You can plan, plan, plan for an astronomical event like last night’s asteroid flyby, and finally succeed in seeing something elusive and amazing. While the sense of satisfaction gained from your efforts is keen, the unexpected offers a different kind of joy. Later that evening while walking the dog, I looked up to see the moon ringed by not one but two halos. The delicate rainbow colors at top and bottom were exquisite, and the whole thing didn’t last more than 20 minutes before thicker clouds mussed it up. Striding alongside the moon was the planet Jupiter, much like the dog at my own side. What a sight!
You may have seen the halo, too. The inner circle was the frequently seen 22-degree halo, which refers to the size of the ring’s radius. If you double that number you get 44 degrees for the halo’s diameter. That’s four and a half fists held at arm’s length against the sky. This is what most of us see when we look up and spot a “big ring” around the moon.
Wrapped around the circular halo was a second or circumscribed halo, which touched the inner halo at top and bottom. That’s where the colors were. Because the outer ring was oval instead of circular, the halo looked very weird – like a giant eye staring back.
Both rings are caused by moonlight bent or refracted by billions of six-sided, pencil-shaped ice crystals in cirrostratus clouds overhead. Each of these tiny prisms contributes to the bending and spreading of light into a ring. Randomly oriented crystals create the 22-degree version, while crystals floating horizontally make the circumscribed halo. I like that as bold and sharp as a halo appears, it’s made of nothing more than light. The color arises from white light being spread into a rainbow spectrum.
If you missed seeing Jupiter close to the moon last night, you have another chance to catch them together this evening. The moon will have moved a fist to the east or left in the interim and shine on the other side of the planet tonight. By tomorrow, the moon will be farther east yet, leaving the planet behind as it travels toward the Seven Sisters Cluster in the constellation Taurus the Bull.
Worrisome news is coming from Russian scientists about the Phobos-Grunt spacecraft. You’ll recall the mission was launched yesterday, but unfortunately, when the probe separated from its rocket stage, it failed to fire its own rockets to leave Earth orbit and head for Mars. The mission’s goal is (was) to retrieve rock samples from Mars’s moon Phobos and return them to Earth in 2014.
The probe and rocket engines are still intact and ready to go, but engineers have only about three days to figure out and fix the problem before Phobos-Grunt’s batteries run out of power. After that it will orbit the Earth like another defunct satellite and ultimately burn up in the atmosphere. There’s also a small Chinese satellite on board that will be sent into orbit to study Mars. Hopefully the troubles will be fixed. If not, it will be Russia’s 4th failed space mission to the Red Planet. I’ll have more information as the story develops.