The Unusual Source of the Geminids: An Asteroid with Baffling Behavior

Published by Adrien - 16 days ago
Source: Astronomy and Astrophysics

In a recent study accepted for publication in the journal Astronomy and Astrophysics, researchers have proposed a new origin for the Geminid meteor shower, a celestial phenomenon that dazzles the night sky at the end of each year. Unlike other meteor showers, the Geminids originate not from a comet, but from an asteroid named 3200 Phaethon. This discovery challenges previous estimates on the age of these meteorites, suggesting they could be nearly ten times older than previously thought.

Unlike other meteor showers that stem from comets, the Geminids are produced by the asteroid 3200 Phaethon, seen here in an artist's illustration.
Credit: NASA/JPL-Caltech/IPAC

The Geminid meteor shower gets its name from the constellation Gemini, from which the meteors appear to spring. However, their true origin is the asteroid 3200 Phaethon, a celestial body that follows an orbit bringing it close to the Sun at only 0.14 astronomical units, nearly one-tenth the distance between the Earth and the Sun. At this point in its orbit, Phaethon acquires a tail similar to that of a comet, made not of rocky fragments, but of much smaller particles, possibly of vaporized sodium.

The traditional theory that the Geminid fragments were deposited on an orbit intersecting Earth approximately 2,000 years ago is challenged by this study. The researchers explored the mechanism of rotational instability. This process implies that solar radiation pushes the asteroid, causing a gradual acceleration of its rotation until the centrifugal forces exceed gravitational forces, partially fragmenting Phaethon and thus creating the millions of rock pieces that could be the Geminids.

To support their theory, the researchers conducted simulations going back 100,000 years to trace the position and speed of Phaethon. They discovered that the asteroid, having become hyper-rotative, could have ejected the particles responsible for the Geminids 18,000 years ago. These simulations also suggest that only a fraction of these fragments was diverted toward us by the combined gravity of Venus and Earth about 4,000 years ago.

This discovery is not only fascinating for understanding the origin of the Geminids; it also paves the way for future missions, such as Japan's DESTINY+ mission, aiming to explore Phaethon and confirm the theory of rotational instability. Moreover, recent observations indicate that Phaethon is accelerating its rotation again, hinting at the birth of meteors in thousands of years.
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