Asteroid 3200 Phaethon's thick trail of debris, which is the source of the annual Geminids meteor shower here on Earth, has a mass of about a billion tons, is 60,000 miles wide, and is more than 14 million miles long.
Scientists at America's Naval Research Laboratory (NRL) built a specialized camera known as the Wide-Field Imager for Solar Probe (WISPR) to study the solar wind and how space weather can disrupt GPS satellites and energy grids. The instrument, attached on top of NASA’s Parker Solar Probe, has revealed the elusive trail of dust left over from the space rock in unprecedented detail.
3200 Phaethon has a wildly eccentric orbit that brings it closer to the Sun than Mercury, and flings it back out further than Mars. Astronomers have detected the spray of debris emitted from the asteroid before. As the asteroid whips around, the dirt is compressed into a tail. Although the streak stretches long and wide, and collectively contains more than a billion tons of dirt, it’s difficult for telescopes to find – though when our home world passes through the debris, the material shows up as the Geminids meteor shower to us Earthlings.
The trail as a whole is best observed near the Sun; it’s believed that solar radiation pressure causes bits to break away from the asteroid, so when it's close to our star, more stuff is possibly knocked off the cosmic rock. But our star’s glare drowns out its presence making it hard for telescopes to see it.
“This is why NRL’s heliospheric imagers are so ground-breaking,” Karl Battams, a computational scientist at the NRL’s space science division, said on Wednesday. “They allow you to see near-Sun outflows massively fainter than the Sun itself, which would otherwise blind our cameras. And in this case, you can also see solar system objects extremely close to the Sun, which most telescopes cannot do.”
WISPR captured enough detailed data to allow researchers to estimate the size and mass of 3200 Phaethon’s dust trail. The sheer amount has led them to question the nature of the asteroid itself.
“There’s no way the asteroid is anywhere near active enough when it is near the Sun to produce the mass of dust we are seeing,” Battams said.
There must be something else other than solar radiation pressure that is making the space rock emit so much debris seen in the Geminids meteor shower, though the eggheads aren’t quite sure what exactly.
“Something catastrophic [must have] happened to Phaethon a couple of thousand years ago and created the Geminid Meteor shower,” he added.
WISPR takes snapshots in the visible light spectrum of the solar corona and solar outflow using two overlapping cameras. NASA’s Parker Solar Probe was launched in 2018 and is expected to continue orbiting our star, approaching as close as 4.3 million miles from its center, for another five years or so. ®