What is a Spiral Galaxy?

Table of Contents☰

About Spiral Galaxy:

Spiral galaxies are twisted collections of stars and gas that often have beautiful shapes and are made up of hot, young stars.
In a spiral galaxy, the stars, gas, and dust are gathered in spiral arms that spread outward from the galaxy’s center.
Most of the galaxies that scientists have discovered so far are spiral galaxies, as opposed to the other two main categories of galaxy shapes—elliptical and irregular.
Approximately 60% of all galaxies are thought to be spiral galaxies.
The Milky Way, the galaxy that includes Earth and our solar system, is an example of a spiral galaxy.
Structure:
- Most spiral galaxies contain a central bulge surrounded by a flat, rotating disk of stars.
- The bulge in the center is made up of older, dimmer stars and is thought to contain a supermassive black hole.
- Approximately two-thirds of spiral galaxies also contain a bar structure through their center, as does the Milky Way.
- The disk of stars orbiting the bulge separates into arms that circle the galaxy.
- These spiral arms contain a wealth of gas and dust and younger stars that shine brightly before their quick demise.
The majority of spiral galaxies rotate in the sense that the arms trail the direction of the spin.
The visible portion of spiral galaxies contains only a small fraction of the total mass of the galaxy, and that spiral galaxies are surrounded by an extensive haloconsisting mostly of dark matter.
Spiral galaxies are thought to evolve into elliptical galaxies as the spirals get older.

Q1: What is a Black Hole?

A black hole is a region in space where gravity pulls so much that even light cannot get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying. Because no light can get out, it is difficult to detect a black hole. The largest black holes are called “supermassive.” These black holes have masses that are more than 1 million suns together.

Source: Spiral galaxy 59 million light-years away looks like this: NASA shares stunning video of ’young, hot stars’