What is a Galaxy?
A gravitationally bound system of stars, stellar remnants, interstellar gas, dust and dark matter.
The word Galaxy is coined from the Greek word galaxias, literally means “milky”, which is a reference to the Milky Way.
Astronomers believe that there are about 100 to 200 billion galaxies exist in the universe. Examples are Milky Way and Andromeda.
Galaxies range in different sizes from dwarfs with just a few thousand stars to giants with one hundred trillion stars, each obtaining their own center of mass.
Categories of Galaxies based on visual morphology:
- Elliptical
- Spiral
- Irregular
A thought is there that many galaxies have black holes at their active centers.
What is a black hole?
A massive dense object/ region in space; its gravitational field does not allow anything escape from it, not even light within its certain radius.
What is Milky Way?
Milky Way is the large, disk-shaped galaxy including our solar system, usually with a bulge in the center and with arms that spiral outwards as the galaxy rotates. Most of the stars we can see in the sky are in the Milky Way galaxy. In addition to the Sun, the Milky Way contains about 200 to 400 billion other stars. The Milky Way looks like a faint white band in the night sky.
Main Features of Milky Way Galaxy:
- Milky Way is the part of cluster of three dozens of galaxies known as “Local Group”.
- Andromeda is the nearest galaxy to the Milky Way.
- Galactic Plane is the region in space occupied by the Milky Way.
- Our Solar System is in a minor arm known as the Orion Spur/ Orion Arm.
- Major Arms of Milky Way are: Pursues Arm, Sagittarius Arm, Centaurs Arm and Cygnus Arm.
- Our Solar System is nearly 30,000 light years away from the center of the Milky Way.
- Sun takes roughly about 250 million years to orbit around the Milky Way.
- Milky Way galaxy formed about 13.7 billion years ago.
- Milky Way is about 100,000 light years in diameter.
Very Impressive
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