Understanding Our Universe

Study Notes

Students will be able to explore and understand the terms star, galaxy, Milky Way, and black holes after studying this chapter.

The word galaxy comes from the Greek word "gala" meaning "milk".
Our galaxy, the Milky Way, looks like a milky cloud in the night sky and is a spiral type galaxy.
It has mostly old stars at its center, surrounded by a halo of newly generated stars.
The Milky Way has more than a billion stars and circles the whole sky.
Our Sun and its solar system are situated in one of its spiral arms.
The stars we see at night are part of the Milky Way Galaxy.
There is still enough gas and other matter in its arms for many more generations of stars.

Astronomers collect information about astronomical objects using radio telescopes.
Astronomy is a very old science that has evolved from studying objects seen in the night sky to studying the whole universe.

Stars are large distances apart, and a light year is the unit of distance used to measure their distances.
A light year is the distance light travels in one year, which is approximately 9.5 trillion kilometers.

Andromeda is our neighboring galaxy, visible to the naked eye on a clear night.
It is bigger than the Milky Way and situated about 2.5 million light years away from us.

There are several types of galaxies, including spiral, elliptical, jellyfish, and irregular galaxies.
Spiral galaxies have a flat disk-like shape with a bulge in the middle and rotate about their center.
Elliptical galaxies are oval-shaped, contain mostly old stars, and do not rotate around their centers.
Jellyfish galaxies have giant tails of young stars extended away from the galaxy disk.
Irregular galaxies do not have a distinct regular shape.