The Geminids are one of the astronomical highlights of the year and provide a spectacular display of shooting stars every December. Scientists are now beginning to understand where they came from.

Scientists believe that something catastrophic happened at this time Asteroid named 3200 PhaethonThis causes it to crumble and throw pieces of debris into a long ring around the sun. Every year our own planet races through this cloud of debris, producing one of the most impressive meteor showers – the Geminids.

Look up on a clear night in mid-December and you might catch a glimpse of them – streaks of light streaking across our sky. These are particles from this asteroid that evaporate in our atmosphere Speeds of up to 79,000 miles per hour (127,000 km/h).

The Geminids are particularly notable for the variety of their colors, including yellow, green and blue, says Tomáš Henych, an astrophysicist at the Czech Academy of Sciences. They are also very bright, with up to 150 meteors visible to the naked eye hourly. “Usually you see beautiful meteors,” says Henych.

But the Geminids are unique for another reason: They are the only known meteor shower to originate from an asteroid. All others come from the Ice debris ejected by comets as the sun blasts material from their surfaces. Asteroids, which are mostly rock, typically don’t form tails in this way.

But in 1983, astronomers discovered 3200 Phaethon, a bluish asteroid This appeared to be about 3.6 miles (5.8 km) wide fit together closely The path of debris associated with Gemini, so named because they point toward the constellation Gemini in the sky. This discovery led to the likely conclusion that the meteor shower originated from this object. “That is very likely,” says Henych. This also explains why the Geminids have such a wide range of bright colors – the particles they produce “are harder,” says Henych, and contain a greater number of elements compared to those of comets.

Phaethon’s orbit around the sun is also “very unusual,” says Rhian Jones, a planetary scientist at the University of Manchester in the United Kingdom. “It comes very close to the sun, closer than Mercury,” she says, to about 0.14 times the distance between Earth and the sun. “So, it’s getting pretty hot,” up to about 750 °C (1,400F).

And this unusual orbit has given scientists some clues about how the Geminids were born.

In March 2024, amateur astronomer Danila Milanov in Russia and her colleagues modeled the path of meteor debris and the orbit of Phaethon today slightly separated by about 20,000 km (12,000 miles). This is what they found out 1,200 to 2,400 years ago the two seemed to overlap. However, Milanov says, “we suspect that a catastrophic event occurred on this time scale” that formed the meteors another study says the event may have occurred up to 18,000 years ago.

What exactly this event might have been is hotly debated. One possibility is that the asteroid collided with another object and broke apart. But Wolf Cukier, a graduate student in astronomy and astrophysics at the University of Chicago who has studied the Geminids, thinks this is unlikely because few asteroids are spotted near the sun. This suggests that there is a common mechanism that eliminates them and that asteroid collisions are rare. “They definitely can’t all be explained by collisions,” he says. It could be that the extreme heat near the Sun meant that few asteroids could survive. Phaethon seems to be an exception.

In fact, the preferred explanation for the Geminids is that Phaethon was moved toward the Sun from the asteroid belt, perhaps through gradual gravitational interactions with planets like Jupiter. Then, about 1,800 years ago, its orbit brought the asteroid so close to the sun that the heat caused it to break apart.

In 2023, Cukier data used from a NASA spacecraft called the Parker Solar Probe to learn more about this process. In 2020, Parker secretly observed another section of the Geminid debris stream in space. Based on these observations, Cukier concluded that the Geminids likely resulted from a single violent event and did not represent a continuous release of debris like a comet.

This event may have been a “low-velocity explosion,” says Cukier. “As asteroids approach the Sun, they become hot, and this causes thermal stress inside the asteroid. If they get too hot, that stress can build up to the point where the asteroid breaks up into many pieces.”

Another possibility is that the asteroid broke apart due to its rotation. Phaethon currently rotates once every 3.6 hours, which is “very fast,” says Qicheng Zhang, an astronomer at Lowell Observatory in Arizona, which may be due to the Sun heating its surface and giving it a rotation speed when receiving radiation flying off the surface, which is known as Yorp effect.

In 2023, Zhang observed the creation of sodium emitted by Phaethonthat could be related to this process. “It may have lost much of its surface area as parts of it were thrown off, exposing fresh sodium underneath,” he says.

An impending Japanese mission called Fate+which is scheduled to hit the market in 2028, could give us answers. The spaceship will Fly past Phaethonand takes pictures of its surface. If the idea of ​​rapid rotation is correct, “you would expect landslides and rocks flowing toward the equator, where centrifugal force should push things off,” Zhang says.

“Unraveling the mysterious origins of the Geminids will not only help us better understand a spectacular annual light show – it can also teach us more about the solar system as a whole,” says Minjae Kim, a planetary scientist at University College London in the UK. “It shows us that meteor showers can occur through different mechanisms,” says Kim. There are other asteroids It is also known to be quite close to the Sunsuggesting that we “may have to expect similar meteor showers to form in the future.”

Phaethon is expected to eventually fall into the Sun in about 10,000 years, Zhang says, leaving only the Geminids behind. At some point they too will be swept away by our star.

“Phaethon shows us how asteroids die,” says Zhang.

But for now it means we’re lucky to be just in time to see this meteor shower. “We happen to be at a point in time and space where Earth is flying through the Geminids,” says Cukier.

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