Me and Orion are best buds now. And for good reason. My friend Will and I closed up shop at the Northwoods Starfest near Eau Claire, Wis. Sunday morning at 5 a.m. That glow in the east I thought was the Milky Way was really the sun quietly tiptoeing around the corner. Two nights prior I’d been out till 4:30 Perseid watching. Sumptuous nights of sky watching. A summer sky metamorphoses into winter so easily under the influence of Earth’s rotation. Goodbye Sagittarius, hello Orion.
After clouds and rain Saturday evening, the sky began breaking around 11 o’clock. Our first word of the change was from a woman, I didn’t get her name, who announced loudly that Vega was out. As if playing a little game, thin cracks between clouds taunted us with several tens of seconds of clear sky before closing up again. Peek-a-boo! We quickly and obediently swung our scopes at Mizar, the Ring Nebula, Jupiter. The sky cleared for good after midnight and viewing began in earnest. Perseid meteors flew by all night. Preoccupied with looking through the telescope, I experienced most of them vicariously via the lively shouts of those taking in the bigger picture.
There’s nothing quite like the quiet work of an amateur astronomer attempting to find a new galaxy or star cluster. Steadily and deliberately, those who’ve suffered for months under light polluted city skies, follow their star charts to riches normally denied. I was reminded of the deliberate and considered movements of the slow loris climbing a tree branch at our local zoo. I asked one fellow with a 20-inch telescope if he could find the Saturn Nebula for me. After chart consultations and several telescope adjustments, he invited me over several minutes later to gaze at this remarkable planetary nebula magnified 400 times. All who attended were on a dark safari into the heart of the cosmos.
If you want to meet amateur astronomers, chat about the universe and look through more telescopes than you can shake a green laser pointer at, there’s no better way than attending a star party. Here’s a master list of upcoming events across the U. S. through the remainder of this and into 2011. I hope there’s one near you.
A photo of Saturn’s moons Tethys and Dione got me thinking about winter. Take a look at the difference in tone between the two. Tethys (TEE-thiss) appear brighter because it reflects more light than Dione (DIE-oh-nee), the way snow reflects more light than bare ground. And that’s exactly what scientists think is happening here. Both moons orbit within Saturn’s E ring, a very extensive and diffuse ring that reaches over a half a million miles beyond the three bright inner rings. Among other things, the E ring is composed of relatively fresh icy particles spewed by the geysers of yet another moon, Enceladus (en-CELL-uh-duss). Because Tethys orbits deeper within the E-ring and closer to Enceladus, it sports a heavier coat of the highly reflective ice than Dione and so appears brighter.
I’ve photographed numerous cross-country ski races over the years. When male finishers cross the line, their mustaches wear a heavier coat of frost than their eyebrows for the same reason: mustaches are closer to the source of frosty vapor.
Enceladus is the most likely source for nearly all the particles in the E ring. With over 30 plumes of mist rocketing from fissures near its south pole, there’s plenty of material able to reach escape velocity and spread into a frozen fog across the Saturnian system. Some of the frozen mist falls back to the moon’s surface, making it the most reflective body in the solar system. Enceladus reflects more than 90% of the light it receives back into space; if it wasn’t for its much greater distance from the sun than Earth, it would appear as blindingly bright to our eyes as sunlight on freshly-fallen snow.