Theta Boötis

Star in the northern constellation of Boötes From Wikipedia, the free encyclopedia

Theta Boötis

Theta Boötis, Latinized from θ Boötis, is a star in the northern constellation of Boötes the herdsman, forming a corner of the upraised left hand of this asterism.[13] It has the traditional name Asellus Primus (/əˈsɛləs ˈprməs/; Latin for "first donkey colt")[13] and the Flamsteed designation 23 Boötis. Faintly visible to the naked eye, this star has a yellow-white hue with an apparent visual magnitude of 4.05.[2] It is located at a distance of 47.2 light years from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −10.6 km/s.[5]

Quick Facts Observation data Epoch J2000 Equinox J2000, Constellation ...
Theta Boötis
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Location of θ Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 25m 11.79695s[1]
Declination +51° 51 02.6772[1]
Apparent magnitude (V) 4.05[2] + 13.23[3]
Characteristics
Spectral type F7 V[2] + M2.5V[3]
U−B color index −0.02[4]
B−V color index +0.50[2]
Astrometry
Radial velocity (Rv)−10.627±0.0065[5] km/s
Proper motion (μ) RA: −235.97 mas/yr[1]
Dec.: −399.696 mas/yr[1]
Parallax (π)69.0686±0.1579 mas[1]
Distance47.2 ± 0.1 ly
(14.48 ± 0.03 pc)
Absolute magnitude (MV)3.25[6]
Details
A
Mass1.232±0.012[7] M
Radius1.726±0.012[7] R
Luminosity4.205±0.020[7] L
Surface gravity (log g)4.06±0.02[7] cgs
Temperature6,292±20[7] K
Metallicity [Fe/H]0.03[8] dex
Rotational velocity (v sin i)29.2[9] km/s
Age3.1 Gyr[10]
3.83[8] Gyr
B
Mass0.4–0.48[11] M
Radius0.4013±0.012[11] R
Luminosity0.022[11] L
Surface gravity (log g)4.91[11] cgs
Temperature3,521[11] K
Metallicity [Fe/H]−0.07[11] dex
Other designations
Asellus Primus, θ Boo, 23 Boötis, NSV 6669, BD+52°1804, FK5 531, GJ 549, HD 126660, HIP 70497, HR 5404, SAO 29137, WDS J14252+5151A, LTT 14245[12]
Database references
SIMBADdata
ARICNSdata
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Properties

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θ Boötis in optical light

The stellar classification of Theta Boötis is F7 V,[2] matching an F-type main-sequence star. It is a solar-type star that may be near the end of its main sequence lifetime based on a high luminosity for a star of its type.[10] Theta Boötis is a suspected variable star[14] and a source of X-ray emission.[15] There is evidence for low amplitude radial velocity variation of about 5 km/s.[10] The star has a 23% greater mass and a 73% larger radius than the Sun.[7] It is about 3–4 billion years old and is spinning with a projected rotational velocity of 29 km/s.[9] The star is radiating 4.2 times the luminosity of the Sun[16] from its photosphere at an effective temperature of 6,290 K.[7]

There is a nearby 11th magnitude optical companion star about 70 arcseconds away. This is a class M2.5 red dwarf that is separated by a minimum of 1,000 AUs. It is uncertain whether they are gravitationally bound, but they do have a common motion through space and so the two stars probably share a common origin.[17][3]

Nomenclature

θ Boötis, along with the other Aselli (ι Boo and κ Boo) and λ Boo, were Aulād al Dhiʼbah (أولاد الضّباع - awlād al-ḍibā‘), "the Whelps of the Hyenas".[13]

In Chinese, 天枪 (Tiān Qiāng), meaning Celestial Spear, refers to an asterism consisting of θ Boötis, κ2 Boötis and ι Boötis.[18] Consequently, the Chinese name for θ Boötis itself is 天枪三 (Tiān Qiāng sān, English: the Third Star of Celestial Spear.)[19]

References

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