The Milky Way Galaxy

What is the Milky Way?

• A galaxy is a group of billions of stars, planets, gas, and dust held together by gravity.
• The Milky Way is a galaxy that contains Earth and is special because of its unique features.
• The galaxy contains billions of stars of all types, including white giants and neutron stars.
• Planets exist in abundance, orbiting around many of the stars in the galaxy.
• The interstellar medium contains dust and gas, including hydrogen, helium, oxygen, and carbon.

Milky Way Galaxy History

• The Milky Way galaxy started around 13.5 billion years ago when gravity pulled the parts of the galaxy together.
• The stars orbit around the center of the galaxy, just as the planets in our solar system orbit around the sun.
• Astronomers believe a supermassive black hole exists at the center of the galaxy.
• The galaxy spun and flattened out into a disk shape, with a central bright region called the galactic bulge.

What Type of Galaxy is the Milky Way?

• The Milky Way is a barred spiral galaxy, with a central bulge and arms that spiral out from the center.
• Spiral galaxies are disc-shaped rotating galaxies with a central bulge and arms.
• Barred spiral galaxies have a large, bright bar of stars that cut across the center.

How Big is the Milky Way?

• The size of the Milky Way galaxy is about 100,000 light-years across.
• It would take 100,000 years to travel from one end to the other at the speed of light.
• Going from top to bottom would only take about 1,000 light-years.

How Many Stars are in the Milky Way?

• The Milky Way contains anywhere from 100 to 400 billion stars.
• The core of the galaxy, in the galactic bulge, is a dense region of stars that are extremely old, many of them 7 billion years or older.
• There are approximately 10 billion white dwarf stars and one billion neutron stars in the Milky Way.

What Galaxy Do We Live In?

• The Earth, sun, and all the planets in our solar system are a part of the Milky Way galaxy.
• The sun is located in one of the spiral arms that come off of the core of the Milky Way.
• Almost every star has at least one or more planets orbiting it, making the number of possible planets in the galaxy somewhere in the trillions.