Under Your Skies

4 July 2015

The Milky Way as seen from West Virginia. Forest Wander
The Milky Way as seen from West Virginia.

If you’re a native of the northern hemisphere, the first thing you notice about the night sky in the southern hemisphere is that things are … off. Constellations are missing, the lunar phases seem backwards, and the constellations you do recognize are upside down. It’s very disorientating until you get used to it. But the one thing you do recognize early on is the Milky Way.

Despite claims to the contrary, our solar system is not aligned with the plane of our galaxy. Earth is also tilted about 23 degrees from the axis of the solar system. As a result, the plane of the Milky Way is tilted about 60 degrees relative to the rotational axis of Earth. Because our solar system is about 3/5 of the distance from galactic center, the Milky Way completely encircles our view of the heavens. As a result, no matter where you are on the Earth, there is at least some part of the year when the Milky Way is visible.

Dark cloud constellations of indigenous Chileans. Brian Koberlein
Dark cloud constellations of indigenous Chileans.

This doesn’t mean that all views are equal. The central region of the Milky Way is in the southern region of our sky, which means views in the southern hemisphere tend to be brighter and have more clear contrast between stars and dust clouds. This is likely the reason why many cultures in the southern hemisphere have traditionally created “constellations” out of the shadow regions caused by dust clouds within the Milky Way, such as the Emu in the sky of Australia, or the Llama and Serpent of South America.

But regardless of your place of origin, the Milky Way is a part of your sky. No matter where you roam on Earth, you can always find the Milky Way in the night sky and know that you are home.