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Asteroids

Earth's Quasi-Moons: A Newfound Companion

Strategic Insights

— 1 min read

Astronomers at the Pan-STARRS observatory in Hawaii discovered a new quasi-moon, named 2025 PN7, which has been in a quasi-orbit around Earth for about 60 years. This development adds to the existing list of seven quasi-satellites, with the majority having Earth-like orbits. The study, published in Research Notes of the AAS, highlights the dynamic context of the Arjuna asteroid belt, where these quasi-moons inhabit. Researchers have been tracking these near-Earth objects to understand their behavior and implications for planetary defense and future space missions.

Key Takeaways:

  • The newly discovered quasi-moon, 2025 PN7, has been in a quasi-orbit for about 60 years and is expected to remain nearby for another 60 years.
  • The quasi-moon has a relatively short total time of 128 years, compared to the 381-year expected near-Earth orbit of Kamo'oalewa.
  • The study authors explain that quasi-satellites, including 2025 PN7, are distinct from mini-moons, which temporarily orbit Earth.
  • Currently, there are six other known quasi-moons: 164207 Cardea (2004 GU9), 469219 Kamo'oalewa (2016 HO3), 277810 (2006 FV35), 2013 LX28, 2014 OL339, and 2023 FW13.
  • Researchers have been tracking these near-Earth objects since 1991, when the first quasi-moon was discovered.
  • The study highlights the importance of keeping track of these objects for planetary defense and future space missions.

Statistics:

  • The median value of r in the year interval (2000, 2050) is displayed as r.
  • The equivalent value for the semimajor axis is a'.
  • 2025 PN7 has been in a quasi-orbit for 60 years.
  • The total time for 2025 PN7 is 128 years.
  • Kamo'oalewa has an expected near-Earth orbit of around 381 years.

Sources:

  • Research Notes of the AAS, "Meet Arjuna 2025 PN7, the Newest Quasi-satellite of Earth" (2025). DOI: 10.3847/2515-5172/ae028f
  • Phys.org, "Scientists find quasi-moon orbiting the Earth for the last 60 years--and it's not the first one" (2025, September 10) retrieved 10 September 2025 from https://phys.org/news/2025-09-scientists-quasi-moon-orbiting-earth.html

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