The year’s very best meteor shower is usually the Geminids, on Tuesday night, December 13, 2016. This year, there’s some competition.
The Geminids are the sky’s “Old Faithful” when it comes to shooting stars. They produce between one and two meteors every minute. And they’re much slower than those famous summer Perseids or the hit‑or‑miss Leonids because they do NOT strike us head‑on. The Geminids come at Earth sideways. At 20 miles per second, they lope along at half the speed of the other showers. Instead of sharp, brief zaps across the sky, we get leisurely streakers. It’s very appealing.
These meteors are also the most mysterious. All other showers are debris from comets, skimpy stuff less dense than ice. But Geminid meteors are twice as dense, So what could they be? There are other oddities too. All other major meteor showers have been observed for centuries or millennia. But the Geminids were unseen as recently as the Civil War, when it started as a modest shower that delivered only 20 meteors per hour.
The source of these strange fireworks was unknown until 1983, when NASA’s infrared‑detecting satellite IRAS found a small body moving in exactly the same path as these meteoroids. Named Phaethon, it has a speedy orbit that carries it far closer to the Sun than Mercury and then out past Mars into the asteroid belt. Phaethon looks and moves like an asteroid, and yet all other meteor showers are fragments of comets. Very strange. Probably, Phaethon is an odd, has‑been comet, one that completely lost its icy outer covering.
Also unlike the Perseids or Leonids, the Geminids don’t ask you to wait until the hours before dawn. They’re well seen starting at nightfall, although they’re particularly abundant around midnight.
The big problem this year is that the Full Moon is that same night, Tuesday. Its light will hide all but the brightest meteors. So if you don’t see many, maybe shift your focus to the villain, December’s full Moon. It will be 2016’s highest up Moon at midnight, and the brightest full Moon of the entire year.