Mu Geminorum is a star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 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....

 Gemini

Gemini (constellation)

Gemini is one of the constellations of the zodiac. It was one of the 48 constellations described by the 2nd century astronomer Ptolemy and it remains one of the 88 modern constellations today. Its name is Latin for "twins", and it is associated with the twins Castor and Pollux in Greek mythology...

, approximately 230 light years away from Earth. It has the traditional name Tejat Posterior, which means back foot, because it is the foot of Castor, one of the Gemini twins. The names Calx (Latin, meaning heel), Nuhatai (from Arabic

Arabic language

Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 Al Nuḥātai, the dual form of Al Nuḥāt, "a Camel's Hump". This is the name of star association consisting this star, along with γ Gem

Gamma Geminorum

Gamma Geminorum is the second brightest star in the constellation Gemini. It has the traditional names Alhena and Almeisan....

 - Alhena, ν Gem, η Gem

Eta Geminorum

Eta Geminorum is a triple star system in the constellation Gemini. It has the traditional names Tejat Prior, Propus and Praepes and Pish Pai ....

 - Tejat Prior and ξ Gem

Xi Geminorum

Xi Geminorum is a star in the constellation Gemini. It has the traditional name Alzirr, meaning "the button" in Arabic.This star, along with γ Gem , μ Gem , ν Gem and η Gem were Al Han'ah, "the brand"...

 - Alzirr) and Pish Pai (from the Persian

Persian language

Persian is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran, Afghanistan, Tajikistan and countries which historically came under Persian influence...

 Pīshpāy, پیش‌پای, meaning foreleg) have also been applied to this star.

In Chinese

Chinese language

The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...

, , meaning Well

Well (Chinese constellation)

The Well mansion is one of the Twenty-eight mansions of the Chinese constellations. It is one of the southern mansions of the Vermilion Bird.-Asterisms:...

 (asterism), refers to an asterism consisting of μ Geminorum, γ Geminorum

Gamma Geminorum

Gamma Geminorum is the second brightest star in the constellation Gemini. It has the traditional names Alhena and Almeisan....

, ν Geminorum, ξ Geminorum

Xi Geminorum

Xi Geminorum is a star in the constellation Gemini. It has the traditional name Alzirr, meaning "the button" in Arabic.This star, along with γ Gem , μ Gem , ν Gem and η Gem were Al Han'ah, "the brand"...

, ε Geminorum

Epsilon Geminorum

Epsilon Geminorum is a star in the constellation of Gemini. It has the traditional name Mebsuta ....

, 36 Geminorum, ζ Geminorum

Zeta Geminorum

Zeta Geminorum is a star in the constellation Gemini. It has the traditional name Mekbuda.The name Mekbuda has roots in ancient Arabic where it and the star Mebsuta were the paws of a lion...

 and λ Geminorum

Lambda Geminorum

Lambda Geminorum is a Class A3, fourth-magnitude star in the constellation Gemini. Lambda Geminorum is a variable star located about 95 light-years from Earth....

. Consequently, μ Geminorum itself is known as

Properties

Mu Geminorum is an irregular variable

Irregular variable

An irregular variable is a type of variable star in which variations in brightness show no regular periodicity. There are two main sub-types of irregular variable: eruptive and pulsating.Eruptive irregular variables are divided into three categories:...

 of type LB. Its brightness varies between magnitude

Apparent magnitude

The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 +2.75 and +3.02 over a 72 day period, with a 2,000 day period of long term variation. It is a red giant

Red giant

A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...

 of the spectral class

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...

 M3, with a surface temperature of 3,650 kelvin

Kelvin

The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...

s, meaning it is brighter, yet cooler than our Sun.