD 125161, HIP 69713, HR 5350, SAO 29071, Wo 9474, WDS J14162+5122
Database references
SIMBAD data
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

Iota Boötis (ι Boo, ι Boötis) is a star system in the constellation Boötes. It has the traditional name Asellus Secundus (Latin for "second donkey colt") and the Flamsteed designation 21 Boötis. It is approximately 95 light years from Earth.

This star, along with the other Aselli (θ Boo and κ Boo) and λ Boo, were Aulād al Dhiʼbah (أولاد الضّباع - aulād al dhiʼb), "the Whelps of the Hyenas".

In Chinese, 梗河 (Tiān Qiāng), meaning Celestial Spear, refers to an asterism consisting of ι Boötis, κ2 Boötis and θ Boötis. Consequently, ι Boötis itself is known as 天槍二 (Tiān Qiāng èr, English: the Second Star of Celestial Spear.)

Iota Boötis has a companion at an angular distance of 38.6 arcseconds, easily separated with binoculars.

The primary component, Iota Boötis, is a white A-type main sequence dwarf with a mean apparent magnitude of +4.75. It is classified as a Delta Scuti type variable star and its brightness varies from magnitude +4.73 to +4.78 with a stable period of 38 minutes.

The companion, HD 234121, is a magnitude +8.27 main sequence star belonging to spectral class K0. It is separated from ι Boo by 1,100 AU.


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