Final answer:
Galactic types include spiral, elliptical, and irregular, each with distinct structures and properties. Spiral galaxies like the Milky Way have younger stars and more interstellar material, while elliptical galaxies typically feature older stars and minimal gas and dust. The center of our galaxy likely hosts a supermassive black hole.
Step-by-step explanation:
There are three main types of galaxies: spiral, elliptical, and irregular galaxies.
- Spiral galaxies have distinctive spiral arms that wind outward from a central bulge. They contain both old and younger stars and considerable amounts of gas and dust which facilitates ongoing star formation. The Milky Way, the galaxy that contains our solar system, is an example of a spiral galaxy.
- Elliptical galaxies range from nearly spherical to slightly elongated and consist predominantly of older stars. They have minimal gas and dust and, consequentially, little to no new star formation. Ellipticals are typically more massive than spirals.
- Irregular galaxies lack a clear shape and are often chaotic in appearance, often resulting from galactic interactions or mergers. They can contain a mix of old and young stars, as well as significant amounts of interstellar material.
The age of the stars in galaxies can indicate the galaxy's history of star formation. Spiral galaxies, with their abundance of gas and dust, often host younger stars, while elliptical galaxies contain a more aged star population.
Our galaxy, the Milky Way, is categorized as a spiral galaxy. Notably, the center of the Milky Way is thought to house a supermassive black hole, which is supported by evidence such as the orbits of stars at the galactic center and the presence of high-energy phenomena.