Geminid meteors could be 10 times older than previously believed, a new study suggests

The origin of the majestic Geminid meteor shower some 18,000 years ago has been a chaotic one, a new study suggests. If this is found to be true, then Geminid meteoroids are about 10 times older than previously estimated.

The Geminid meteor shower takes its name from the constellation Gemini, where the meteors appear to originate in the sky. However, these meteors stem from 3200 Phaethon, an unusual blue asteroid following an orbit shaped like a watermelon's path. This asteroid comes remarkably close to the sun, reaching just 0.14 astronomical units away, approximately one-tenth of the Earth's distance form Sun.

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During this phase of its orbit, Phaethon, measuring 3.2 miles wide (5.1 kilometres), develops a distinct comet-like tail.

For years, astronomers believed that the tail was composed of rock fragments that form the dust cloud that in turn generates the Geminids. But as per the recent study, the tail’s present-day particles are a thousand times smaller than the Geminids’ head-size rock, which contradicts the previous theory.

Some recent observations also suggest that these present-day tail particles may be made of vaporised sodium and not dust. Hence, the cloud of rock responsible for the Geminid meteor must have formed way earlier than it was thought.

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Geminids are much older than previously thought

Hangbin Jo, a graduate student at Korea’s Seoul National University and co-author Masateru Ishiguro, a professor in astronomy at the same university went on to produce some theories to find out the Geminids’ exact timeline. They came up with a mechanism called rotational instability.

Jo explained that during this process, solar radiation would exert a "push" on the asteroid, leading to a gradual acceleration of its rotation. This continuous acceleration over millions of years would eventually cause the asteroid to spin rapidly enough for centrifugal forces to surpass the gravitational forces holding its smallest components together.

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In the case of Phaethon, this instability would result in partial fragmentation, giving rise to millions of gravel pieces, and potentially forming the Geminid meteor shower.

Their research has been accepted for publication in the journal Astronomy and Astrophysics.

To validate their hypothesis, the researchers conducted a reverse analysis starting from the current day, calculating Phaethon's position and velocity over the past 100,000 years. Subsequently, they selected nine consecutive time intervals, each spanning 1,000 years, during which they simulated the asteroid ejecting rock fragments.

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The simulations revealed that a super-spinning Phaethon could have produced the Geminids. For one, their results suggested that the meteors' total mass would average 10 million tons. Moreover, two simulations almost exactly mimicked the Geminids' observed trajectories.

In these models, Phaethon's mass-shedding occurred 18,000 years ago, leading the researchers to conclude this was when the particles responsible for the Geminids were likely cast into space.

(With inputs from agencies)