Why should Saturn and Jupiter have all the new moon fun? Turns out planet Earth has a newly-discovered natural satellite, too.
That’s technically correct, because to call the object a proper “moon” is too strong. Actually, 2023 FW13 is a “quasi-moon.” Specifics of the space rock’s orbital characteristics make the difference.
Researchers discovered 2023 FW13 using the Pan-STARRS telescope atop Hawaii’s Haleakala volcano, the Daily Mail reported. The team thinks it will likely stay with us until 3700 CE, at which point it could spin out of its enormous orbit.
And I mean enormous: 2023 FW13 joins a handful of known quasi-moons, which are satellites that orbit around the sun gravitationally, but also happen to loop the Earth into their broad circuits.
“The dimension of the loop (about 0.18 astronomical units in radius) is so large that Earth plays essentially no role in its motion,” Alan Harris, senior research scientist at Boulder, Colorado’s Space Science Institute, told Sky & Telescope.
To wit, our new astronomical neighbor doesn’t reside all that close to us. Earth’s “Hill sphere,” or the distance within which it can capture objects in orbit, surrounds us out to a distance of about 1.5 million kilometers.
The moon (the familiar one) orbits at 0.38 million kilometers. In contrast, 2023 FW13 doesn’t come closer to us than about 2.57 million kilometers. It’s also incredibly small, one expert estimated it to be about 15 meters across.
Its far-ranging, elliptical orbit brings it “halfway to Mars and halfway to Venus,” according to the Daily Mail. And yet, it takes almost exactly the same time as we do to make a trip around the sun, completing a circuit in 365.42 days.
Pan-STARRS first registered the little object on May 28. Other telescopes confirmed its existence and the Minor Planet Center at the International Astronomical Union (IAU) formally listed it shortly after.
The Pan-STARRS telescope at sunset. Photo: Wiki Commons
