Theta Draconis, a name Latinized from θ Draconis, is a binary star system in the northern

circumpolar constellation A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest po ...

Draco Draco is the Latin word for serpent or dragon. Draco or Drako may also refer to: People * Draco (lawgiver) (from Greek: Δράκων; 7th century BC), the first lawgiver of ancient Athens, Greece, from whom the term ''draconian'' is derived * ...

. It is faintly visible to the naked eye at night with an

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...

of 4.12. Parallax measurements place it at an estimated distance of from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, and it is drifting closer with a radial velocity of −8 km/s. It has a relatively high proper motion, traversing the celestial sphere at the rate of per year. O. J. Eggen included this star as a member of the

NGC 1901 NGC 1901 is an open cluster in the Dorado Constellation. It has a bright middle and is a little rich, with stars from 7th magnitude downwards. The celestial object was discovered on 30 December 1836 by the British astronomer John Hers ...

supercluster based on its space motion. The binary nature of this system was discovered by W. W. Campbell in 1899, and the first set of orbital elements was published by H. D. Curtis in 1907. It is a single-lined spectroscopic binary in a close orbit with a

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

of 3.07 days and an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

(ovalness) of 0.04. The secondary component has been resolved in the

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

H band, allowing an estimation of the mass ratio as . Some velocity variation of K₁ was observed by M. Mayor and T. Mazeh in 1987, which is suggestive of a tertiary component to the system. The primary component is a solar-type star that at various times has been assigned stellar classifications of F9 V and F8IV-V. The star is about two billion years old and is spinning with a

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulg ...

of 31 km/s. It has a high metallicity (heavy element abundances) with around 20% more mass than the Sun and nearly three times the Sun's radius. The star displays no chromospheric emission and may be on or entering the subgiant stage. Because of the close orbit, it could be filling up to 60% of its

Roche lobe In astronomy, the Roche lobe is the region around a star in a binary system within which orbiting material is gravitationally bound to that star. It is an approximately teardrop-shaped region bounded by a critical gravitational equipotential ...

. The star is radiating ten times the luminosity of the Sun from its photosphere at an effective temperature of .

Chinese name

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of ...

, (), meaning '' Left Wall of Purple Forbidden Enclosure'', refers to an asterism consisting of θ Draconis, ι Draconis, η Draconis, ζ Draconis, υ Draconis,

73 Draconis 73 may refer to: * 73 (number) * one of the years 73 BC, AD 73, 1973, 2073 * ''73'' (magazine), a United States-based amateur radio magazine * 73 Best regards, a popular Morse code abbreviation * '' No. 73'', a British 1980s children's TV show *N ...

, γ Cephei and 23 Cassiopeiae. Consequently, the

Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are ofte ...

for θ Draconis itself is (, en, the Second Star of Left Wall of Purple Forbidden Enclosure.), representing (), meaning ''The First Premier''. 上宰 (Shǎngzǎi) is westernized into ''Shang Tsae'' by R.H. Allen with meaning "the Minor Steward" but it was for η Dra (Aldibain).

References

External links

* {{Sky, 16, 01, 53.35, +, 58, 33, 54.90, 1000000 F-type main-sequence stars Spectroscopic binaries Draco (constellation) Draconis, Theta Durchmusterung objects Draconis, 13 144284 078527 5986