First spotted by researchers over the summer, the newly discovered rock isn\u2019t a true moon but rather an asteroid that travels around the sun in near-lockstep with Earth \u2014 making it appear, from our perspective, as if it\u2019s orbiting our planet.<\/p>\n
But unlike the actual moon, 2025 PN7 is just shadowing us in a synchronized path, says Northeastern University assistant professor Jacqueline McCleary<\/a>, an observational cosmologist.<\/p>\n The celestial object belongs to the Arjuna asteroid group, a collection of \u201cnear-Earth objects\u201d that move in resonance with Earth. Because 2025 PN7 is not gravitationally bound to our planet like the moon is, it\u2019s not a \u201ctrue\u201d moon.<\/p>\n But according to McCleary, there\u2019s no simple rule for what counts as a moon and what doesn\u2019t. She says that astronomers have long quibbled about criteria \u2014 debating everything from size cutoffs to orbital stability.<\/p>\n Most astronomers prefer the term \u201cnatural satellite\u201d to \u201cmoon\u201d or \u201cmoonlet,\u201d which have no universally accepted definitions, McCleary says.\u00a0<\/p>\n \u201cWithin this, there is an enormous amount of variation, even within our own solar system: from Mars\u2019s moons Phobos and Deimos, which are little more than captured asteroids, to the Galilean satellites of Jupiter, which are almost the size of Earth and have features like subsurface oceans and volcanoes,\u201d McCleary says.\u00a0<\/p>\n The quasi-moon has likely been our close neighbor for some 60 years, experts say. But the asteroid is so small that it can hardly be seen without a large telescope that is also capable of scanning large areas of the sky, says Northeastern University astrophysicist Jonathan Blazek<\/a>.\u00a0\u00a0<\/p>\n Researchers from the University of Hawaii, working at a research facility in Haleakala, Hawaii, discovered the quasi-moon in July using the Pan-STARRS telescope, which Blazek says is optimized for finding new objects in our solar system, as well as other astronomical \u201ctransients\u201d \u2014 cosmological phenomena that change, such as supernovae.<\/p>\n \u201cThe Rubin Observatory, which just started taking data earlier this year, and with which I am involved, is an even larger telescope that will find many new solar system objects,\u201d he says.\u00a0<\/p>\n Blazek and McCleary note that there are other such partial, temporary or quasi moons hanging around the planet. In fact, at least six of them.\u00a0<\/p>\n \u201cThese objects are all on similar orbits to the Earth and remain reasonably stable over many years,\u201d Blazek says.<\/p>\n In 2024, Earth had a brief companion in 2024 PT5<\/a>, an asteroid that loosely orbited the planet for a few months, McCleary says.\u00a0\u00a0<\/p>\n But 2025 PN7 is expected to hang around Earth until 2083, at which point it will drift off into space.<\/p>\n \u201cIn the long term, the orbits will drift, and the quasi-moons will move away,\u201d Blazek says. \u201c2025 PN7 is expected to stick around for roughly another 60 years.\u201d<\/p>\n Experts say 2025 PN7 will have virtually no gravitational impact on Earth due to it being quite small, astronomically speaking.\u00a0<\/p>\n Blazek estimates that the quasi-moon is \u201croughly the size of a small office building,\u201d compared to the moon, which he calculates is \u201cabout a quadrillion (10^15) times more massive.\u201d<\/p>\n \u201cAt only 20 meters across, it\u2019s far too small to have a measurable effect on the Earth\u2019s tides or anything else,\u201d McCleary says.<\/p>\n Tanner Stening is an assistant news editor at Northeastern Global News. Email him at t.stening@northeastern.edu. Follow him on X\/Twitter @tstening90<\/a>.<\/p>\n![\"Jacqueline](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/10\/Jacqueline-McCleary_1400.jpg\")
09\/27\/22 \u2013 BOSTON, MA. \u2013 Jacqueline McCleary, associate professor in the College of Science, poses for a portrait on Tuesday Sept. 27, 2022. Photo by Matthew Modoono\/Northeastern University<\/p>\n![\"Jonathan](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/10\/Jonathan_Blazek_1400.jpg\")
10\/13\/23 \u2013 BOSTON, MA. \u2013 Jonathan Blazek, assistant professor of physics, poses for a portrait on Oct. 13, 2023. Photo by Matthew Modoono\/Northeastern University
\nJacqueline McCleary, an observational cosmologist, and Jonathan Blazek, an assistant professor physics, say that the quasi-moon has likely been our close neighbor for some 60 years. Photos by Matthew Modoono\/Northeastern University<\/p>\n