Sky ArchiveTonight

Visualize the sun’s path through Milky Way

Tonight, use the brilliant star Sirius – and, if you’re in the Northern Hemisphere, the star Vega – to imagine the direction our sun and solar system are traveling through space. The sun in its orbit is traveling away from Sirius and toward the star Vega. So if you stand outside at dusk or nightfall with your back to Sirius – facing northwest, Vega’s direction at that time – you’ll be facing the direction our solar system moves through the Milky Way galaxy. Cool, huh?

Vega can’t be seen from the Southern Hemisphere in the evening right now, and Sirius is much higher overhead as seen from there, but the principle remains the same. When you look at Sirius – easy to find as the sky’s brightest star – you’re looking backwards along our sun’s path through the Milky Way.

Tonight’s chart, and the photo below, both can help you be sure you’re seeing Sirius. The brightest star of nighttime – Sirius – shows up close to the horizon in early evening, rising upward as evening deepens into night. You can always be sure you’ve found Sirius if a line through the three stars of Orion’s Belt point to it.

By the way, the direction to the star Vega – the general direction toward which our sun is traveling through space – is called the solar apex or sometimes the apex of the sun’s way.

Read more: How long does it take our sun to orbit the Milky Way’s center?

View larger. | No matter where you are on Earth, the three stars of Orion’s Belt always point to Sirius on our sky’s dome. Here they are rising over Madeline Island in Lake Superior (USA). Jim Peacock captured this scene.

Bottom line: Sirius is easy to find. It’s the sky’s brightest star on the sky’s dome. When you look at it, you’re looking backwards along our solar system’s path through the Milky Way galaxy.

Donate: Your support means the world to us

January 20, 2017
Sky Archive

Like what you read?
Subscribe and receive daily news delivered to your inbox.

Your email address will only be used for EarthSky content. Privacy Policy
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

More from 

Editors of EarthSky

View All