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When we glance up at the night sky, our eyes often fall upon the moon, Earth's companion for more than 4 billion years. But picture our planet temporarily having a much smaller satellite. Say hello to 2024 PT5, an asteroid which will be turning Earth's temporary mini-moon between September 29 and November 25, 2024.
What exactly is a Mini Moon
Recently, there's been a great deal of excitement around the prospect of Earth receiving a 'mini-moon', and understandably, you're probably wondering what this means. A mini-moon is an asteroid that gets trapped by Earth's gravity and orbits our planet for a period of time before escaping back into space.
During these rare events, the asteroid is also likely to be very small and difficult to detect. The upcoming mini-moon 2024 PT5 was detected with the Asteroid Terrestrial-impact Last Alert System known as ATLAS. Because of their very small size and rapid mobility, continuous monitoring of these asteroids is both difficult and resource intensive.
Earth has had mini-moons in the past
The last known mini-moon was 2020 CD3, which orbited Earth from 2018 to 2020. This mini moon was discovered in February 2020, about the size of a car, and followed a chaotic orbit around our planet before escaping back into space. By contrast, our next mini-moon (2024 PT5) will be in Earth's orbit from September 29 until November 25, 2024, for just two months. Both mini-moons are about the same size and too tiny to be seen with the naked eye, but 2024 PT5 will travel in a more predictable horseshoe-shaped orbit that should provide scientists with a better opportunity for exploration.
Earth's second Moon
Scientific models proposed by Erik Asphaug and Martin Jutzi in 2011 suggest that Earth may have had two moons in its distant past. Their research indicates that 4.5 billion years ago. Models suggest the the two moons co-existed, orbiting Earth for around 80 million years before second moon purportedly impacted with our current Moon.
The resulting impact of our two moons would have ejected trillions of tons of space debris into Earths orbit, some of it crashing down onto the surface of the planet. This celestial event would also solve the mystery of the moons rough and mountainous dark side that juxtaposes its relatively smooth Earth facing side.
Can you Observe a Mini Moon?
Unfortunately, finding a mini-moon like the 2024 PT5 requires a telescope with at least 30-inch diameter and high-sensitivity detectors, normally readily available at professional observatories. According to Carlos de la Fuente Marcos, a Universidad Complutense de Madrid professor, "even the most powerful amateur telescopes won't catch a glimpse of 2024 PT5."
As we’re approaching the end of September, look up to the stars, knowing that while you perhaps are not seeing 2024 PT5, there is a companion fleetingly along the journey in our space.