‘Dancing’ with Earth: NASA discovers tiny asteroid companion

© NASA Jet Propulsion Laboratory
Move over, Moon – Earth has as new celestial companion. A tiny asteroid, named 2016 HO3, has been engaged in a steady orbital “dance” with our planet for almost a century, but was discovered only recently.

A telescope on Haleakala, Hawaii – funded by NASA’s planetary defense program – spotted the asteroid in April and designated it 2016 HO3. The actual size of the celestial body has not been firmly established, but astronomers have estimated that its diameter is larger than 120 feet (40 meters) and smaller than 300 feet (100 meters).

NASA’s Jet Propulsion Laboratory in Pasadena, California released a video of the asteroid’s orbit on Wednesday, which is based on calculations that show 2016 HO3 has been Earth’s “stable quasi-satellite” for almost a century and will remain our planet’s companion for centuries to come.

“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,” said Paul Chodas, manager of NASA's Center for Near-Earth Object (NEO) Studies at the JPL.

The small space rock seems to suffer from approach anxiety, never getting closer than nine million miles (14 million kilometers) from Earth. By comparison, the Moon is just a cozy 238,900 miles (385,000 km) away.

Still, 2016 HO3 is Earth’s most loyal and stable semi-satellite.

“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 explained. “This new asteroid is much more locked onto us.”

For about half of its orbit, the asteroid is closer to the Sun than it is to our planet, scientists at the JPL say. However, Earth’s gravity is just strong enough to reverse the drift and hold on to the asteroid, meaning it never strays farther than about 100 times the distance of the Moon.

“The same effect also prevents the asteroid from approaching much closer than about 38 times the distance of the moon,” said Chodas. “In effect, this small asteroid is caught in a little dance with Earth.”