I know. You’re probably got PANSTARRS fatigue. Still, I can’t help but direct your eyes once again to yet another wonderful photograph, this one made by Italian amateur astronomer Lorenzo Comolli. Like many of us, he lives in a light polluted area and must escape to find darker skies. For Lorenzo that means a trip to the Alps or Apennines.
His spectacular image was made using a 5.5-inch (140mm) wide-field refractor, a sensitive CCD camera and seven images. Each exposure lasted 2 minutes during which time he carefully guided the telescope to follow the comet’s motion across the star field. Lorenzo then stacked all seven images one atop the other in an photo program like Photoshop to create a single, high resolution photo.
Astrophotographers prefer stacking a series of short-exposures instead of making one long exposure because it reduces noise (graininess) and the effects of light pollution. A 14-minute time exposure picks up more unwanted light than a 2-minute one.
Studying the picture we’re struck by the fan-like spread of multiple plumes of dust released by the comet as the heat of the sun vaporizes dust-laden ices. Cometary dust particles are extremely small, ranging in size from less than a micron (equal to one-thousandth of a millimeter) to 1/100 of a millimeter. For comparison, particles in wood smoke fall in the same range. Sunlight pressure physically pushes these tiny motes back to form the tail.
The real eye-catchers are the synchronic bands. Our best model points to their formation from individual fragments or chunks that break up once they’re released from the comet. As each new fragment crumbles into fine dust, it’s raked into a fresh by sunlight. I think you would agree the end result of such a simple process is breathtaking.
Comolli’s picture also records a dim tail made of sodium atoms, possibly released by collisions between dust grains flying off the comet’s nucleus, and a second dust tail of larger particles trailing behind the comet as it moves along its orbit around the sun. For more of Lorenzo’s images of Comet PANSTARRS, click HERE.
Uwe Pilz of Leipzig, Germany has created a wonderful series of simulations of PANSTARRS’ tail that reveal how dust particles are sorted according to size across the comet’s multiple tails.
I’ve used his information to help you see what’s where in Lorenzo’s photo. Again for reference, a typical bacterium is between 0.2 and 3 microns across (same as fine comet dust!), a human red blood cell 5 microns and a human hair is about 75 microns but varies by hair type.
While most of us will never see such such riches through our telescopes and binoculars, we can appreciate this hidden side side of PANSTARRS that superb amateur photography can reveal.