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The Gemini meteor shower that lights up the skies each December is one of the most active and reliable celestial displays of the year.
However, the actual origins of the winter light show are a mystery. Now astronomers using NASA’s Parker Solar Probe have gained more insight into Gemini’s underlying cause.
The meteor shower was first recorded in 1862 and appears to radiate from Gemini. In mid-December, when the meteor shower is at its peak, you can see 120 bright yellow meteors per hour if the sky is clear.
Meteors usually come from leftover bits and pieces of comets orbiting the sun. Comets originating from the icy outer reaches of the solar system shed particle trails as they passed close to the sun. Meteor showers appear in Earth’s skies as Earth passes through the debris trail. According to NASA, the particles burn and disintegrate as they collide with Earth’s atmosphere, leaving a burning trail.
However, Geminids are unusual in that they have been traced to the asteroid 3200 Phaethon. Scientists have debated what Phaethon might be. It is possible that Phaethon is a “dead comet” with an ice shell that eventually melted. Near-Earth asteroids that track closely are likened to comets and are called “rock comets.”
“The really strange thing is that we know that Phaethon is an asteroid, but it seems to have some sort of temperature-driven activity as it flies next to the sun. Most asteroids don’t do that. Szalay is a co-author of a study on asteroids published June 15 in The Planetary Science Journal.
Launched in 2018, the Parker Solar Probe is on a mission to “touch” the sun and study it, but the spacecraft’s increasingly closer approach to our star is useful for scientists trying to study the dust swirling around the inner solar system. The probe’s instruments gave scientists detailed information about dust particles shed by comets and asteroids as they traveled around the sun, and in doing so shed new light on the Geminids-Phaethon connection.
The spacecraft doesn’t actually carry a dust counter to measure the particles, but the particles do affect the Sun-orbiting Parker Solar Probe. When the dust hits the spacecraft, it creates electrical signals that the probe’s instruments can pick up, including those measuring the electric and magnetic fields near the sun.
Jiang Feibo/China News Service/VCG/Getty Images
A Gemini meteor shower crosses the night sky over the Lhasa River, Tibet, on December 14, 2022.
Data collected by the Parker Solar Probe was used by scientists to model three different scenarios for the Geminid meteor shower, which were then compared to models based on observations from Earth.
Data suggests that the most likely cause of a meteor shower is a sudden and violent event, likely a rapid collision of an asteroid with another space rock or even a gas explosion of the sort that caused Gemini to first appear in our skies in 1862.
Phaethon was discovered on October 11, 1983 by astronomers using infrared astronomical satellites.
After Phaethon’s discovery, astronomer Fred Whipple realized that asteroids and Gemini meteor shower streams had nearly identical trajectories and made a connection between the two.
It is the first asteroid associated with a meteor shower and has a diameter of about 5.10 km. Astronomers have been studying space rocks for years to figure out why they behave like comets.
The space rock is named after a Greek myth about the son of the sun god Helios.
Phaethon orbits closer to the Sun than any other asteroid and takes 1.4 years to complete an orbit.
Even before studying dust in our solar system with the Parker Solar Probe, astronomers confirmed that the asteroid heats up to about 1,300 degrees Fahrenheit (704 degrees Celsius) on its closest approach to the Sun, causing Phaethon to shed more dust debris.
These particles jump into Earth’s atmosphere at 79,000 miles per hour (127,000 kilometers per hour) each year, evaporating into streaks we call “shooting stars,” causing meteor showers.
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