The Norma Arm is a minor

spiral arm Spiral arms are a defining feature of spiral galaxies. They manifest as spiral-shaped regions of enhanced brightness within the galactic disc. Typically, spiral galaxies exhibit two or more spiral arms. The collective configuration of these arms i ...

of the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

extending from and around its central hub region. The inner portion of the Arm is called the ''Norma Arm'' in narrow meaning. The outer end of it is identified either with the Cygnus Arm (not to be confused with local and minor

Orion-Cygnus Arm The Orion Arm, also known as the Orion–Cygnus Arm, is a minor spiral arm within the Milky Way Galaxy spanning in width and extending roughly in length. This galactic structure encompasses the Solar System, including Earth. It is sometimes re ...

), which lies outside the

Perseus Arm The Perseus Arm is one of two major spiral arms of the Milky Way galaxy. The second major arm is called the Scutum–Centaurus Arm. The Perseus Arm begins from the distal end of the long Milky Way central bar. Previously thought to be 13,000 ligh ...

, or the Outer Arm, which is located farther away from the center of the Galaxy than the Cygnus Arm. The Norma Arm begins from the

Galactic Center The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a ...

, and extends outward to a radius of . It is named for the

Norma Norma may refer to: * Norma (given name), a given name (including a list of people with the name) ** Norma Lizbeth Ramos, a Mexican bullying victim Astronomy *Norma (constellation) * 555 Norma, a minor asteroid * Cygnus Arm or Norma Arm, a spiral ...

constellation, through which the Arm as seen from Earth passes. Like many other galaxies of similar type, the Milky Way consists of a large mass of

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

s shaped into the form of a relatively flat disc by

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

. The disc is rotating, with the dense central body of stars moving at greater speeds than those toward the rim of the disc. As a result, the pattern of stars within the Galaxy as viewed from directly above or below the disc has formed into a spiral. Because of localised gravitational variations, the spiral pattern has itself formed several distinct 'spiral arms', where particularly large numbers of stars can be found.

References

{{Portal bar, Stars, Outer space Milky Way arms Galactic astronomy Spiral galaxies

See also

References