Researchers in the UK have found that neutron-star mountains are less than a millimeter tall. These dense, dead stars are nearly perfectly smooth spheres.
A Jupiter X-ray aurora mystery has perplexed astronomers for decades. Now they think ions responsible for the X-rays "surf" electromagnetic waves into Jupiter's atmosphere.
Observers using a good pair of binoculars or a small telescope can see events called transits on Jupiter, when a moon or its shadow passes in front of the giant planet.
The Mars-Regulus conjunction happens on July 29, 2021. Mars will be 0.7 degrees N. of Regulus. Watch on July 28, too, and look low in the western twilight.