Eta Sagittarii is a star system

Star system

A star system or stellar system is a small number of stars which orbit each other, bound by gravitational attraction. A large number of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems.-Binary star systems:A stellar...

 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....

 Sagittarius

Sagittarius (constellation)

Sagittarius is a constellation of the zodiac, the one containing the galactic center. Its name is Latin for the archer, and its symbol is , a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow...

, 149 light years

Light Years

Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....

 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...

.

It was formerly known as "Beta Telescopii" (β Tel). The SkyMap site has the name "Sephdar" attributed to η Sgr, but the etymology of this name is not clear.

The primary component, η Sagittarii A, is a spectral type M3.5 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...

. It is a 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...

 with small 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...

 fluctuations between +3.08 and 3.12, and is classified as 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:...

.

The brightest companion, η Sagittarii B, is spectral class F dwarf star, with an apparent 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...

 of +7.77. It is at a distance of 165 astronomical units from the primary and takes approximately 1 300 years to make one 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...

. The two stars are separated by 3.6 arcseconds on the sky.

Farther out are two dimmer members of the system, the 13th magnitude η Sagittarii C, separated from A by 33 arcseconds, and the 10th magnitude η Sagittarii D, 93 arcseconds from A.

This star will be in constellation Corona Australis

Corona Australis

Corona Australis or Corona Austrina is a constellation. Its name means "southern crown", and it contrasts with Corona Borealis, the northern crown...

around 6300 AD.