Earth’s Temporary Mini-Moon to Orbit Next Week

Next week, Earth will temporarily gain a second moon as a small asteroid, known as 2024 PT5, enters its orbit. This tiny space rock, recently discovered by NASA-funded scientists, will circle our planet for around two months. However, due to its size, the so-called “mini-moon” will not be visible to the naked eye, and even most standard telescopes will fail to capture its presence. Advanced observational tools are necessary to witness this rare celestial event.

On August 7, 2024, scientists identified asteroid 2024 PT5 using the Asteroid Terrestrial-impact Last Alert System (ATLAS) in South Africa. This system regularly monitors near-Earth objects, providing alerts for potential impacts. During one of these routine checks, the researchers discovered 2024 PT5, which is believed to have originated from the Arjuna asteroid belt. This belt, located approximately 93 million miles away, contains asteroids that follow Earth-like orbits around the sun. Next week, this asteroid will briefly join the Moon as a second companion to Earth, marking a rare occurrence in space.

Asteroids like 2024 PT5 that enter Earth’s gravitational field can be classified as “mini-moons.” Rather than flying past or colliding with Earth like many other space rocks, mini-moons get temporarily captured in Earth’s orbit. They remain there for a short period before continuing their journey through space. Standing about 33 feet long—roughly the size of a bus—2024 PT5 will circle Earth in a horseshoe-shaped orbit from September 29 to November 25. It will not complete a full revolution around the planet, but instead will trace an arc-like path. The asteroid is expected to make its closest approach in January 2025 before leaving Earth’s vicinity, and it may return to our orbit in 2055.

To qualify as a mini-moon, certain conditions must be met. According to Carlos de la Fuente Marcos, lead author of the study and professor at the Universidad Complutense de Madrid, a mini-moon must approach within 2.8 million miles of Earth and travel at a speed of approximately 2,200 miles per hour. Only objects that meet these parameters can be temporarily captured by Earth’s gravity. Although 2024 PT5 satisfies these conditions, it remains an extremely rare case. In fact, there have been very few confirmed mini-moons in recorded history, making this event particularly special for astronomers.

Despite the excitement surrounding Earth’s temporary second moon, asteroid 2024 PT5 will not be visible without specialized equipment. Its small size and dimness mean it will go unseen by the naked eye. Even amateur telescopes and binoculars will struggle to pick it up. De la Fuente Marcos explains that only professional-grade telescopes with at least a 30-inch diameter, along with advanced detection systems such as charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor detectors (CMOS), will be able to spot the asteroid. For most people, this mini-moon will remain an invisible phenomenon.

One intriguing possibility is that asteroid 2024 PT5 may actually be a piece of Earth’s own Moon. Paul Chodas, director of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory, suggests that the asteroid’s motion and trajectory indicate it could be ejecta from a past collision involving the Moon. If true, this would mean that 2024 PT5 is not just a visitor to Earth’s orbit but rather a returning fragment of our natural satellite.

Asteroids like 2024 PT5 offer valuable insight into the formation of our solar system, which occurred around 4.6 billion years ago. These remnants of early planetary formation have fascinated scientists for decades. In recent years, NASA has increased its efforts to study and mitigate the potential dangers posed by asteroids. In 2022, the space agency successfully conducted its first Double Asteroid Redirection Test (DART), a mission designed to alter an asteroid’s trajectory. By sending a spacecraft to collide with an asteroid, NASA was able to shorten its orbit by 32 minutes, proving that asteroid deflection is a feasible method for preventing future collisions with Earth.

NASA’s OSIRIS-REx mission also plays a critical role in studying asteroids. The mission, which recently delivered samples from the asteroid Bennu to Earth in September 2023, is providing scientists with valuable data. Although the results from the samples have not yet been made public, researchers are eager to learn more about the composition of Bennu, which poses a potential risk to Earth. According to a 2023 paper published in Icarus, Bennu has a one-in-2,700 chance of colliding with Earth in 2182. This information is crucial as scientists continue to study ways to protect the planet from asteroid impacts.

Although asteroid 2024 PT5 will only be a temporary visitor to Earth’s orbit, its brief journey around the planet highlights the dynamic and unpredictable nature of our solar system. While it may not be visible to most people, the asteroid’s presence offers astronomers a rare opportunity to observe and study a mini-moon up close. As 2024 PT5 makes its way back into deep space, it leaves behind a reminder of the ongoing efforts by scientists to explore and understand the mysteries of the cosmos.