It turns out we are not alone. Earth, that is.
Astronomers have discovered a small asteroid orbiting the sun. As it orbits the sun, however, it remains a constant companion to Earth.
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The asteroid — designated 2016 HO3 — was found on April 27, 2016 by the Pan-STARRS 1 asteroid survey telescope in Hawaii. It is currently estimated to be between 40 and 100 metres in diameter.
“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 Jet Propulsion Laboratory in Pasadena, California.
“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.”
The asteroid spends about half its time closer to the sun than Earth, then loops back around Earth and spends the other half farther away.
“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.”
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This isn’t the first time Earth had a companion.
Asteroid 2003 YN107 followed a similar orbit for some time more than 10 years ago (it has since wandered off). And another asteroid — 2004 GU9 — was also near Earth in 2006.
Scientists believe that there could be hundreds if not thousands of these small asteroids — sometimes referred to as moonlets — that don’t quite get captured by Earth’s gravity but co-orbit with us around the sun.