A gem of a meteor shower

The spectacular Geminid meteor shower peaks the night of December 13/14. Although often considered a poor cousin to August’s Perseid shower, the Geminids typically put on a better show. That’s the case this year, when observers can expect to see up to 120 “shooting stars” per hour — an average of two per minute — under a dark sky.

“Conditions couldn’t be better for the Geminids this year,” says Astronomy magazine senior editor Michael Bakich. The shower peaks under a slim crescent Moon, whose feeble light won’t interfere much even after it rises around 3:30 a.m. local time. The best views will come between roughly midnight and 4 a.m., when the rate peaks and the area from which the meteors appear to radiate passes nearly overhead.

Any stray light in the sky tends to drown out fainter meteors, so find an observing site far from city lights. A large field is ideal because you can then let your eyes roam across the whole sky. December nights tend to be cold, however, so bundle up in layers. Reclining in a lawn chair is a great way to take in a lot of the sky at once, but be sure to get up and walk around occasionally. It also helps to drink some hot coffee or tea.

The Geminids begin as tiny specks of dust that hit Earth’s atmosphere at 22 miles per second, vaporizing from friction with the air and leaving behind the streaks of light we call meteors. The meteors radiate from the constellation Gemini the Twins (hence their name), near the bright stars Castor and Pollux. They can appear anywhere in the sky, however, and actually leave longer trails the farther from the radiant they are.

The tiny bits of rock and debris that produce the Geminids are believed to originate from a small, 3-mile-wide asteroid named 3200 Phaethon, which was not discovered until 1983 (while the annual Geminid shower has been recognized since 1862). Every 1.4 years, Phaethon’s orbit takes it closer to the Sun than any other known asteroid, heating its surface to roughly 1,300 °F (700°C).

This extreme heating is believed to cause Phaethon to crack and shed debris, which then sparsely spreads out all along the asteroid’s orbital path, much like a flowing river of pebbles. Though Phaethon’s orbit around the Sun takes 1.4 years, Earth passes through Phaethon’s river of debris every December, which ultimately produces the beautiful Geminid shower we have grown to know and love.