The Scutum–Centaurus Arm is one of the Milky Way’s two major spiral arms, a dense band of old and young stars springing from the far end of the bar.
At a glance
| runs from the centre | 4.4 to 15 kpcmodel |
|---|---|
| width | about 1,400 light-yearsmodel |
| pitch angle | 14.1°model |
Read off the piece’s own catalogue, the same values it draws with. Model marks a property of the piece’s galaxy model rather than a measurement.
About Scutum–Centaurus Arm
The arm is named after the two constellations in which our view runs tangent to it: Scutum in the northern half of the sky and Centaurus in the southern. It leaves the end of the central bar and winds outward, passing between the Sun and the Galactic Centre on the far side of the Sagittarius–Carina Arm.
Infrared surveys that counted old stars across the inner Galaxy found a strong excess along this arm and along the Perseus Arm, and much less along the others. That is why the Milky Way is often described as having two major arms carrying both stars and gas, and several minor arms made mostly of gas and young clusters.
Radio astronomers have also found a faint arm of gas at the very edge of the disc, on the far side of the Galaxy, that may be the outer continuation of the Scutum–Centaurus Arm.
What you see in the piece
Seen from the Sun the arm lies behind thick dust and barely shows in visible light; switch the band row to infrared or radio and its glow comes through, or rise out of the disc to see its sweep.
Measured or modelled
The arm’s placement, width and pitch angle follow the maser fits of Reid and collaborators. The link between the inner arm and the distant outer arc of gas is an interpretation, not a measurement.
Questions
Is the Scutum–Centaurus Arm a major arm of the Milky Way?
Yes. Infrared star counts show it carries a large share of the Galaxy’s old stars, together with the Perseus Arm. In the piece’s model it runs from 4.4 to 15 kpc from the centre.
How wide is the Scutum–Centaurus Arm?
The piece models it as about 1,400 light-years wide, with a pitch angle of 14.1°.