Geminids Meteor Shower Origin Demystified

Millions of people watch the Geminids meteor shower every year. This intense event usually peaks around December 13th or 14th and appears to originate from the Gemini constellation, giving them their name. The Geminids are one of two meteor showers that do not originate from a comet.

Most meteor showers come from a comet’s tail of ice and dust. The Geminids and Quadrantids stem from an asteroid. Specifically, the Geminids come from an asteroid called 3200 Phaethon, a chunk of rock and metal with the distinction of orbiting closer to the Sun than any other named asteroid.

Princeton researchers have taken the typically earthbound research into space, using observations from NASA’s Parker Solar Probe mission to determine that the Geminids came into being from what was likely a violent, catastrophic event like a high-speed collision or gaseous explosion.

“Asteroids are like little time capsules for the formation of our solar system,” said Jamey Szalay, a research scholar at the Princeton University space physics laboratory and co-author of the paper. “They were formed when our solar system was formed, and understanding their composition gives us another piece of the story.” 

As comets move closer to the Sun, the heat causes the ice on its surface to release a tail of gas, ice, and dust. Over time, the comet’s orbit fills out, creating material for a meteoroid stream. Asteroids, however, are rock and metal and aren’t typically affected by the Sun’s heat like comets. This leaves scientists wondering what causes 3200 Phaethon’s meteor stream, which orbits slightly outside the asteroid’s body.

“What’s really weird is that we know that 3200 Phaethon is an asteroid, but as it flies by the Sun, it seems to have some kind of temperature-driven activity,” Szalay said. “Most asteroids don’t do that.” 

Some researchers have suggested that 3200 Phaethon may have been a comet, but it has lost the snow and ice on its surface, leaving only a rocky core resembling an asteroid. However, the new Parker Solar Probe data shows that, while some of 3200 Phaethon’s activity is temperature based, the Geminids’ creation was more catastrophic.

The Geminids meteor shower will occur from November 19th through December 24th this year, peaking on the 13th, 14th, and 15th of December. While most visible in the northern hemisphere, those in the southern hemisphere can also see them at a reduced rate.

They published their findings in the Planetary Science Journal on June 15th.