As an asteroid drifts through the vast emptiness of outer space, it begins to feel the tug of Earth’s gravity. Slowly drawn by the pull, the weight of invisible forces overpower it as its distance from the Earth’s orbit dwindles.
The asteroid 2024 PT5, also known as the “mini-moon,” orbited the planet from Sept. 29 to Nov. 24, according to Baylor University. About 10 meters wide, 1.5 million kilometers from Earth while moving at 3,500 km/h—these special factors led to the asteroid’s capture by Earth’s gravitational field.
“It’s just unique in the fact that it happened to be at a very specific speed and direction that it got caught up in orbit,” physics teacher Eric Cohen said. “But it’s just kind of a random asteroid that happened to be coming through.”
Much of the solar system is occupied by leftover debris from its formation, which are categorized as asteroids and comets. According to George Mason University associate professor of physics and astronomy Peter Plavchan, Ph.D., this mini-moon is considered an Apollo asteroid, which is part of a group of asteroids that are generally found orbiting in between Mars and Jupiter. Most asteroids don’t reflect enough sunlight to be visible to the human eye or regular telescopes when they’re out in the orbit of other terrestrial planets. Despite this object being noticed after entering Earth’s orbit, it is still only visible using professional equipment.
“As our ability to spot these smaller and smaller things get better and better, we will see it more and more often,” geosystems teacher Joshua Cooper said. “Being able to track its orbital path in action improves our model for how these space bodies react in non-gravity environments so we can better predict and see what might be a problem asteroid in the future.”
Asteroid 2024 PT5 was first observed on Aug. 7 by the Sutherland, South Africa telescope of the University of Hawai’i’s Asteroid Terrestrial-impact Last Alert System, according to the National Aeronautics and Space Administration (NASA). Astrological organizations and observatories nationwide will continue to observe this object as they anticipate its possible return to Earth’s orbit in the future.
“Astronomers are exploiting the fact that our universe and our solar system change in time,” Plavchan said. “By watching the sky all the time, we can start seeing things that happen rarely, like an Apollo asteroid that comes really close to the Earth.”
According to the California Institute of Technology, many projects focused on characterizing and cataloging near-Earth objects (NEOs) are responsible for the discovery of a significant number of asteroids. These findings can result in significant benefits for astronomical research worldwide, asteroid 2024 PT5 being no exception.
“Any sort of sample or information [researchers] can get gives a glimpse of things that are happening very far away from us, which is difficult to do, so it’s helpful that way,” Cohen said.
The collection of data from NEOs has also grown in the past decades. In 2005, Congress passed the NASA Authorization Act, mandating a survey program to detect NEOs and assess their threat to Earth. While threats have been identified over time, this mini-moon is not categorized as a danger due to its small size, short distance from man-made objects and low speed. However, the observation of harmless asteroids can still reveal significant undiscovered information about outer space.
“Studying our solar system helps us compare what we’re seeing around these more distant worlds where we have less information,” Plavchan said. “We can kind of use our solar system as an analogy. It turns out it’s not great, though. Turns out solar systems like ours are actually rare and the more common types of solar systems are different from ours.”
Researching NEOs can sometimes lead to more data about faraway worlds. Large space debris even contain the possibility of evidence of life and its origin. The Earth’s temporary second moon and other fragments of the solar system’s history that might come across this planet continue to contribute to astronomers’ understanding of Earth’s place in the solar system.
“[Asteroid 2024 PT5] will be back around in 2050, so it’s gonna be within your lifetimes,” Cooper said. “It got kind of hyped up as our ‘mini-moon,’ but this is gonna happen quite often.”
