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Artist’s concept of the Parker Solar Probe spacecraft approaching the sun. Launched in 2018, the probe is increasing our ability to predict key space weather events that impact life on Earth. Credit: NASA/Johns Hopkins APL/Steve Gribben

Geminids meteoroids light up the sky as they hurtle past Earth each winter, producing one of the most intense meteor showers in our night sky.

The mysteries surrounding the origin of this meteoroid stream have long fascinated scientists because, while most meteor showers are created when a comet spews a tail of ice and dust, the Geminids derive from a chunk of rock from an asteroid. which does not normally produce a queue. Until recently, the Geminids had only been studied from Earth.

Now, Princeton researchers have used observations from NASA’s Parker Solar Probe mission to deduce that it was likely a violent, catastrophic event, such as a high-speed collision with another body or a gas explosion, that created the Geminids. The results, published in The planetary science journalnarrow down the hypotheses about the composition and history of this asteroid that would explain its unconventional behavior.

“Asteroids are like little time capsules in the formation of our solar system,” said Jamey Szalay, a researcher at Princeton University’s Space Physics Laboratory and co-author of the paper. “They formed when our solar system formed, and understanding their composition gives us another piece of the story.”

An unusual asteroid

Unlike most known meteor showers that come from comets, which are made of ice and dust, the Geminids stream appears to come from a chunk of rock and metal asteroid called 3200 Phaethon.

“Most meteoroid streams form through a cometary mechanism. It’s unusual for this to appear to come from an asteroid,” said Wolf Cukier, an undergraduate class of 2024 at Princeton and lead author on the paper.

“Also, the stream orbits slightly outside of its parent body when it’s closest to the sun, which isn’t obvious to explain just by looking at it,” he added, referring to a recent study with Parker Solar Probe images of the Geminids. led by Karl Battams of the Naval Research Laboratory.

As a comet travels close to the sun, it gets hotter, causing surface ice to release a tail of gas, which in turn carries small chunks of ice and dust with it. This material continues to trail the comet as it remains within the gravitational pull of the sun. Over time, this repeated process fills the parent body’s orbit with material to form a stream of meteoroids.

But because asteroids like 3200 Phaethon are made of rock and metal, they typically aren’t affected by the sun’s heat like comets are, leaving scientists to wonder what causes 3200 Phaethon’s flux to form in the night sky.

“What’s really weird is that we know 3200 Phaethon is an asteroid, but as it flies close to the sun, it appears to have some kind of temperature-driven activity,” Szalay said. “Most asteroids don’t do that.”

Some researchers have suggested that 3200 Phaethon may actually be a comet that has lost all of its snow, leaving only a rocky asteroid-like core. But new data from Parker Solar Probe show that although some of 3200 Phaethon’s activity is related to temperature, the creation of the Geminid stream likely wasn’t caused by a comet mechanism, but by something much more catastrophic.

Time capsule opening

To learn about the origin of the Geminids stream, Cukier and Szalay used new Parker Solar Probe data to model three possible formation scenarios, then compared these models to existing models created from ground-based observations.

“There are what’s called the ‘basic’ model of a meteoroid stream formation and the ‘violent’ model of creation,” Cukier said. “It’s called ‘basic’ because it’s the easiest thing to model, but in reality these processes are both violent, just different degrees of violence.”

These different models reflect the chain of events that would occur according to the laws of physics based on different scenarios. For example, Cukier used the basic model to simulate all the pieces of material released by the asteroid with zero relative velocity or no velocity or direction relative to 3200 Phaethon to see what the resulting orbit would look like and compare it to the orbit shown by the asteroid. Parker Solar Probe probe data.

He then used the violent creation model to simulate the release of material from the asteroid with relative speeds of up to one kilometer per hour, as if the pieces had been torn apart by a sudden and violent event.

He also simulated the comet model, the mechanism behind the formation of most meteoroid streams. The resulting simulated orbit looked less like how the orbit of the Geminids actually looks according to Parker Solar Probe data, so they ruled out this scenario.

By comparing the simulated orbits of each of the models, the team found that the violent patterns were most consistent with data from the Parker Solar Probe, meaning that a sudden, violent event such as a high-speed collision with another body is likely to or a gaseous explosion, among other possibilities, created the Geminid stream.

The Princeton researchers used observations from NASA’s Parker Solar Probe mission to infer that it was likely a violent, catastrophic event, such as a high-speed collision with another body or a gas explosion, that created the meteor stream. of the Geminids. Credit: NASA/Johns Hopkins APL/Ben Smith

The research builds on work by Szalay and several colleagues on the Parker Solar Probe mission, built and assembled at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, to assemble a picture of the structure and behavior of the large solar cloud. dust swirling through the inner solar system.

They took advantage of Parker’s flight pathan orbit that swings it just millions of miles from the sun, closer than any other spacecraft in history, to get the best direct look at the dusty cloud of specks released by passing comets and asteroids.

While the spacecraft doesn’t measure dust particles directly, it can track dust grains intelligently: As dust grains strike the spacecraft along its path, high-velocity impacts create clouds of plasma. These impact clouds produce unique signals in the electric potential that are picked up by several sensors on the spacecraft’s FIELDS instrument, designed to measure electric and magnetic fields near the sun.

“The first-of-its-kind data our spacecraft is collecting now will be analyzed for decades to come,” said Nour Raouafi, Parker Solar Probe project scientist at APL. “And it’s exciting to see scientists of all levels and abilities digging into it to shed light on the sun, the solar system, and the universe beyond.”

Reach for the stars

Cukier said his passion for learning about space, combined with the support from the department, is what motivated him to pursue this project.

After taking a hands-on laboratory course offered by the Princeton Space Physics Laboratory, where he gained hands-on experience building space instruments, such as those currently sampling the sun’s environment aboard the Parker Solar Probe, and serving as treasurer for the club of university astronomy, he decided he wanted to continue his extracurricular research studies.

He was greeted with enthusiasm when he contacted scientists from the Princeton Space Physics group. “Everyone is very supportive of university research, especially in astrophysics, because it’s really part of the departmental culture,” he said.

“It’s always wonderful when our students like Wolf can contribute so strongly to this kind of space research,” said David McComas, head of the Space Physics group and vice president of the Princeton Plasma Physics Laboratory (PPPL). “Many of us have admired the Geminids meteoric displays for years and it’s great to finally have the data and research to show how they were likely formed.”

Cukier said he has been drawn to observing the sky since he was a child. “Planetary science is surprisingly accessible,” he said. “For the Geminids, for example, anyone can go out at night on December 14 this year and look up. It’s visible from Princeton and some of the meteors are really bright. I highly recommend seeing it.”

More information:
WZ Cukier et al, Formation, structure and detectability of the Geminids meteor stream, The planetary science journal (2023). DOI: 10.3847/PSJ/acd538

About the magazine:
The planetary science journal

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