December 5th, 2017, 06:25 a.m. local time
Tuesday brought in a very clear morning sky. For the past several weeks, as I’ve let my dog out in the mornings, I have been scanning the East dawn sky for Jupiter. I finally found it, sticking out high above my largest tree. Welcome back, old friend.
If you observe Jupiter and stars for any amount of time, you learn that Jupiter is “big” compared to any star. This is not a trick of its brightness. As seen from Earth, Jupiter has an angular diameter roughly between 29″ and 51″. For comparison, Betelgeuse in Orion has a angular diameter never above 0.060″. So at Jupiter’s smallest, you would still have line up over 483 Betelgeuses to reach the diameter of Jupiter (as seen from Earth)!
I thought I saw a cluster of light immediately to the right of Jupiter. Could that have been a moon? Later, I looked up the Jovian moon positions for this exact time, and I found it interesting that Io, Europa, and Callisto were all clumped together on Jupiter’s right, at that moment. I am not entirely sure if I really saw the combined light of three moons, but it is pretty cool to think that I may have.