On March 11, 2004, NASA’s Mars Exploration Rover Spirit snapped an eight-second exposure to test its abilities to study the night sky from the martian surface. A portion of the stars in Orion the Hunter, including the three belt stars and bright Betelgeuse, are visible in their familiar configuration at the bottom and right of the image.
NASA/JPL/Cornell
When you look at the sky, you’re seeing a two-dimensional projection of three-dimensional space — the stars are spread out in all directions, including distance, but we don’t get that distance information when we look up (or when we take a photograph). The constellations are simply specific patterns picked out on the sky; they don’t take distance into account. Some stars in a constellation may be close, while others are not. For example, Sirius (Alpha [α] Canis Majoris) is 8.6 light-years away, but Aludra (Eta [η] CMa) is about 2,000 light-years distant. Though these two stars are in the same constellation and appear near each other on the sky, in reality they are thousands of light-years apart.
If you were to travel far enough away from Earth (we’re talking light-years), the patterns would certainly start to change. But because the stars are so distant compared with the size of our solar system (which is just light-hours across), the projection effect — the patterns of stars we see — from Earth holds true on the other planets circling the Sun. From any planet in the solar system, the same constellations we see here on Earth are visible and recognizable. The biggest difference you’d notice is their orientation in the sky (whether they’re high or low compared to the horizon and zenith), which depends on the orientation of a planet’s poles, as well as your location on the planet. Polaris (Alpha [α] Ursae Minoris) is the North Star when viewed from Earth because of the tilt of its poles, but this is not true from the other planets.
Alison Klesman
Associate Editor
