Facts about the Milky Way
- Up until 1920, most astronomers believed that all of the stars in the universe were contained inside the Milky Way. Following this Great Debate, observations by Edwin Hubble proved that the Milky Way is in fact just one of billions of galaxies in the universe.
- The oldest star in the Galaxy is HD 140283, also known as the Methuselah star, and it is at least 13.6 billion years old.
- The Milky Way as a whole is moving through space at a rate of approximately 600 km per second and will collide with the Andromeda Galaxy in around 3.75 billion years.
- The Galaxy has a relatively low surface brightness which means that it is difficult to see from any brightly lit urban or suburban location but very prominent when the Moon is below the horizon.
- If the Milky Way were reduced in diameter to a width of 100 m, the solar system would be no more than 1 mm in width.
- Inside the Milky Way are at least 100 billion planets and anywhere from 200-400 billion stars.
- Surrounding the Galactic disk is a spheroidal halo of old stars and globular clusters – 90% of which lie within 100,000 light-years of the Galactic Center.
- The Milky Way and the Andromeda Galaxy are part of a binary system of giant spiral galaxies belonging to a group of 50 closely bound galaxies called the Local Group.