Where does the spiral arms lie?
All spiral arms lie within the thin disk of the galaxy. They are delineated by dark dust lanes and highlighted by young, blue stars and luminous nebulae.
What triggers star formation within a spiral arm?
The stars and gas and dust clouds in the disk congregate in a spiral pattern. Star formation occurs in the spiral arms because the gas clouds are compressed in the arms to form stars. The very luminous, short-lived O and B-stars and H II regions around them enhance the spiral outline.
How is star formation related to spiral arms quizlet?
Spiral arms are dynamically stable, sudden compression of gas can trigger the collapse of the gas clouds and the formation of new stars. This stretches the star formation region out into an extended spiral structure.
How many types of spiral galaxies are there?
Spiral galaxies appear as flat, blue-white disks of stars, gas and dust with yellowish bulges in their centers. These galaxies are divided into two groups: normal spirals and barred spirals. In barred spirals, the bar of stars runs through the central bulge.
Why do spiral galaxies orbit faster?
In spiral galaxies the velocities of stars far from the centre are much faster than expected. Normally circular motion is governed by a balance between gravity (pulling the star towards the galactic centre) and an effective centrifugal force (pulling the star outwards).
What force holds the stars in orbit in spiral galaxies?
Gravity
What determines the shape of the galaxy?
The centrifugal force of the spinning gas cloud along with the gravitational pull within the clouds work together to give a galaxy its shape. All galaxies began with an elliptical shape, which is mostly a result of the centrifugal force of the spinning gas cloud.
What is a loose disorganized group of stars?
An open. cluster is a group of star that is loose and disorganized.