For the next two months, Earth will have a cosmic guest. A so-called “mini moon” will join our actual moon in circling the planet until Nov. 25.
What exactly is the mini moon? It’s actually a small asteroid –– only 33 meters across, the size of a bus and 300,000 times smaller than Earth’s — that has temporarily entered Earth’s gravitational pull, says Jacqueline McCleary, an assistant professor of physics at Northeastern University.
“Perturbations — little kicks from Jupiter’s gravity, the sun’s gravity, Earth’s gravity — can sometimes knock an object a little bit closer so that it falls in towards the Earth,” McCleary explains. “For an object to be orbiting or be a satellite, it would have to be traveling at a speed lower than the escape velocity.”
“So, technically, it will be captured by the Earth’s gravitational potential,” she adds. “But instead of doing a complete orbit like a regular moon, it’s more going to be deflected and then come back in and then kicked back out again and return to more or less its previous orbit around the sun.”
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Photo by NASA
