Collisions ahead
Each year, as our planet orbits the Sun, it passes through streams of tiny dust-size particles of rock and metal. Astronomers call these particles meteoroids when they are floating freely in space, but when they burn up in the atmosphere, they become meteors. If, by chance, they survive the fiery ordeal of passage through our thick blanket of air to land on the ground, they are then labeled meteorites. No meteorites come from meteor showers — the particles are too small.
Most meteor showers originate from comets. When a comet swings around the Sun, our star’s heat boils off ice from the surface and, with it, trapped dusty debris. When the orbit of the debris trail crosses Earth’s orbit, we experience a meteor shower. That said, the two exceptions to the comet rule are on this list: December’s Geminids originate with dust from the asteroid 3200 Phaethon. And January’s Quadrantids’ parent body is the near-Earth asteroid 196256, also known as 2003 EH1.
If you trace all the meteor trails from a particular shower backward, they meet within the boundaries of a constellation. Astronomers name all meteor showers for the constellations they appear to originate in. Trace all Leonids backward, and they’ll meet in Leo the Lion. The point of origin, which marks the direction in space toward which Earth is heading, is called the radiant.
OK, that rule seems fine until we get to the Quadrantids. After all, there’s no constellation whose name begins with Q. Ah, but there was. As late as the early 20th century, celestial mapmakers placed the constellation Quadrans Muralis (the Mural Quadrant) in the sky near Boötes. And because the meteor shower was named before the constellation became defunct, the shower is still the Quadrantids.
To help you get ready for 2020’s late-year fireworks, I’ll discuss the four major upcoming meteor showers. Please note that for each of these, you’ll see more meteors per hour after midnight. That’s when Earth has rotated enough so the observer’s location is heading into the meteoroid stream. Before midnight, the particles have to catch up to us to enter the atmosphere.