A screenshot of the Earth (blue orbit) crossing the debris stream (sparkly white path) left by comet 8P/Tuttle during the comet's 14-year orbit around the Sun. Image Credit: Ian Webster
Two days before Hanukkah and three before Christmas, the cosmos will bring you an early holiday gift—no telescope required. The Ursid meteor shower peaks in the early morning hours of December 22, after midnight through dawn. It's not the most spectacular shower of the year, but it is the last one of 2016, and it'll tide you over until the Quadrantids next month. (And making a big production of going outside to watch the sky is a pretty good way to drop a big hint about that telescope you want for Christmas or Hanukkah.)
Danielle Moser, a meteor scientist with the Meteoroid Environment Office at NASA's Marshall Space Flight Center, tells mental_floss that you can expect to see a handful of meteors if you're patient. "Not all of the meteors you’ll see while out observing belong to the Ursid meteor shower—some are sporadic background meteors and some belong to other active showers. If you see a meteor, try to trace it backwards. If you end up near the Little Dipper, there’s a good chance you’ve seen an Ursid."
HOW 8P/TUTTLE WAS DISCOVERED… TWICE
The Ursids among the constellations. Image Credit: Stellarium
While some meteor showers have been studied for millennia, the Ursids have only been observed for a relatively short time. The shower's parent is comet 8P/Tuttle, discovered in 1790 by Pierre Méchain. Decades later, in 1858, it was rediscovered by Horace Tuttle, and thus earned its name. (Don't feel bad for poor Pierre, though. He discovered so many things in his lifetime that he probably wouldn't remember this meager little comet anyway.)
Around the turn of the century, William Denning, an amateur astronomer and renowned comet hunter from England, recognized the radiant, or the seeming point of origin, of the Ursid meteor shower. The association with the Tuttle comet was immediately suspected, and later observations would confirm it.
It turns out Tuttle is a "contact binary"—a small, solar system object made of two bodies that have gravitated toward each other until they touch, like the rubber-ducky shaped 67P/Churyumov–Gerasimenko. We know now that Tuttle's orbit around the Sun takes just under 14 years. As it goes about its orbit, it leaves behind a trail of particles that, over the centuries, has organized. When the Earth crosses into this debris field, those particles slam into our atmosphere and burn away. That release of energy takes the appearance of "shooting stars." A meteor shower is born.
WHEN TO WATCH
The shower appears to originate in the Little Dipper, which is how it gets its name. The formal name of the Little Dipper is Ursa Minor, which translates as Little Bear. (Of course, some will argue it looks a lot more like a spoon.)
The shower will appear highest in the sky in the hours before sunrise on December 22, so set your alarm clock accordingly. The shower can produce around 10 meteors per hour, and to see them, all you’ll need is to find a place with no light and look up.
Moser suggests that you keep a thermos of hot chocolate in your hands and your phone in your pocket. "You'll see more meteors if you let your eyes adjust to the dark," she says. "As soon as you look at a bright light source like your phone, you have to start the adjustment process all over again! And hot chocolate will keep you warm and awake while patiently braving the cold December weather."
The Ursids have had some pretty spectacular showings—most notably in 1986, with spikes on the order of 100 meteors per hour. Don't get your hopes up for a wild display in 2016, however. Rather, appreciate the Ursids for what they are: an annual tradition of rare and romantic shooting stars in a beautiful, wintry, night sky. Enjoy the last big meteor shower of the year, and if it convinces someone to gift you a telescope, get ready: There are some astounding celestial wonders waiting for us in the new year.