What are Galaxies?
Did you know that galaxies are the vast islands of stars filling space? Our own spiral-shaped Milky Way, parts of which can be seen on clear nights streaking across the sky, contain hundreds of billions of stars.
Here Are 3 Fun Facts about Galaxies:
- The word ‘galaxy’ is derived from the Greek word galaxias which means “milky”, it is a reference to our own galaxy the Milky Way.
- There are potentially more than 170 billion galaxies in the observable universe. Some, called dwarf galaxies, are small with about 10 million stars, while others are huge containing an estimated 100 trillion stars.
- Based on shape astronomers have identified various kinds of galaxies including, elliptical galaxies, spiral galaxies, lenticular galaxies, and irregular galaxies.
Can you Identify These Galaxies??
- Spiral galaxies are rotating flattened disk-shapes with at least two spiral arms of newer stars extending out from a central bulge of older stars. The dense molecular clouds of hydrogen gas and dust in the spiral arms of spiral galaxies are areas of intense star formation.
See a sample image here: https://apod.nasa.gov/apod/ap031103.html
- Barred spiral galaxies (like our Milky Way) contain a long bar in the middle with spiral arms coming off the ends. Around two-thirds of spiral galaxies contain a barred structure in their center.
See a sample image here: https://apod.nasa.gov/apod/ap181009.html
- Elliptical galaxies are a mass of stars bunched together in the shape of an elliptical disk.
See a sample image here: https://apod.nasa.gov/apod/ap060520.html
- A lenticular galaxy is a type of galaxyintermediate between an elliptical and a spiral galaxy in classification schemes. It contains a large-scale disc but does not have large-scale spiral arms.
See a sample image here: https://apod.nasa.gov/apod/ap020408.html
- Irregular galaxies are any galaxy that has no obvious spiral or elliptical structure. Some irregular galaxies would have just formed that way while others are the result of other galaxy types crashing into each other.
See a sample image here: https://apod.nasa.gov/apod/ap180921.html
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