Michigan skywatchers turn eyes to Earth’s new ‘quasi moon’

The moon has company. Astronomers have discovered a new “quasi moon,” a small asteroid called 2025 PN7 that travels alongside Earth. Photo credit: Shutterstock.

Editor’s note: This story was originally published by Bridge Michigan (bridgemi.com), a nonprofit and nonpartisan news organization. To get regular coverage from Bridge Michigan, sign up for a free Bridge Michigan newsletter here (https://bit.ly/BridgeMichiganNewsletter).” 

by Janelle D. James, Bridge Michigan

A faint asteroid discovered in August has joined Earth’s orbiting neighborhood, traveling alongside our planet and behaving like a second moon.

Earth has only one moon, which is about 239,000 miles away. But astronomers recently discovered asteroid 2025 PN7, known as a “quasi moon.”

The Pan-STARRS observatory in Hawaii first detected the object in August. It was later reported to the Minor Planet Center, which tracks and names new celestial bodies, and designated as 2025 PN7.

Asteroid 2025 PN7 is a faint, relatively small space rock — about 60 feet in diameter — that seems to circle Earth, according to EarthSky.

Scientists think it may be a fragment ejected from the moon. The object has likely followed this quasi-moon orbit for roughly 60 years and is expected to remain nearby for about another six decades before moving away.

Over time, asteroid 2025 PN7’s path changes. It shifts between what scientists call a “horseshoe orbit” and its current “quasi-moon” state — and it will eventually switch back again.

A horseshoe orbit is still an orbit around the sun, but from Earth’s viewpoint, it looks like the asteroid is tracing a horseshoe shape in the sky. That means 2025 PN7 will seem to approach Earth from behind, slow down, turn around, and then move ahead of us before repeating the cycle.

Does Earth have two moons? 

Quasi moons behave somewhat like Earth’s moon because they appear to orbit our planet, but they’re actually asteroids that circle the sun along a similar path, according to The Planetary Society.

The newly discovered asteroid is one of seven confirmed quasi moons, according to the Planetary Society.

How to see Asteroid 2025 PN7

The asteroid has an official brightness rating of magnitude 26, which means it can only be seen with powerful telescopes. By comparison, most stars visible to the naked eye are magnitude 6 or brighter, while Sirius, one of the brightest stars, has a magnitude of about -1.5.

Asteroid 2025 PN7 is too small to see to the naked eye but may be spotted using specialized equipment found in observatories.

There are several in Michigan, including:

• University of Michigan’s Detroit Observatory in Ann Arbor
• MSU Observatory in Lansing
• Calvin College Observatory in Grand Rapids
• Sherzer Observatory in Ypsilanti 
• Joseph H. Rodger Observatory in Traverse City 
• Baldwin- Wallace Observatory in Grand Rapids 
• Fox Park Public Observatory in Potterville 
• James C. Veen Observatory in Lowell 

There are also several astronomy clubs across the state.

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by Marsha Chartrand

Marsha Johnson Chartrand, a founder, writer, and copy editor with the Manchester Mirror, is a 50-year resident of Manchester. She has a long history of volunteer and community involvement.