The beautiful Geminids meteor shower is due to light up the heavens at its peak in a few days, but the source of the enigmatic cosmic display “Phaethon” had eluded stargazers for more than 120 years.
Although the popular astronomical event has been observed since the 1800s, its origins had long remained a mystery. It was only discovered relatively recently, compared to other showers such as the Perseids, which were first documented in 36 AD and Leonids, which date back to 902 AD.
Then, in 1983, two University of Leicester astronomers — Dr. Simon Green and Dr. John Davies — were studying data from the infrared sensitive telescope on the Infrared Astronomical Satellite, IRAS, and discovered an asteroid with a very unusual orbit.
Originally designated 1983 TB, the comet was renamed 3200 Phaethon after the son of Greek Sun god Helios — an appropriate moniker as it orbits closer to the Sun than any other asteroid then known.
Shortly after the find, Harvard astronomer Fred Whipple was able to link the newly discovered rocky object, which is about three miles wide, with the Geminid meteors, and the mystifying source of the showers was revealed.
Phaethon is small, only about 3 miles across, and it loops around the Sun every 1.4 years in an orbit that approaches the Sun closer than any other known asteroid. Researchers think Phaethon is a “rock comet” that sheds dusty debris each time it nears the Sun, when its surface fries to roughly 1,300°F (700°C) and rocky minerals on its surface crack, pop, sizzle, and fly off into space.
Over the centuries, these bits of Phaethon have spread all along the asteroid’s orbit to form a sparse, moving “river of rubble” that Earth passes through in mid-December each year. The particles are traveling 22 miles per second (79,000 mph) with respect to Earth at the place in space where we encounter them. So when one of them dives into Earth’s upper atmosphere, about 50 to 80 miles up, air friction vaporizes it in a quick, white-hot streak.