A cluster of stars in their several millions form a vast collection of gyrating system called Galaxy (Ukaegbu 1998). So, we can say, a Galaxy is a huge collection of millions of stars, together with gas and dust held together by gravitational attraction.
Our Solar system belongs to the galaxy called the Milky Way Galaxy, which contains about 100 to 400 billion stars, one of which is our stars and the sun. The largest globular cluster in the Milky Way Galaxy is the Omega Centauri. All the stars we see at night is in our own galaxy, and it is called Milky Way because it appears as a milky band of light in the sky when you see it from a really dark area.
Apart from our Milky Way Galaxy, there are several galaxies separated by enormous tracts of empty space.
The distance between several galaxies is enormous and is denoted in light years. You can imagine the distance, since light travels at a velocity of 300,000 kilometers per second.
Hubble (1924) in his studies of the universe discovered that galaxies were receding from us in whatever direction we looked in space, implying that the universe is expanding. He also noted that the farther away a galaxy is, the faster it is moving away. This confirms an expanding universe. Findings show that, at a certain point back in time, the Galaxies were closer together.
In summary, the universe is expanding which implies that all matter must have been in one central place about 7 to 9 billion years ago.
*Written by Jennifer N. Elendu for Meziesblog
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