Earth's Second Moon - but not for long.

imhotep

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  • Mar 29, 2017
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    NASA scientists have calculated that Earth will capture a "second moon" on Sunday (Sept. 29). The "mini-moon" comes in the form of the tiny asteroid 2024 PT5, which usually orbits the sun as part of a small asteroid belt that follows Earth.

    While Earth's primary companion, the moon, has lingered around our planet for around 4 billion years since its formation in the solar system's infancy, this asteroid will be a temporary fixture that won't even see the year out.

    "According to the latest data available from NASA's Jet Propulsion Laboratory Horizons system, the temporary capture will start at 15:54 EDT (1954 UTC) and will end at 11:43 EDT (1543 UTC) on November 25," mini-moon event expert and Universidad Complutense de Madrid professor Carlos de la Fuente Marcos told Space.com on Wednesday (Sept. 25).

    "The object that is going to pay us a visit belongs to the Arjuna asteroid belt, a secondary asteroid belt made of space rocks that follow orbits very similar to that of Earth at an average distance to the sun of about 93 million miles (150 million kilometers)," Marcos told Space.com last week. "Objects in the Arjuna asteroid belt are part of the near-Earth object population of asteroids and comets."

    Though the idea of Earth getting a second moon sounds extraordinary, these gravitational capture events are actually quite common.

    "Some Arjuna asteroid belt objects can approach Earth at a close range of around 2.8 million miles (4.5 million kilometers) and at a relatively low velocity of less than 2,200 miles per hour (3,540 km/h)," Marcos explained. "Asteroid 2024 PT5 will not describe a full orbit around Earth. You may say that if a true satellite is like a customer buying goods inside a store, objects like 2024 PT5 are window shoppers."