As Americans joke, the «second moon» of the Earth did not stay for Thanksgiving, but visited the «family» the day before. Scientists have confirmed the correctness of the unofficial name of the asteroid 2024 PT5.
The study of the asteroid, which will leave the Earth’s environment on Monday, November 25, shows that it is made of material ejected from the real Moon after one of the ancient collisions that left the Earth’s satellite covered with craters. The leading theory of the Moon’s formation, called the «giant collision hypothesis», suggests that the Moon appeared about 4 billion years ago as a result of molten material being ejected from the Earth, which subsequently cooled and condensed. This means that the Earth is probably also the «mother of the» and the «second» Moon.
«There is some evidence that this asteroid may be of lunar origin. Current studies indicate its rapid rotation with a period of less than one hour, which can be expected if 2024 PT5 is a large boulder from the lunar surface or a fragment of a larger object,» says Carlos de la Fuente Marcos, lead author of the discovery and professor at Complutense University of Madrid.
The lunar origin of the asteroid is also evidenced by its spectrum. According to it, the chemical composition of 2024 PT5 matches well with lunar material previously delivered to Earth by space missions.
The celestial object comes from the Arjuna secondary asteroid belt, which consists of rocks that move in an orbit around the Sun, very similar to the Earth’s orbit, and are located at an average distance of about 150 million km from our star.
«Some objects of the Arjuna asteroid belt can approach the Earth at a close distance, about 4.5 million km, and at a relatively low speed, less than 3540 km/h. Asteroid 2024 PT5 does not describe a complete orbit around the Earth. You can say that if a real satellite is like a customer shopping in a store, then objects like 2024 PT5 are just looking at the windows,» explains Prof. Marcos.
Traveling «small moon» fall into two categories. These are events with a long stay near the Earth, during which the asteroid makes one or more complete revolutions around our planet over one or more years, and short approaches, during which the body does not make a single complete rotation. The latter last for days, weeks, or even several months.
The conditions for the orbit (distance of 4.5 million km and 3540 km/h) were met by the asteroid on September 29, 2024. The «stay of» 2024 PT5 will end today, November 25), when the Sun’s gravity will break its orbit. The asteroid will return to its «second family» — Arjuna belt.
Thanks to the astrometry obtained from the Teide Observatory, the determination of the orbit of 2024 PT5 has been significantly improved. This made it possible to learn that the study of the asteroid can be continued when it approaches Earth again on January 9, 2025.
The study also shows that there is evidence that other bodies in the Arjuna asteroid belt also owe their origin to the Moon.
«In the 2024 lunar ejecta scenario, PT5 could be a large boulder from the lunar surface that was ejected into space after a cratering event, subsequently dynamically evolving to an orbit within the Arjun asteroid belt. This object has helped us realize that lunar ejecta are likely the main source of the material that forms the Arjuna asteroid belt,— says Marcos.
The study has been accepted for publication in the journal Astronomy & Astrophysics and is available in the preprint repository arXiv.
Source: Space.com
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