A space rock is about to become Earth’s new ‘mini-moon’ | CNN

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Earth is on the brink of acquiring a new "mini-moon," although it won't last here for an extended period.

Astronomers have announced that a recently identified asteroid, called 2024 PT5, will be briefly pulled in by Earth's gravitational pull and will circle our planet from September 29 until November 25. After this period, the asteroid will move back into its path around the sun.

This month, information on the brief mini-moon and its horseshoe-shaped orbit was shared in the Research Notes of the American Astronomical Society.

Astronomers initially detected the asteroid on August 7 at an observatory in South Africa that is part of the NASA-funded Asteroid Terrestrial-impact Last Alert System, known as ATLAS.

According to Carlos de la Fuente Marcos, the main author of the study and a researcher at the Complutense University of Madrid in the field of mathematical sciences, the asteroid is estimated to be approximately 37 feet (11 meters) wide. However, additional observations and information are necessary to verify its true size.

The asteroid in question could measure anywhere from 16 to 138 feet (5 to 42 meters) in diameter, potentially making it larger than the one that entered Earth's atmosphere over Chelyabinsk, Russia, in 2013. That particular asteroid had a diameter of about 55 to 65 feet (17 to 20 meters) and detonated in the sky, releasing energy equivalent to 20 to 30 times that of the atomic bomb dropped on Hiroshima, Japan. The explosion produced a brightness that exceeded that of the sun. Debris from this event caused damage to over 7,000 buildings and injured more than 1,000 individuals.

According to de la Fuente Marcos, Asteroid 2024 PT5 is not a threat to Earth, either now or in the coming decades, despite being called a mini-moon. This asteroid will travel in its orbit approximately 2.6 million miles (4.2 million kilometers) from our planet, which is around ten times further than the distance from Earth to the moon.

According to de la Fuente Marcos, mini-moon events can be categorized into two types.

Extended events involve asteroids known as temporarily captured orbiters, which can orbit our planet for one or more years before moving on. In contrast, during brief events, the asteroid doesn't make a complete trip around the Earth.

These brief visitors, often referred to as temporary flybys, are similar to 2024 PT5 in that they function as mini-moons for just a few days, weeks, or a couple of months, he explained.

Earth has had other short-term mini-moons in the past, including one called Asteroid 2020 CD3. This asteroid was initially seen orbiting our planet in February 2020, but it left a few months later. Studies indicate that it had actually been circling Earth for several years before it was finally observed.

Asteroid 2020 CD3 is thought to be a mini-moon that has been captured by Earth's gravity for an extended period. In contrast, the recently discovered Asteroid 2024 PT5 is classified as having a brief period of capture.

Brief mini-moon occurrences can happen multiple times within a decade, but extended mini-moon events are uncommon and take place only every 10 to 20 years, according to de la Fuente Marcos.

It’s challenging for asteroids to become mini-moons since they need to be moving at the exact speed and angle for Earth's gravity to pull them in.

“To transform into a mini-moon, an object heading toward Earth needs to move in slowly and get close,” explained de la Fuente Marcos.

Asteroids that turn into mini-moons approach Earth at distances of up to 2.8 million miles (4.5 million kilometers) and travel at speeds below 2,237 miles per hour (3,600 kilometers per hour), he noted.

Robert Jedicke, an expert at the University of Hawaii’s Institute for Astronomy, explained in an email that an asteroid's likelihood of being captured by Earth isn't influenced by its size or weight. Instead, it depends solely on how fast and in what direction it is moving when it nears the Earth-Moon system. He noted that most asteroids that come close to Earth do so at speeds and angles that make capture impossible. However, there are rare instances when the gravitational forces from various celestial bodies in the solar system align in such a way that a slower-moving asteroid approaching at the right angle can be temporarily captured by Earth.

Jedicke did not participate in the recent research.

Asteroid 2024 PT5 originated from the Arjuna asteroid belt, a collection of smaller asteroids that circle the sun in paths similar to that of Earth.

According to Jedicke, it's believed that there’s roughly one small moon, comparable in size to a dishwasher, orbiting within the Earth-Moon system at any given moment. However, these small moons are challenging to spot, which means that most of them remain unnoticed while they are gravitationally tied to Earth. He noted that 2024 PT5 is estimated to be around 10 meters wide, potentially making it the largest identified captured object so far.

According to Jedicke, mini-moons might be asteroids originating from the primary asteroid belt that lies between Mars and Jupiter. They could also be pieces of the Moon's surface that were ejected due to asteroid collisions that occurred millions of years ago.

"Figuring out their origin might give us insights into how craters are formed and the way material is launched from the Moon’s surface," he stated.

De la Fuente Marcos and his team aim to study 2024 PT5 to gather additional information with the Gran Telescopio Canarias and the Two-Meter Twin Telescope, which are located in the Canary Islands of Spain. However, as he pointed out, the asteroid will be too faint and small for anyone using amateur telescopes or binoculars to see. Additionally, it won't have any noticeable impact on our planet.

In approximately 56.6 days, the Sun's gravity will pull Asteroid 2024 PT5 back into its usual orbit.

However, the asteroid is projected to pass by Earth at a distance of about 1.1 million miles (1.7 million kilometers) on January 9, 2025. After this close approach, it will move away from our planet and won't be back until 2055, as outlined in the research.

When Asteroid 2024 PT5 returns, scientists predict it will temporarily become a mini-moon for Earth, for a brief period in November 2055 and then again for several weeks in early 2084.