What causes galaxies to be spiral?

What causes galaxies to be spiral?

Astronomers believe that galaxies have spiral arms because galaxies rotate – or spin around a central axis – and because of something called “density waves.” A spiral galaxy’s rotation, or spin, bends the waves into spirals. Stars pass through the wave as they orbit the galaxy center.

How does the evolution of spiral galaxies differ from the evolution of elliptical galaxies?

Elliptical Galaxies The major difference between elliptical and spiral galaxies is that ellipticals lack a significant disk component. Thus, an elliptical galaxy has only a spheroidal component and looks much like the bulge and halo of a spiral galaxy.

Why do some elliptical galaxies appear circular?

Elliptical galaxies are rounded, featureless collections of old stars that contain very little gas and dust. They come in a range of different sizes and shapes, and can appear circular (as shown here), oval or even rugby-ball shaped. With the gas and dust long since gone, there is no material left to make new stars.

Does an elliptical galaxy rotate like a spiral galaxy explain?

Unlike spiral galaxies, elliptical galaxies are not supported by rotation. The orbits of the constituent stars are random and often very elongated, leading to a shape for the galaxy determined by the speed of the stars in each direction.

Do elliptical galaxies have spiral arms?

Elliptical galaxies lack the swirling arms of their more well-known siblings, spiral galaxies. Instead, they bear the rounded shape of an ellipse, a stretched-out circle.

How do barred spiral galaxies form?

Bars form when stellar orbits in a spiral galaxy become unstable and deviate from a circular path. “The bar becomes even stronger as it locks more and more of these elongated orbits into place. Eventually a high fraction of the stars in the galaxy’s inner region join the bar.”

How does the evolution of spiral galaxies differ from the evolution of elliptical galaxies quizlet?

Spiral galaxies have both young and old stars, whereas elliptical galaxies have only old stars. Among the large galaxies in the universe outside of clusters, most are spiral. Elliptical galaxies are bluer and contain more dust than spiral galaxies.

How old are elliptical galaxies?

The accepted belief on the mass assembly history of massive elliptical galaxies based on their stellar population leads to an age between 7 and 10 billion years old.

How do elliptical galaxies rotate?

Why do two colliding spiral galaxies form an elliptical galaxy?

Q: Why do two colliding spiral galaxies form an elliptical galaxy rather than one larger spiral galaxy? A: When two spiral galaxies collide, gravity is the main force that comes into play. As the galaxies approach each other, gravitational forces start to pull the stars, gas, and dust of the spiral arms out of their original orbits.

What is the evolutionary cycle of galaxies?

Galaxies exhibit an evolutionary cycle, where they begin in something like a quasar form, settle into a semi stable spiral form, and finally age into elliptical galaxies. Elliptical galaxies and spiral galaxies have evolutionary tracks which branched off differently from their proto stages.

How do galaxies interact with each other?

As the galaxies approach each other, gravitational forces start to pull the stars, gas, and dust of the spiral arms out of their original orbits. This is what causes the warped shape of famously interacting pairs such as the Mice (NGC 4676) and the Antennae Galaxies (NGC 4038 and NGC 4039).

What happens to a galaxy after it merges?

During the merger, the stars become scattered and their orbits become random. This is what results in a single, football-shaped elliptical galaxy with stars orbiting the center in all planes, rather than the single plane of a flat spiral galaxy.