The Milky Way is the name given to the galaxy in which our Solar System is located.
It is called this because of how it looks when viewed from Earth.
A galaxy is a large group of stars bound together by gravity.
How big is the Milky Way?
The Milky Way is a spiral galaxy that contains approximately 100 billion stars.
These stars form a large disk with a diameter of about 100,000light-years.
Our Solar System is about 25,000 light-years away from the center of the Milky Way.
Our planetary system is the only one officially called a ‘Solar System,’ but astronomers have discovered more than2,500other stars with planets orbiting them in our galaxy.
How do we know what the Milky Way looks like?
As the Earth exists within the Milky Way, it may seem strange that we claim to know what it looks like.
However, astronomers have discovered clues as to the shape of the Milky Way in the night sky.
One clue is the bright band of stars that can be seen across the night sky in certain areas.
Using telescopes to take photographs from different angles and create a panoramic view, scientists deduced that the concentration of stars supported the theory that our galaxy was a spiral.
If it weren’t, we would see stars spread across the sky, not predominantly in a single band.
The structure of the Milky Way
The Milky Way was previously believed to be a spiral consisting of four arms.
However, scientists have discovered that just two arms dominate the Milky Way’s structure using infrared images from NASA’s Spitzer Space Telescope.
NASA has officially located our solar system near a partial arm of the Milky Way called the Orion Arm.
