NASA has just declared that Earth appears to have a second moon that has been orbiting around our planet for nearly a century.
This second moon doesn’t quite resemble the one we’re used to seeing in the starry night sky, however. Actually an asteroid, it has been discovered in an orbit around the sun that keeps it as a constant companion of Earth, and will continue to do so for centuries.
This new asteroid, called 2016 HO3, is too distant to be considered a true satellite of our planet, but is the best and most stable example of a near-Earth companion we’ve yet to come across.
“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,” explained Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California. “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”
This second “moon,” discovered by the Pan-STARRS 1 asteroid survey telescope located in Haleakala, Hawaii, is tilted at eight degrees, which is considered to be highly elliptical. This makes it able to travel within the ranges of 38 to 100 times the distance of our “first moon.”
The asteroid makes its way around the sun for 365.93 days, slightly longer than Earth’s 365.24. It spans about 40 meters across and is about 100 meters wide. Expected to never get closer than about 14 million kilometers from Earth, scientists believe 2016 HO3 will never stray off its course more than 40 million kilometers.