Zodiacal Light

Photo credit – Malcol – CC-BY

Cloud of the Day – Zodiacal Light

Photo credit – Brian Minkoff – CC-BY-SA

Brian May played guitar for Queen. That’s Queen, not The Queen, although Queen might have played for The Queen. I don’t know. It seems unlikely, though. On the other hand, Brian May was awarded a CBE (Commander of the Most Excellent Order of the British Empire) in 2005, so maybe he got to play for The Queen after that.

Photo credit – Faulkes – CC-BY-SA

More importantly for our purposes here, May has a PhD in astrophysics. He began his studies as a young man, graduating from London’s Imperial College with a BSc, before beginning his PhD studies on phenomena related to zodiacal light. The success of Queen distracted him from his studies and he wasn’t able to complete his PhD thesis until 2007, more than thirty years later. Fortunately for him, interest in the zodiacal light was so sparse in the interim that his thesis was still valid.

Photo credit – A. Fitzsimmons – CC-BY

Zodiacal light is a faint glow that can sometimes be seen in the sky just before dawn or just after sunset. Sometimes it’s called false dawn because it can fool you into thinking that the Sun is about to rise. Zodiacal light is faint. It’s fainter than the Milky Way. You won’t see it if you’re in a city, or subject to any other light pollution. Even moonlight can wash it right out. The source of zodiacal light is sunlight reflecting off cosmic dust in a disk around the Sun. The disk is flattened by its rotation and lies on the plane of the ecliptic, just like the planets. Hence the zodiac, which is the collection of constellations around the plane of the ecliptic. It’s best observed in spring after evening twilight, and in autumn before morning twilight.