December 18, 2015

US10, Halley, and More on Comets

courtesy of Ian Sharp via the Nonfiction Minute

NOW’s the time to track Comet US10! This giant ball of grit and ice was discovered on Halloween 2013. It flew closest to the sun this month and appeared in our northern sky on December 17.
           Comet US10 -- Comet Catalina -- 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
           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. NASA is posting photos of the flyby.  See one from December 12 at  It's not as bright as we might have hoped, but it's thought that US10's tails are HALF a million miles long.

Here's another way to learn more about comets -- try out this fun kitchen comet activity from science author Mary Kay Carson!

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