Comet 21P/Giacobini-Zinner came closer to Earth this week than it had in 72 years. Favorite photos here, from the EarthSky community. Plus info on comet Wirtanen, which might become visible to the eye alone later this year.
As wide as 2 Earths – like nothing seen on any other world – Saturn’s hexagon was thought to be a feature of the lower atmosphere, where Saturn’s weather happens. Now there’s evidence it extends high above the cloudtops.