A coronal mass ejection that left the Sun on Monday is likelyto buffet Earth’s magnetosphere later this week. Forecasters estimate a 20% chance of severe geomagnetic activity when the CME arrives. Auroras are possible early Thursday and Friday mornings.

A near-Earth asteroid, 2000 YA, has just been detected and will pass within two lunar distances of Earth on Dec. 22nd. There’s no danger of a collision, say scientists, but the small space rock will be near enough to see through large amateur telescopes or through small telescopes equipped with CCD cameras.