Description: A Galaxy is a collection of stars, dust, gas, planets, and dark matter.
galaxy (503) milky way (75) hubble (48)
An elliptical galaxy taken hubble telescope with x-ray lights. Many more different types of galaxies can be seen in the background. A galaxy is a collection of stars and planets, gas and dust, and dark matter, all held together in a gravitational pull, and orbiting around a central point of gravity. Kind of like our solar system, but on a MUCH larger scale.
The concept of a galaxy was first described by the Greek philosopher, Democritus. He suggested that the light band across the night sky (known as the 'Milky-Way' was actually a collection of stars.
When Galileo Galilei studied the Milky Way in 1610, he proved that it was in fact made up of a very large number of stars. In 1755, Immanuel Kant theorized that the stars we see (including our own Sun) was a collection of stars and solar systems that rotated around a central, gravitational point—it was our galaxy.