Why is the disk of the Milky Way Blue and the bulge red?

Why does the galactic bulge appear red?

These bulges are composed primarily of stars that are older, Population II stars, and hence have a reddish hue (see stellar evolution). These stars are also in orbits that are essentially random compared to the plane of the galaxy, giving the bulge a distinct spherical form.

Why are galactic discs blue?

Typically the stars in a galaxy bulge have reddish colors, while the disks tend to be more blue. … The disks appear bluer because they are the site of ongoing star formation. Massive stars are very bright and very hot, which gives their light a blue color, but they also have very short lifetimes by stellar standards.

Why are the colors of the bulge and the colors of the spiral arms so different?

3. Look at the spiral galaxies. … This observation suggests that the stars that are contained in each region are different: The spiral arms look blue because they contain many young stars (and young, massive stars are blue), while the bulges look yellowish because they are rich in evolved stars (that look more reddish).

Whats the difference between the Galactic bulge and Galactic disk?

Unlike the disk, the distribution of stars in the galactic bulge is not exponential. It was once thought to be spheroidal, with an effective radius – the radius which contains half the light – of a few kpc. … Bulge or bar, the mass of the inner structure is about 1010 Msun , or about 1/6 that of the disk.

Why are the spiral arms blue but the bulge red?

The blue image actually represents the galaxy as seen in ultraviolet light, where we see the hot massive stars in the spiral arms. The red image is dominated by the light from red giant stars, many of which have lived long enough to migrate out of the spiral arms where they were formed.

What is the galactic bulge in the Milky Way?

In the center of the galaxy is the bar-shaped galactic bulge which harbors a supermassive black hole with a mass equal to that of about 3 million suns. Surrounding the central bulge is a relatively thin disk of stars about two thousand light years thick and roughly 100,000 light years across.

Why is the Milky Way a disc?

Gas clouds produce stars, and so most stars will also be in the plane of the disc. Very old clusters of stars in globular clusters however can be found in a spherical pattern around the disc. So galaxies form disc shapes because the gas that makes stars falls into a disc shape.

What color are disk stars?

The arms are embedded in a thin disk of stars. Both the arms and the disk of a spiral system are blue in color, whereas its central areas are red like an elliptical galaxy. Notice in the above picture of M100 from HST, that the center of the spiral is red/yellow and the arms are blue.