It has been orbiting the Earth for at least 100 years but wasn’t discovered until a few months ago. Could that be because this tiny space object may only be 40 meters in diameter? Will it stay in its remote orbit or get close enough to cause a catastrophic collision? What should we call it – a little luna? Mini-mini-moon?
Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the Sun, we refer to it as a quasi-satellite of Earth.
In the announcement by NASA of the discovery, Paul Chodas of the Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory reveals that asteroid 2016 HO3 was first spotted on April 27, 2016, by the Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii.
Its estimated diameter is between 37 and 91 meters (120-300 feet) and its remote orbit keeps the space between it and Earth at about 38 to 100 times the distance of the Moon. Chodas describes the orbit as a “little dance with Earth” that keeps 2016 HO3 from moving far enough away to escape Earth’s gravity but not close enough to become a threat – its closest distance is still 9 million miles (14 million km) away.
One other asteroid — 2003 YN107 — followed a similar orbital pattern for a while over 10 years ago, but it has since departed our vicinity. This new asteroid is much more locked onto us. 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.
Is 2016 HO3 a lonely little only-child quasi-satellite? Probably not. Where there’s smoke, there’s fire, and where there’s asteroids, there’s … more asteroids. In 2012, researchers at the University of Helsinki calculated "that at any given time there should be at least one asteroid with a diameter of at least one meter orbiting Earth."
Are we in any danger from 2016 HO3? On the one hand, NASA says 2016 HO3 will stay in its wobbly orbit for hundreds of years and there’s nothing to worry about. On the other hand … it’s bigger than the asteroid that caused the 1908 Tunguska event.
Still think it’s nothing to worry about?