Theta Aurigae (θ Aur, θ Aurigae) is a binary star

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

in the constellation

Constellation

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 Auriga

Auriga (constellation)

Auriga is a constellation in the northern sky. Its name is Latin for 'charioteer' and its stars form a shape that has been associated with the pointed helmet of a charioteer. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains among the 88 modern...

. It is approximately 173 light-years from Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. Rarely used proper names for this star include Bogardus and Mahasim, the latter from the Arabic المِعْصَم al-mi^cşam "wrist" (of the charioteer), which was also used for Eta Aurigae

Eta Aurigae

Eta Aurigae is a star in the constellation Auriga. Along with ζ Aurigae it represents one of the Kids of the she-goat Capella, from which it gets its Latin traditional name Hoedus II or Haedus II, from the Latin hædus "kid"; Zeta Aurigae is Hoedus I...

.

The primary, θ Aurigae A, is a white A-type

Stellar classification

In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 main sequence dwarf

Main sequence

The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...

 with an apparent magnitude of +2.7. Its companion, θ Aurigae B, is a yellow G-type

Stellar classification

In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 main sequence dwarf with an apparent magnitude of +7.2. The two stars are separated by 3.5 arcseconds. A third star, the 11th magnitude θ Aurigae C, is 49 arcseconds away, and is an optical companion

Double star

In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...

.

The mean combined apparent magnitude of the system is +2.65 but the primary is an Alpha2 Canum Venaticorum type

Alpha2 Canum Venaticorum variable

An Alpha2 Canum Venaticorum variable is a type of variable star. These stars are chemically peculiar main sequence stars of spectral class B8p to A7p. They have strong magnetic fields and strong silicon, strontium, or chromium spectral lines...

 variable star

Variable star

A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...

so the system's brightness varies from magnitude +2.62 to +2.70 with a period of 1.37 days.

It is known as 五車四 (the Fourth Star of the Five Chariots) in Chinese.