It’s not just the moon that circles Earth each year as we circle the sun. This week, NASA announced another body orbits Earth. A small asteroid named 2016 HO3. While just spotted, 2016 HO3 has been Earth’s little companion for nearly a century. And it’s not going anywhere anytime soon.

Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the JPL, dubs it a quasi-satellite of Earth. It’s too far away to be considered true satellite.

Did You Know: 2016 HO3 isn’t the first quasi-satellite. Chodas describes another asteroid, 2003 YN107, that followed a similar orbital pattern around 10 years ago. YN107 wasn’t as locked into Earth’s orbit as HO3.

2016 HO3 is going to stick with us for a while. “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,” says Chodas.

Scientists don’t know exactly how big the asteroid is, but they have good guess. They believe it’s larger than 120 feet and smaller than 300 feet. And our paths will never cross. Chodas describes the asteroid as being in a “little dance” with our planet.

I’ll let Chodas explain the orbit the asteroid takes around Earth and how our planet’s gravity influences the much smaller body.

“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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Astronomers first learned about 2016 HO3 when it was spotted on April 27, 2016 by the Pan-STARRS 1 asteroid survey telescope in Hawaii.

Pan-STARRS 1 telescope

Located atop Haleakalā on Maui, Hawaii, Pan-STARRS 1 has been scouring the night sky full-time since 2010. It’s armed with one of the largest digital cameras ever built. Each image boasts 1.4 billion pixels each. One of its main goals is to survey as many asteroids in the Solar System as it can, but that’s not its only capability.

Pan-STARRS can peer deep into the Kuiper Belt and discover new KBOs and determine their orbits. And it’s not limited to our solar system.

Pan-STARRS will also catalog 99% of the stars in the northern hemisphere observed by visible light. Obviously, it won’t study every star – but astronomers can use this data to look for stars that vary in brightness. These stars could be eclipsing binaries, supernovae, or even exoplanets.

What we know about asteroids close to Earth grows every day. Check out NASA’s Near-Earth Object website to see how close some of these asteroids are coming to Earth. Thankfully, the bigger ones (that we know about) aren’t coming too close.

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