Milky Way

The Milky Way is the galaxy in which we all live, but because the Sun is located within the Milky way, we cannot see its actual shape. All we see is as a faint, white band stretching across the night sky. The name comes from the Latin, Via Lactea, which literally means "milky path". On closer inspection, we can see that the milky band is made up of billions of distant stars, but that much of the light is blocked out by gas and dust in the plane of the galaxy.

Hubble Tuning Fork
Full-sky composite image of the Milky Way Galaxy
  Credit: Gigagalaxy Project

 

Observations suggest that the Milky Way is a barred spiral galaxy with at least 200,000,000,000 (200 billion) stars in it. It is around 100,000 light-years in diameter and around 1000 light-years thick on average. The Sun can be found in a fairly remote and dark region of the galaxy, around two-thirds of the way out from the centre.

 

The plane of the Milky Way is inclined by about 60° to the ecliptic (the plane of the Solar System), with the centre of the galaxy located in the direction of the Sagittarius constellation.

In the same way that the Earth orbits the Sun, the Sun orbits the Milky Way at a speed of around 220 km/s. However, because of the vast distances involved, it takes our Sun around 225 million years to complete one full orbit.