The Carina–Sagittarius Arm (also known as Sagittarius Arm or Sagittarius–Carina Arm, labeled -I) is generally thought to be a minor spiral arm of our home galaxy

Galaxy

A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

, the Milky Way

Milky Way

The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

. Each spiral arm is a long, diffuse curving streamer of 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...

s that radiates out from the galactic center

Galactic Center

The Galactic Center is the rotational center of the Milky Way galaxy. It is located at a distance of 8.33±0.35 kpc from the Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest...

. These gigantic structures are often composed of billions of stars and thousands of gas clouds. The Carina–Sagittarius Arm is one of the most pronounced arms in our galaxy as a large number of HII regions, young stars and giant molecular clouds are concentrated in it.

The Milky Way is a barred spiral galaxy

Barred spiral galaxy

A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in approximately two-thirds of all spiral galaxies...

, consisting of a central crossbar from which two major and several minor spiral arms radiate outwards.