The true origin of Geminid stones, one of the most beautiful meteor showers

Every year, around mid-December, a meteor shower can be enjoyed in the constellation Gemini: Gemini, which generally marks the peak of activity during the night of December 13 to 14. Depending on the year, it is possible to observe up to a hundred meteors per hour – although it is essential to choose a location that is as free of them as possible. Light pollutionLight pollution. Shooting stars are not stars in the strict sense of the word, but small meteorites – fragments of cosmic dust, which upon entering spaceAtmosphereAtmosphereLight trail production.

What are stars? Franck Menent explains it all to you in this episode of Futura dans les Étoiles. © Futura

Phaethon, the mother body of the Geminids

Scientists have long suspected that the Geminid swarm came from the asteroid Phaethon, due to its presence OrbitsOrbits Communities. However, meteor swarms generally come from comets approaching Earth sunsunpartially sublimated, producing streaks GasGas And dust that could later cross Earth's orbit. Many scholars assume this Tourist carTourist car It will actually be what's left of the core CometComet. When the object reaches its closest approach to the Sun (at a distance of about one-tenth of the Sun's distance from Earth), it also forms a thin tail, much like the tail of a comet.

Astronomers have long believed that this tail consisted of fragments of the rock that would have given birth to Gemini. However, recent observations seem to contradict this hypothesis, suggesting that the tail's current particles are up to a thousand times smaller than those of Gemini's rocks: hence, cloudsclouds The rocks responsible for Gemini's formation were likely formed in the past. One theory suggests that Phaethon deposited Geminid fragments near Earth about 2,000 years ago, because that's when the object passed close to the Sun. But according to a new study, if Phaethon had produced Gemini via Due to cometary activity, the asteroid should have contained massive amounts of ice to eject these fragments…which seems unlikely according to Digital modelsDigital models. To explain the origin of the gemini, the authors looked to another mechanism: Phaeton rotational instability. They present their work in the magazine Astronomy and astrophysics.

The Geminids are actually much older than we thought!

According to the authors, the phenomenon of rotational instability occurs when… Solar radiationSolar radiation It would “push” an asteroid, gradually accelerating it Rotation speedRotation speed So that after a few million years, it rotates fast enough to Gravitational forcesGravitational forcesWhich carries the components of the asteroid AgglomerationsAgglomerations Between them, they see themselves as superior to Centrifugal forcesCentrifugal forces. In the case of Phaethon, this instability could cause it to partially break up, creating millions of pieces of rock and dust… and possibly Geminids.

And the Digital simulationDigital simulation Scientists seem to support this hypothesis. Even better, two of his simulations perfectly mimic the observed paths of the Geminids! Their models thus indicate that the Phaeton would have suffered a significant loss MassMass Due to the instability of its rotation about 18 thousand years ago, which, according to scientists, led to the production of a cloud of particles responsible for the emergence of Gemini. After losing mass, the authors suspect that Phaethon's rotation gradually slowed down, due to its motion being preserved. Angular momentumAngular momentum ; But recent observations indicate that its rotation speed is increasing again, shortening its rotation period Rotation periodRotation period Four milliseconds every year. So new meteorites could see the light of day… within a few million years.