Eta Ophiuchi, also known as η Oph or η Ophiuchi, 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....

 Ophiuchus

Ophiuchus

Ophiuchus is a large constellation located around the celestial equator. Its name is from the Greek "serpent-bearer", and it is commonly represented as a man grasping the snake that is represented by the constellation Serpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century...

. It also has the traditional name Sabik.

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...

, this star is considered part of , meaning Left Wall of Heavenly Market Enclosure

Heavenly Market enclosure

Tian Shi Yuan, the Heavenly Market Enclosure , is one of the San Yuan or Three enclosures. Stars and constellations of this group are visible during late summer and early autumn in the Northern Hemisphere . The summer triangle lies directly to the northwest.-Asterisms:The asterisms are :...

, which refers to an asterism

Asterism (astronomy)

In astronomy, an asterism is a pattern of stars recognized on Earth's night sky. It may form part of an official constellation, or be composed of stars from more than one. Like constellations, asterisms are in most cases composed of stars which, while they are visible in the same general direction,...

 (pattern of stars) representing eleven old states in China that mark the left borderline of the enclosure, consisting of η Ophiuchi, δ Herculis

Delta Herculis

Delta Herculis is a fourth-magnitude star in the constellation Hercules. It has the traditional name Sarin....

, λ Herculis

Lambda Herculis

Lambda Herculis is a star inthe constellation Hercules.It has the traditional name Maasym .In Chinese, , meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states in China which is marking the left borderline of the enclosure, consisting of λ...

, μ Herculis

Mu Herculis

Mu Herculis is a nearby star system about 27.1 light years from Earth in the constellation Hercules. Its main star, Mu Herculis A is fairly similar to the Sun although more highly evolved with a...

, ο Herculis

Omicron Herculis

Omicron Herculis is a multiple star system in the constellation Hercules. It has the traditional name Atia and the Flamsteed designation 103 Herculis.- Properties :...

, 112 Herculis, ζ Aquilae

Zeta Aquilae

Zeta Aquilae is a triple star system in the constellation Aquila. It has the traditional names Deneb el Okab, from an Arabic term ذنب العقاب ðanab al-cuqāb meaning "the tail of the falcon", and the Mandarin names Woo and Yuë, derived from and represent the state Wu , an old state was located at...

, θ¹ Serpentis, η Serpentis

Eta Serpentis

Eta Serpentis is a binary star in the constellation Serpens. The primary, Eta Serpentis A, is an orange K-type giant with an apparent magnitude of +3.23. It has a distant 12th magnitude companion, Eta Serpentis B, 3 arcminutes away...

, ν Ophiuchi

Nu Ophiuchi

Nu Ophiuchi is a Class K0, third-magnitude star in the constellation Ophiuchus. Its closest stellar neighbour is the bright binary system Tau Ophiuchi, roughly 16.9 light years away from the star...

 and ξ Serpentis

Xi Serpentis

Xi Serpentis is a triple star system in the constellation Serpens. The primary star, Xi Serpentis A, is a yellow-white F-type giant with an apparent magnitude of +3.54. It is a spectroscopic binary with an orbital period of 2.29 days. A 13th magnitude companion, Xi Serpentis B, is located 25...

. Consequently, η Ophiuchi itself is known as , representing the state Song

Song (state)

Sòng was a state during the Eastern Zhou Spring and Autumn Period . Its capital was Shangqiu . In 701 BC, a political marriage between Lady Yong of Song and Duke Zhuang of Zheng empowered Song to manipulate the management of Zheng.- Origin :After King Wu of Zhou overthrew King Zhou of Shang,...

(宋).

Properties

η Oph is actually a binary

Binary system (astronomy)

A binary system is an astronomical term referring to two objects in space which are so close that their gravitational interaction causes them to orbit about a common center of mass. Some definitions A binary system is an astronomical term referring to two objects in space (usually stars, but also...

 star system that is difficult to resolve in amateur telescopes but whose true nature has been determined through use of more advanced techniques. The "primary" star (whose observational data make up the table in this article), which could nominally be referred to as η Oph A, is actually only slightly larger and warmer than its companion, η Oph B. Individually each star is a fairly unremarkable A class main sequence

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...

 star, but as a binary pair

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...

 they are unusual. Each star orbits around a common center in a very fast and highly elliptical orbit

Orbit

In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

, making planetary formation

Planet

A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

 impossible in this system and some stellar data imprecise.

η Oph is the northern pole star of the planet Uranus

Uranus

Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

.

Namesakes

USS Sabik (AK-121)

USS Sabik (AK-121)

USS Sabik was a commissioned by the U.S. Navy for service in World War II. She was responsible for delivering troops, goods and equipment to locations in the war zone....

 was a United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 Crater class cargo ship

Crater class cargo ship

Crater-class cargo ship is a category of freighter that was constructed for use by the United States Navy during World War II under Maritime Commission EC2-S-C1 type....

named after the star.