Earth’s Temporary Mini-Moon: 2024 PT5
In an astronomical event set to occur this month, Earth will temporarily capture a small asteroid named 2024 PT5, often referred to as a “mini-moon.” This asteroid will orbit our planet from September 29 to November 25. Following that, it broke free and resumed its cosmic mission.
What is 2024 PT5?
2024 PT5 is a small asteroid that will not collide with Earth but will briefly orbit it, much like the Moon. The duration of this orbit is roughly two months. Astronomers refer to the comparatively common occurrence of an asteroid momentarily orbiting Earth as a “temporarily captured flyby.” This indicates that even though the asteroid will be pulled into Earth’s orbit, it won’t finish its orbit.
According to a paper published in the Research Notes of the American Astronomical Society, 2024 PT5 was detected by the Asteroid Terrestrial-Impact Last Alert System (ATLAS) on August 7, 2024. The asteroid will break free from Earth’s gravitational pull around November 25, 2024.
Origin and Future Encounters
A study published by Live Science suggests that 2024 PT5 likely originated from the Arjuna asteroid belt, a region of space rocks that orbit the sun near Earth. Due to its orbit’s similarity to Earth’s, calculations indicate that 2024 PT5 will return to orbit Earth in January 2025 and again in 2055.
Is It Normal for Earth to Capture Asteroids?
Earth periodically captures asteroids from the Near-Earth Object (NEO) population, temporarily turning them into mini-moons. NASA categorized larger objects within 4.7 million miles (7.5 million kilometers) of Earth as “potentially hazardous,” and designates any item near 120 million miles (190 million kilometers) of Earth as a NEO.
NASA uses ATLAS, a network of four observatories that surveys the whole night sky once a day, to monitor about 28,000 asteroids. 2024 PT5 is classified as an Apollo-class NEO and is part of this population, following a path similar to a previous mini-moon, 2022 NX1.
Previous Instances of Mini-Moons
Earth has captured mini-moons before. Here are a few notable examples:
- 2020: A mini-moon turned out to be space junk, specifically a rocket booster from the 1966 Surveyor 2 Centaur launch.
- 2022 NX1: This asteroid became a mini-moon in 1981 and 2022, and is expected to return in 2051.
- 2006 RH120: This asteroid orbited Earth for an entire year, from July 2006 to July 2007.
Some researchers believe Earth may always have at least one mini-moon orbiting nearby, due to the consistency of these events.
Can We See 2024 PT5?
Although 2024 PT5 will pass close to Earth for 57 days, it will be too small and dim to be seen with the naked eye. The asteroid is just 33 feet (10 meters) across, and even with a telescope, it is too faint to be seen due to its precise magnitude of 27.593. For comparison, the dimmest objects visible to the naked eye have a magnitude of around 6.5, while a 12-inch telescope can only detect objects with a magnitude of 16 or 17.
Scientific Observations
Despite its invisibility to amateur astronomers, professional astronomers will be able to observe 2024 PT5 using powerful telescopes. Carlos de la Fuente Marcos, a professor at the Universidad Complutense de Madrid, explained that a telescope with a diameter of at least 30 inches, along with advanced detectors as CMOS or CCD, in order to view this mini-moon.
Marcos and his team intend to carry out detailed spectroscopic and photometric observations of 2024 PT5 to gain more insight into its nature. These studies may reveal new information about the asteroid’s composition and behavior.
Mini-Moon Events and Their Types
Mini-moon events occur when small celestial bodies, such as asteroids, temporarily become gravitationally bound to Earth. There are two types of mini-moon events:
- Long-term events: In these instances, the asteroid completes one or more full orbits around Earth. These gravitational interactions may continue for many years.
- Short-term events: These engagements last for only days, weeks, or a few months, and the asteroid does not complete a full orbit.
2024 PT5 belongs to the second category, as it will be temporarily captured by Earth’s gravity for about two months without completing a full orbit. According to Marcos, this asteroid is akin to a “window shopper,” briefly visiting Earth before returning to its path around the sun.
The Role of the Arjuna Asteroid Belt
2024 PT5 is part of the Arjuna asteroid belt, a collection of space rocks that follow orbits similar to Earth’s at an average distance of about 93 million miles (150 million kilometers) from the sun. These objects sometimes approach Earth at close ranges, around 2.8 million miles (4.5 million kilometers), and at slow velocities of around 2,200 miles per hour (3,540 kilometers per hour). Under these conditions, an asteroid’s geocentric energy can become negative, allowing it to temporarily become a mini-moon.
The Ejection of Mini-Moons
Mini-moons are eventually ejected from their orbits around Earth due to gravitational disturbances caused by the sun. After its brief stay as Earth’s second moon, 2024 PT5 will return to its sun-centered orbit, remaining part of the Arjuna asteroid belt.
A Common Phenomenon
Short-term mini-moon events like 2024 PT5 occur relatively frequently, with several events happening each decade. However, long-term capture episodes, in which asteroids remain in orbit around Earth for a year or more, are much rarer. Earth experiences these only once every ten to twenty years.
Conclusion
While 2024 PT5’s stay as a mini-moon will be brief and invisible to most, it represents another fascinating example of Earth’s dynamic interaction with near-Earth objects. As scientists continue to monitor and study these events, they provide valuable opportunities to learn more about the nature of asteroids and their potential impact on our planet.
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