On Sunday, Dec. 16, the comet known as 46P/Wirtanen will make one of the 10 closest comet flybys of Earth in 70 years, and you may even be able to see it without a telescope. Although the approach will be a distant 7.1 million miles (11.4 million kilometers, or 30 lunar distances) from Earth, it's still a fairly rare opportunity. "This will be the closest comet Wirtanen has come to Earth for centuries and the closest it will come to Earth for centuries," said Paul Chodas, manager of the Center for Near-Earth Object Studies at NASA's Jet Propulsion Laboratory in...