Astronomers Finally Found the Origin of the Strangest Meteor Shower

In a strange twist, Earth passes through asteroid debris, and not comet leftovers, to create Geminid “shooting stars.”

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Photo taken on Dec. 14, 2021 shows a meteor of Geminids meteor shower at the Yulong Snow Mountain in...
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The Geminids, one of the most ample meteor showers of the year, is both bright and weird.

Every December, when Earth stumbles across the field of space debris strewn out across the orbit of 3200 Phaethon, bits and pieces slam into the atmosphere. Most showers are a byproduct of comets, which slough off gas as they approach the warmth of the Sun. The gas then strips the comet of dust and ice, and after enough trips around the star, the orbit is filled with this litter. Unlike the parent body of most meteor showers, 3200 Phaethon is an asteroid, making it an enigma.

Planetary scientists have been trying to decode why Phaethon acts so much like a comet, and hence why the Geminids are so strange. The show, while enchanting and a balm to our anxieties, probably stems from chaos. This revelation is detailed in a new paper published Thursday in the Planetary Science Journal.

The Geminids have strange origins

Asteroids are not the norm for showers. Most comets give off a bunch of debris as they approach the Sun, but asteroids are made of rocks and metals, so they behave differently. According to a description of the new work, most observations into the Geminids comes from observatories on the ground, which has made understanding them difficult.

Enter NASA’s Parker Solar Probe, a relatively young mission that has sojourned closer to the Sun than any other mission in history. As the spacecraft gets pelted with dust from the inner Solar System, it takes data of the barrage. These observations then help astronomers form models about how stuff moves around in the Solar System.

Using observations from Parker, Princeton University undergraduate student Wolf Cukier (who at 17 discovered an exoplanet) and collaborators found that Phaethon wasn’t any sort of comet in disguise. Instead, it’s shedding debris due to a collision between Phaethon and another object which struck it at a high velocity. This left the asteroid with more debris than usual to shed. In turn, some of this debris entered into an elliptical orbit around the Sun, which the Earth crosses into each year.

Based on the Parker observations, Cukier and Jamey Szalay — who had previously analyzed the cloud of dust — looked into if Phaethon was behaving more like a comet, or if a violent event led to the debris trail. Two models of chaos and one model of cometary behavior later, and the duo found that what Parker learned about dust behavior most closely resembled the team’s most violent scenario, helping solve a firey Solar System mystery.

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