Simulations of the peculiar asteroid Phaethon propose that the Geminid meteors could be much older than believed, possibly 10 times their previous estimation.
Recent research indicates that around 18,000 years ago, Phaethon, resembling a comet, ejected numerous rocky fragments towards Earth as it swiftly orbited the Sun, suggesting a chaotic event that may have aged the meteoroids beyond previous assumptions.
This photo taken late December 14, 2018 with a long time exposure shows a meteor streaking through the night sky over Myanmar during the Geminid meteor shower seen from Wundwin township near Mandalay city.
Insights from 3200 Phaethon and Rotational Instability
The Geminid meteor shower derives its name from the Gemini constellation, the apparent source of meteors. In reality, these meteors originate from the peculiar blue asteroid 3200 Phaethon, following a distinctive watermelon-shaped orbit that brings it within 0.14 astronomical units of the sun. At this point, Phaethon acquires a comet-like tail, challenging traditional views on the Geminid formation.
While astronomers long believed the tail comprised rock fragments responsible for the Geminids, recent observations indicate particles a thousand times smaller and potentially vaporized sodium. This discovery suggests the cloud of rocks forming the Geminid meteors must have originated in the past, raising questions about the timing and mechanism of their formation.
One theory proposes Phaethon deposited Geminid fragments around 2,000 years ago during its closest approach to the Sun. However, this theory faces challenges regarding the asteroid's need for massive ice content, prompting a focus on rotational instability as an alternative mechanism. According to this theory, solar radiation induces rotational acceleration, leading to centrifugal forces overcoming gravitational forces, fragmenting the asteroid over millions of years.
To test this hypothesis, researchers simulated Phaethon's behavior over the past 100,000 years, identifying nine 1,000-year periods for simulations. The results suggested that a rapidly spinning Phaethon could have produced the Geminids, with simulations aligning with observed trajectories.
The mass-shedding event occurred approximately 18,000 years ago, producing fragments diverted toward Earth by the gravitational pulls of Venus and Earth around 4,000 years ago.
The researchers anticipate confirmation of their findings through Japan's Phaethon-bound DESTINY+ mission, scheduled for launch in 2025. While Phaethon likely slowed down after shedding mass, recent observations indicate a renewed acceleration, suggesting the potential for future Geminid meteor births millions of years from now.
Geminid Meteor Shower 2024
The highly anticipated Geminid meteor shower is anticipated to reach its peak on December 13, 2024. Renowned for their reliability, Geminid meteors are most visible around 2 a.m. local time from dark-sky locations, although sightings are not limited to late evening hours.
This year, a luminous waxing gibbous moon will illuminate the night sky during the peak, providing moonlit conditions for observing the meteor shower.
Geminid meteors are known for their bold, white, and swift characteristics. Unlike those originating from comets, Geminids, derived from an asteroid, often consist of rock-sized pieces, resulting in bright flashes without persistent trails as they burn up in the Earth's atmosphere.
Astronomer Guy Ottewell explains that these meteors follow the asteroid's orbit, crossing Earth's orbit almost sideways from slightly to the front and slightly to the north. The radiant point, where meteors appear to radiate, is situated near Castor in the Gemini constellation and is highest in the sky around 2 a.m. during the long northern winter night.
Although the zenithal hourly rate for the Geminid shower is 120, observers may witness around 50 or more meteors per hour on a dark night near its peak. In optimal conditions, more than 120 meteors per hour are possible.
Given the moonlit skies in 2024, brighter meteors are likely to dominate the display. The Geminid meteor shower primarily favors the Northern Hemisphere but remains visible from the Southern Hemisphere as well.
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