Have you ever wondered what the night sky might look like on a planet outside the Milky Way? Imagine the sight of the entire galaxy hanging in the sky above you.
It might look a little like this…
Composite image made up of: Crystal Lake, California (Mountains), Silverado, NGC 3370 & Andromeda (Spiral Galaxy), NGC 1313 (Irregular Galaxy).
View from a hypothetical planet orbiting a star in the outer region of the Small Magellanic Cloud (SMC). The SMC hangs in the sky (right), with the Milky Way in the background (left).
One of the stars I’m studying is in the Magellanic Clouds — two small irregular galaxies close to the Milky Way. On a hypothetical planet around this star, the sky would be an awesome sight to behold. The planet itself would be bathed in a near perpetual twilight, by the light from the Milky Way’s 200 billion stars. The galaxy would almost certainly be bright enough to cast shadows, and possibly even be visible during the day. In the foreground, the closer of the two magellanic clouds looms, similar in apparent size but only because it’s much much closer.
The Magellanic Clouds are in the process of tearing each other apart, while simultaneously being shredded by the vast gravitational pull of the Milky Way itself. The star’s in a region called the Magellanic Bridge. A stream of gas, dust and stars trapped in a tug of war between the two smaller galaxies.
During the few hundred million years while these galaxies have been in our neighbourhood, they’ve been gradually siphoned away into our own galaxy, via a huge channel called the Magellanic Stream. The Magellanic stream is huge. It spans nearly 180° of the sky, but you can’t see it — it’s mainly made up of hydrogen gas, with a few stray stars caught up in the pull. A huge dark streamer in the night.
This radio telescope image (which I can’t take credit for) shows the molecular gas in the Magellanic Stream. The two bright spots on the left are the galaxies themselves.
Image Credit: M.E. Putman (University of Colorado), L. Staveley-Smith (CSIRO), K.C. Freeman (Australian National University), B.K. Gibson (Swinburne University) and David G. Barnes (Swinburne University)