Kerrie Logan Hollihan
Teaching the Power of Wonder
Comet US10 is visible before dawn. With good binoculars, you should be able to track it later in December as it streaks northward.
On New Year’s night the comet will be visible near Arcturus, our fourth-brightest star. Look northward toward Ursa Major and the Big Dipper. Arcturus lies west and south as you follow a curve formed by the Big Dipper’s handle. Learn more about Comet US10 on Sky & Telescope magazine’s website at http://www.skyandtelescope.com/observing/bright-comet-prospects-2015012815/
Comets are balls of grit and ice thought to be nearly as old as the universe itself. One astronomer described comets as “dirty snowballs.” They are roughly 25 percent dust particles and 75 percent ice, with a good measure of ammonia, methane, and carbon dioxide thrown in.
Many comets are born in the Oort Cloud, a cold, giant cloud of particles on the outer edge of our solar system. Astronomers think that gravity from a passing star kicks a comet out of the Oort Cloud and into the sun’s gravitational field. Other comets might originate in the Kuiper Belt, a region of small icy objects and worlds, including Pluto, that ring the solar system out beyond Neptune.
Our best known comet is Comet Halley, named for the early scientist Edmond Halley. In the late 1600s, Halley used the secret mathematics of Sir Isaac Newton to learn how comets journey through space. Halley learned that comets don’t travel in straight lines, as most folks thought. Halley used just pen and paper to create a giant database of 24 comets that he saw through a telescope or read about in ancient books.
Halley found that the paths of three comets were actually very long ellipses, flattened ovals. Then he guessed that these three -- the Comets of 1531, 1607, and 1682 -- were all the same comet that showed up every 76 years.
Sure enough, in 1758, the comet again appeared. “Halley’s Comet” has returned steadily ever since. It appeared in 1835, 1910, and 1986. Mark your calendar for its next swing by Earth in 2061. As for Comet US10, this is your last chance. It won’t be back for millions of years!
-- National Science Teachers Association
For more information about Kerrie, visit her website by clicking here.