Newfound Asteroid is 'Quasi-Moon' of Earth, JPL Scientist Announces

Published : Friday, June 17, 2016 | 4:25 AM

The newfound asteroid 2016 HO3 has an orbit around the sun that keeps it as a constant companion of Earth. Credit: NASA/JPL-Caltech

Scientists working out of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena have discovered a small asteroid that has been in an orbit around the sun and is a constant companion of Earth.

It now appears the asteroid, designated as 2016 HO3, will remain a “quasi-moon” of Earth for centuries to come, being too distant to be considered a true satellite of the planet.

Paul Chodas, manager of the Center for NEO Studies, said 2016 HO3 loops around Earth, but never ventures too far away as it, too, goes around the sun.

“This new asteroid is much more locked onto us,” Chodas says. “Our calculations indicate 2016 HO3 has been a stable quasi-satellite of Earth for almost a century, and it will continue to follow this pattern as Earth’s companion for centuries to come.”

One other asteroid – 2003 YN107 – followed a similar orbital pattern for a while over 10 years ago, but it has since departed our vicinity, Chodas said.

In its yearly trek around the sun, asteroid 2016 HO3 spends about half of the time closer to the sun than Earth and passes ahead of Earth, and about half of the time farther away, causing it to fall behind, JPL scientists said.

Its orbit is also tilted a little, causing it to bob up and then down once each year through Earth’s orbital plane. In effect, this small asteroid is caught in a game of leap frog with Earth that will last for hundreds of years.

Chodas says the asteroid’s orbit also undergoes a slow, back-and-forth twist over multiple decades.

“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.”

Asteroid 2016 HO3 was first spotted on April 27, 2016, by the Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii, operated by the University of Hawaii’s Institute for Astronomy and funded by NASA’s Planetary Defense Coordination Office.

The size of this object has not yet been firmly established, but it is likely larger than 120 feet or 40 meters, and smaller than 300 feet or a hundred meters.

The JPL’s Center for NEO Studies website has a complete list of recent and upcoming close approaches, as well as all other data on the orbits of known NEOs. , so scientists and members of the media and public can track information on known objects.

As for 2016 HO3, NASA said the asteroid does not pose a threat to the planet.

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