I was poking around on the Internet and stumbled across this time lapse video made by astronaut Don Pettit from the windows of the International Space Station sometime during his stay there from late November 2002 to May 2003. I’ve watched it again and again and am constantly amazed by what you can see. Things to watch for are the aurora borealis snaking along Earth’s circumference, stars rising in the black background of outer space, moonrise and moonlit clouds and the colorful edge of day at the video’s end.
Another curious sight in the video is a thin, orangey-green membrane of light enclosing the planet. This is the airglow or nightglow, a layer of air about 60 miles high where atoms of oxygen, nitrogen and sodium that were ionized by ultraviolet light from the sun during the day recombine at night and emit faint red and green rays of light. Solar UV has the power to knock electrons free from their comfortable orbits around atoms, but once the sun has set, the electrons return and recombine with those atoms, giving off little quanta or bundles of energy as they seek their original positions around the atomic nucleus. The process is called ionization because an atom without its usual complement of electrons is said to be ionized. In human terms, if you had a particularly difficult day at work, you might feel “ionized” by the end of the day. Coming home to a nice meal and glass of wine is equivalent to recombination.
The Big Bear Solar Observatory, located in Big Bear Lake in the San Bernadino Mountains in California uses its 63-inch (1.6m) telescope to study the sun in great detail. The lake creates a very stable atmosphere around the telescope allowing for some of the sharpest, most detailed images of the sun ever. This past week a new adaptive optics system was used on the mirror. Adaptive optics is a technique employed by astronomers to sidestep the blurring effects caused by the atmosphere. A special sensor monitors distortions in the air, sends that information to a computer when then adjusts the shape of the flexible mirror to correct for the distortion. Using adaptive optical systems, astronomers can take pictures nearly as sharp as those made by the Hubble Space Telescope which orbits above the atmosphere.
Using the new setup, the Big Bear folks resolved details on the sun’s surface as small as 50 miles – not bad considering it’s 93 million miles away. Check out that picture – whew, talk about in your face! Sunspots are regions of strong magnetic activity on the sun’s surface or photosphere. They appear dark only because they’re several thousand degrees cooler than their surroundings. This picture shows the classic sunspot structure of dark umbra encircled by the lighter penumbra. The numerous small cells are called granules. Each one is a similar to a air bubble rising in a pot of boiling water. Similar except for size. An average one is 600 miles across or about as big as Texas. They’re driven to the surface by heat from below. The bright part is rising solar gas – mostly hydrogen – while the dark borders are where the gas is sinking back into the sun after having cooled upon reaching the surface. Is that cool or what?