The earth and the solar system are part of the Milky Way galaxy. Part of our galaxy can be seen in the sky on a dark night. It appears as a band of light that stretches across the night sky. The Milky Way is just one of many spiral galaxies that exist in the universe.
A Spiral Galaxy
The Milky Way is a spiral galaxy. There are 100 – 400 billion stars in this galaxy.
Supermassive Black Hole: The width of the Milky Way is about 100,000 light years in diameter. At the center of the galaxy, there is a large bulge. Scientists believe that a super massive black hole lies in the center of that bulge. The earth is about 27,000 light years away from the galactic center. Our solar system is located in one of the spiral arms of the galaxy.
Spiral Arms: The galaxy is thought to have 4 large spiral arms. These arms contain a great amount of gas, dust and stars. As a result, the spiral arms are an area of star creation.
Halo: In addition to the bulge and the spiral arms, the Milky Way is surrounded by a halo of hot gas and older stars.
Stars in the Galaxy
The most common type of star in our galaxy is the red dwarf. This type of star is smaller, older and cooler than our sun. The earth and the stars revolve around the center of the galaxy once every 240 million years.
The Milky Way is on a collision course with the neighboring Andromeda galaxy. Within the next 4 billion years, the two galaxies are expected to collide. Scientists believe that similar collisions have taken place in the past.
Reflections
Vocabulary
- black hole
- galaxy
- Milky Way
Notes
- The Milky Way is a spiral galaxy.
- The solar system is located 27,000 light years away from the center of the Milky Way.
- The Milky is likely to collide with another galaxy in the future.
