The Milky Way Galaxy
The Sun is a star in the Milky Way galaxy located in a spiral arm about two-thirds of the way from the center of the galaxy.
- Galaxies are made up of gas, dust, and billions of stars and have different shapes
- Elliptical galaxy – spherical or flattened disks,
- Spiral galaxy– a nucleus of bright stars and two or more spiral arms, or
- Irregular galaxy– no definite shape
- Because distances in space are so great that conventional numbers are too large to work with, astronomers use a unit of measurement called light year to measure the distance to stars and galaxies in space. The distance in one light year is equal to the distance light travels in one year.
How many stars are in the Milky Way galaxy?
In one calculation, the Milky Way has a mass of about 100 billion solar masses, so it is easiest to translate that to 100 billion stars. This accounts for the stars that would be bigger or smaller than our sun, and averages them out. Other mass estimates bring the number up to 400 billion.
What kinds of galaxies are there in the Universe?
Can you identify each galaxy type below?
How many galaxies are in the Universe?
According to the best estimates of astronomers there are at least one hundred billion galaxies in the observable universe. They've counted the galaxies in a particular region, and multiplied this up to estimate the number for the whole universe.
The Universe is BIG....really, really, really, big!
Below is a picture of 10,000 galaxies taken by the Hubble telescope.
Each galaxy is composed on billions of stars and solar systems like our own!!
Peering deep into the early universe, this observation from the NASA/ESA Hubble Space Telescope reveals thousands of colorful galaxies swimming in the inky blackness of space. A few foreground stars from our own galaxy, the Milky Way, are also visible.
Distances in space are so vast scientists use
light years to measure distance.
Light travels 186,000 miles in 1 second!
Light travels 6,000,000,000,000 (trillion) miles in one year!!
How do we measure distances in space?
Size comparison of everything known in the Universe!