A spectacular meteor shower has an origin story in a “violent and cataclysmic event,” suggests a new study.
Meteor showers usually come from comets, icy bodies sometimes called “dirty snowballs” that circle the solar system. The Geminids meteor shower, or Geminids, however, comes from an asteroid or space rock known as 3200 Phaethon. Every December, Earth passes through the stream of dust left behind by Phaethon and the tiny specks provide a light show high in the atmosphere.
The Geminids, one of the year’s best, likely arose after 3200 Phaethon suffered “a high-speed collision with another body or a gaseous explosion, among other possibilities,” NASA officials wrote Wednesday ( June 14).
NASA’s Parker Solar Probe mission, which usually looks at the sun up close, has provided the keystone evidence showing how the intense meteor shower occurred.
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“It is unusual that this [shower] it appears to come from an asteroid,” said Wolf Cukier, a young man at Princeton University who led the research, in a university statement. The dust stream also has a quirk: It circles the sun slightly outside Phaethon’s orbit , based on another recent study with Parker images of the Geminids led by Karl Battams of the Naval Research Laboratory.
Rocks are usually unaffected by heat when flying Phaethon’s distance from the sun, even if it enters the orbit of Mercury. This physics problem creates a puzzle for astronomers. “As it flies close to the sun, it appears to have some sort of temperature-driven activity. Most asteroids don’t,” said Jamey Szalay, a researcher at Princeton and co-author of the study, in the NASA statement.
Szalay is also a guest investigator on Parker, which periodically swings extremely close to the sun to observe the origin of the solar wind and the resulting space weather (auroras and magnetic activity) that its charged particles generate high in Earth’s atmosphere.
The sun, because it has a large gravity well, attracts many comets and asteroids that pass by it. Parker thus ends up being useful for observing the specks of dust that these small bodies leave behind and shedding light on where they come from.
Parker is not designed to count or characterize dust particles, as there are no such instruments on board. That said, he is constantly hit by bits of dust that create electrical signals.
The resulting small puffs of charged gas, or clouds of plasma, generate information that the spacecraft’s Fields suite of instruments can see. (Fields is designed to examine electrical and magnetic events generated by the sun, but it’s sensitive enough to detect the tiny explosions each speck of dust creates on Parker.)
In the study, Cukier and Szalay modeled the formation of the dust stream left behind by 3200 Phaethon, based on Parker’s data. They considered a variety of scenarios, ranging from less violent ones (the dust gradually moves away from the asteroid) to a more violent departure caused by a collision or explosion (which causes the dust to have a relative speed of 0.6 mph or 1 km/ha Phaethon).
The three models they produced showed that the dust stream probably formed from the most violent of scenarios, as that prediction most closely matched what Parker observed in space.
Cukier, who is graduating this year, added that he has always been drawn to the sky and that learning about the Geminids requires only looking up. “Planetary science is surprisingly accessible,” he said.
A study based on the research was published today (June 15) in the Planetary Science Journal.
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