Every year, astronomers watch the spectacle of the Geminids moving across the night sky from mid-November to late December. However, this meteor shower is very unusual, not least because it is one of the easiest to see.
Meteor showers usually come from comets that fly close to the Sun. Comets are made of cold gas, dust, and rock, and the Sun’s heat vaporizes some of the gas and expels it into the atmosphere, removing debris that eventually falls to Earth. But the Geminids are unique because they come from an asteroid instead of a comet. Asteroid 3200 Phaeton is the source of this debris, but asteroids are not affected by solar radiation in the same way as comets, so it is unclear why Phaeton left behind debris.
NASA scientists who analyzed data from the space agency’s Parker Solar Probe have now found a possible answer to the mystery of how the Geminids formed: a catastrophic event. “The Geminids may have formed the most brutal, devastating bodies that pass near the Sun,” scientists said in a study recently published in The Planetary Science Journal..
In pieces
So how did the Parker Solar Probe, designed to study the Sun, suggest how the Geminids were born? Its orbit passes between the Geminids at perihelion, or where they and 3200 Phaeton are closest to the Sun. As it flew through the meteor shower, Parker was hit by dust grains that gave off electrical energy. These signals were detected by his FIELDS instrument, which is designed to measure (among other things) electricity and magnetism. How fast the dust grains traveled and how hard they hit gave—an indication of how much—an idea of what might have caused the Geminids to form.
Parker’s data, together with the simulations of the Earth’s events, confirmed the scientific team, led by the planetary scientist Wolf Cuvier, that the Geminids did not leave 3200 Phaeton regularly. Phaeton and the debris that came from it could have been destroyed by a collision or explosion that broke up a much larger body, perhaps a comet. Cuvier and his team think it’s also possible that the same collision also created two neighboring asteroids.
Such collisions may also explain another mystery: the number of Geminids. Together, they are very large and may be larger than their parent asteroid. 3200 Phaeton loses some material in orbit, but not enough to account for the number of Geminids.
“The mass of the Geminids river is expected to be as large or larger than that of the parent group 3200 Phaethon, which indicates that the river was formed in a catastrophic way that shed a lot of mass in a short time. About 2,000 years ago,” the scientists also said in the study.
Terrible
Cuvier’s team used Parker’s data to find models of how the Geminids might form. Based on the results of the particles that fell in the research, they conducted several dangerous experiments. The first model simulated the catastrophic event of an asteroid strike; the second involved more violent events that would have scattered fast-moving debris over a large area. A third model controlled the formation of a meteor shower from a comet.
It turned out that the events were probably very violent, and this was supported by observations of the Geminids from Earth. Could such a crushing event have caused space rocks to fall to Earth thousands of years ago? Despite the threat, this could not be done. None of the three models showed any debris that has hit our planet.
Although Parker’s FIELDS tool is complex, there are some things it cannot tell us. The type of disaster that created the Geminids is still unknown. Whether it was a collision or an explosion would have affected the shape and width of the debris stream. Although Parker can’t directly explain the design, some missions will. JAXA’s upcoming DESTINY+ mission will aim directly at 3200 Phaeton after its launch in 2024. It may explain more about how the Geminids came to be by direct observation. Until then, we will look at the winter sky and wonder.
Planetary Science Journal, 2023. DOI: 10.3847/PSJ/acd538 (About DOIs).
Elizabeth Rayne is a creature that writes. His work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. When he’s not writing, he can move, draw, or play like someone no one has ever heard of. Follow him on Twitter @quothravenrayne.
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