CATCH a moving comet
COMETS ARE PERHAPS the oddest denizens of the Solar System. Most appear with little warning, put on a modest show, then race back to the Oort Cloud, not to be seen again for many, many years. Part of their allure is that each is unique and doesn’t always follow predictions about its brightness and activity. Some, like 17P/Holmes, defy conventional wisdom and unexpectedly attain naked-eye visibility even when located relatively far from the Sun. Others fail to live up to their advance billing, with some inevitably disintegrating as they near our star.
All this uncertainty is part of the challenge that has kept me actively photographing comets for more than 30 years.
Dirty iceballs
These dusty chunks of ice and gravel are leftover material from the formation of our Solar System. When a comet passes close to the Sun, the comet’s surface can warm enough to sublimate its frozen gases, producing an expansive atmosphere known as the coma. Brighter comets typically develop a tail or sometimes two. One tail, comprising gases that stream away from the direction of the Sun, is called the ion tail. Such tails usually appear bluish and can display fast-moving knots that change appearance over short timespans.
The other tail commonly seen in comets is made of small dust grains and gravel-sized particles are generally colourless and often appear featureless, though some contain visible striations.
