Saturn is putting in its best appearance of the year this week. The planet is at opposition — it lines up opposite the Sun in our sky. It rises around sunset, and it’s visible all night long. It’s in good view in the southeast by the time the sky gets fully dark. The planet’s also closest to us for the year, so it’s at its brightest — like a bright golden star.
Saturn looks so bright for a few reasons. For one, it’s the second-largest planet in the solar system — nine times the diameter of Earth. For another, its atmosphere is topped by clouds that reflect most of the sunlight that strikes them. Its rings are bright as well, although they’re not at a great angle now.
One thing that works against Saturn’s brightness is its distance from the Sun. It’s about nine and a half times farther from the Sun than Earth is. At that range, the Sun appears just one percent as bright as it does from Earth.
That’s one of a couple of distance-related challenges for spacecraft that study the planet. It takes long exposure times to get good pictures, which means the camera has to turn to track the planet and keep it in sharp view.
Another challenge is that it takes an average of 80 minutes for signals from a craft to reach Earth, and 80 more for a reply to reach Saturn. So a spacecraft has to be able to do a lot on its own, without direction from far-away Earth.
We’ll have more about Saturn’s beautiful rings tomorrow.
Script by Damond Benningfield