For most relationships, 100 years is well past the point in time when you can ‘make it official,’ but for planets, it’s just right. After nearly a century in Earth’s orbit, a tiny asteroid has earned NASA’s recognition as Earth’s new “mini moon.” Measuring between 120 feet to 300 feet in diameter, the minuscule rock slowly circles the sun on a similar orbit as Earth and NASA scientists now reveal that it circles Earth as well – not entirely unlike the moon we already know and love.
NASA scientists estimate that Earth’s new playmate, known as “asteroid 2016 HO3,” has probably been around for about 100 years. It was first detected on April 27 by the Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii, which is operated by the University of Hawaii’s Institute for Astronomy. Although the asteroid moon is currently in Earth’s orbit, it may not stay for long—at least in the grand scheme of the timeline of the universe. The asteroid’s own orbit has a unique pattern, doing a slow back-and-forth twist over multiple decades, and it’s expected to continue flirting with our green planet for at least a few more centuries.
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Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory, explains that because of its distance, the new mini moon is a “quasi-satellite” of Earth rather than a true satellite. “The asteroid’s loops around Earth drift a little ahead or behind from year to year, but when they drift too far forward or backward, Earth’s gravity is just strong enough to reverse the drift and hold onto the asteroid so that it never wanders farther away than about 100 times the distance of the moon,” said Chodas. “The same effect also prevents the asteroid from approaching much closer than about 38 times the distance of the moon. In effect, this small asteroid is caught in a little dance with Earth.”
Over the years, other asteroids have done a similar dance with our planet, but those were more like flings than long-term relationships, if we’re going to continue the metaphor. Over 10 years ago, asteroid 2003 YN107 followed a similar orbital pattern for a short time, according to Chodas, but it has since left Earth’s vicinity. “This new asteroid is much more locked onto us,” he said, predicting that it will stick around for “centuries to come.”
Images via NASA/JPL-Caltech