A small asteroid has been discovered "dancing" with Earth, as the two objects move around the sun together for more than 50 years.
Known as Asteroid 2016 HO3, Earth's "quasi-moon" remained undetected until now, but NASA scientists say it isn't going to get away anytime soon either.
Calculations suggest that 2016 HO3 has been a constant companion of Earth for nearly a century, says Paul Chodas of the Center for Near-Earth Object Studies. This pattern will continue for years to come.
Why Is Asteroid 2016 HO3 Called A Quasi-Satellite?
The asteroid's diameter is estimated to be between 120 feet (37 meters) to 300 feet (91 meters).
Asteroid 2016 HO3 was detected by the Hawaiian asteroid survey telescope called Pan-STARRS 1 on April 27, 2016.
NASA says the asteroid is too far away to hit our planet because it circles around Earth from 14 million kilometers (9 million miles) away.
It's also too distant to be considered as a true satellite of Earth, scientists say, but it is indeed the most stable sample to date of a near-Earth companion or quasi-satellite.
According to Chodas, another asteroid called 2003 YN107 moved along a similar orbital pattern for a brief period more than 10 years ago, but the asteroid has departed Earth's vicinity.
Chodas says asteroid 2016 HO3 is much more secured to Earth than 2003 YN107 had been.
Little Dance With Earth
In its yearly journey around the sun, 2016 HO3 spends almost half of the time closer to the sun than the Earth, passing ahead of our planet.
The asteroid also spends almost half of the time farther away, allowing it to fall behind.
Scientists say the asteroid's orbit is tilted a little, making it bob up and down once each year through the orbital plane of Earth.
As a result, 2016 HO3 is caught in a game of "leap frog" with our planet that will last for centuries.
Over multiple decades, the asteroid's orbit goes through a gentle back-and-forth twist.
Chodas says 2016 HO3's circling movement around Earth drift a little behind or ahead every year, but when the orbits drift too backward or too forward, the gravity of Earth is strong enough to reverse the drift and hold on the asteroid.
Because of that, the asteroid never wanders too far away than about 100 times the distance of the moon, says Chodas. This effect also prevents 2016 HO3 from approaching much closer than 38 times the distance of the moon.
"In effect, this small asteroid is caught in a little dance with Earth," adds Chodas.
A Rare Cosmic Event
The cosmic path of asteroid 2016 HO3 alone is enough to turn it into an object of interest for scientists, Chodas says, although they have yet to gather details about the asteroid's composition and origin.
Chodas told The Christian Science Monitor that the event is rare because the asteroid is in an orbit that is essentially the same as that of Earth.
While NASA has to consider it first, Chodas says the uncommon positioning of the asteroid makes it an attainable target for future studies as interest in asteroids increases.
"It's a potential mission target," adds Chodas.
The possibility, however, is slim as of now.
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