Astro Bob blog: Crystal blue occasionOne more "free day" to watch the shuttle and space station together. More on the Wisconsin meteorite, ashy sunsets and ice crystal art.
By: Bob King, Duluth News Tribune
Crystal blue occasion
Looks like we're going to get one more opportunity to see the cat-and-mouse play of shuttle and space station. NASA called off the landing of the Discovery shuttle this morning in Florida because of clouds. The next landing window will be tomorrow at 6:34 a.m. Central time which means we'll see the dynamic duo for another go-around Tuesday at dawn. For Duluth and region, the space station will slowly arc across the northern sky starting at 4:46 a.m. Discovery will follow the same track a minute or two earlier. I don't have an exact time for the shuttle because the sites devoted to pass time predictions assumed it already landed. I'll monitor those sites into the evening so please check back for an update.
An unusual aspect of this shuttle landing is that it will make a rare descent pass across the heart of the U.S. Observers in the West can see it as a brilliant "meteor" in a dark sky while those in Central and Eastern parts of the country will see the show in twilight and around sunrise. If you live near the path shown on the NASA TV map above and clear skies are forecast, don't miss this chance. Imagine -- you can watch a pass before dawn and then a couple hours later see the shuttle head for a landing in Florida. "Mach" in the map refers to the speed of sound. Mach 22 is 22 times the speed of sound. For exact viewing times for your area, please click HERE and fill in your zip code.
This is a fresh 36 gram meteorite from the Wisconsin fall found by Mike Farmer recently. Photo courtesy Michael Johnson
Meteorite hunters continue to find more meteorite fragments dropped by last Wednesday's fireball across Wisconsin. So far about 2 1/2 pounds have been recovered. I may soon add my name to the list of those combing farm fields and roadways but more on that tomorrow.
A volcanic sunrise and its reflection on the River Mersey over Runcorn Cheshire in the UK. The photo was taken this past Saturday. Credit: Vincent Phillips
A couple days ago I mentioned that the ash from the Iceland volcano has made sunsets in Europe much more colorful than usual. All the ash and sulfur compounds in the atmosphere scatter the shorter wavelengths of sunlight -- violet, blue and green -- leaving only the reds and oranges to color the sky. We see this at every sunset and sunrise to some degree as sunlight is filtered by the thicker, dustier air near the horizon. Add ash and sulfur and you create more obstacles for sunlight and even richer colors.
You might be wondering if any of this ash will make it further than Europe perhaps even to the U.S. That depends on many factors including how long the eruption lasts as well as the prevailing winds. Keep your eye open and if you see unusually vivid sunsets and sunrises, drop me an e-mail at firstname.lastname@example.org.
This photo, taken Monday morning, shows a classic 22-degree solar halo, a rarer circumzenithal arc and one sundog. All are caused by refraction in ice crystals in high clouds. Photo: Bob King
Although not as dramatic as a volcanic eruption we're having some ice crystal-related sun fun in the Duluth region today. As I write this, a solar halo has been ringing the sun since shortly after sunrise. A large mass of cirrostratus clouds is moving through the region. These high clouds are composed of millions of microscopic, hexagonal ice crystals that work together to refract or bend light into a circle around the sun. Earlier around 8 a.m. there was a rarer apparition -- a circumzenithal arc. This rainbow-tinted arc is about double the distance from the sun of a typical halo and can be extremely colorful. This particular one was muted, but the colors were still apparent.
If you can picture the ice crystals as chopped up lengths of pencils, which are hexagonal in cross section, light that passes through the top of the crystal and passes out the side causes the arc while light passing through one side of the crystal and out another side creates the more common halo.
There was even a sundog, another refraction effect, embedded in the one side of the halo. As long as high clouds persist, it's a good idea to stick out your arm, block the sun and scan the sky around it for signs of crystal light.