Galaxy Consensus Notes
1. What is a galaxy?
A system of millions or billions of stars, together with gas and dust, held together by
gravitational attraction
2. What are the main types of galaxy formations?
There are three main types of galaxies: Elliptical, Spiral, and Irregular.
3. What are galaxies made of?
Hundreds of billions of stars, enough gas and dust to make billions more stars, and at least
ten times as much dark matter as all the stars and gas put together. And it's all held
together by gravity.
4. What are the three major parts of a galaxy?
The bulge is a spherical structure found in the center of the galaxy. This feature mostly contains
older stars. The disk is made up of dust, gas, and younger stars. The disk forms arm structures. Our
Sun is located in an arm of our galaxy, the Milky Way. The halo of a galaxy is a loose, spherical
structure located around the bulge and some of the disk.
5. Why are galaxies divided into three major parts?
Gravity is the reason that galaxies have three different parts
6. How do scientists know that galaxies change over time?
Scientists have long figured that galaxies evolve in a hierarchical structure, with mergers
fueling growth, forcing star formation, and altering structure. But the details of the process
remain unknown. In particular, how galaxies smooth out over time is a mystery.
7. What are clusters?
A group of stars or galaxies bound by gravity.
8. What is interstellar matter?
Is the matter that exists in the space between the star systems in a galaxy.
9. What is a quasar?
A massive and extremely remote celestial object, emitting exceptionally large amounts of
energy, and typically having a star like image in a telescope
10. Name 5 different types of stars
- Massive Star
- Average Star
- Red Giant
- White Dwarf
- Planetary Nebula
11.
What is an HR diagram?
The Hertzsprung-Russell Diagram is a graphical tool that astronomers use to classify
stars according to their luminosity, spectral type, color, temperature and evolutionary
stage.