NASA has confirmed that a small asteroid, named 2025 PN7, has been captured in a quasi-orbital relationship with Earth, effectively acting as a “second moon”. The asteroid, first observed by the University of Hawaii’s Pan-STARRS telescope at Haleakalā Observatory in August 2025, is expected to accompany Earth until 2083.
Discovery and Observation
- Discovered by: University of Hawaii team
- Telescope used: Pan-STARRS (Panoramic Survey Telescope and Rapid Response System)
- Location: Haleakalā Observatory, Hawaii
- Date of discovery: August 2025
- Estimated size: 18–36 meters (about the height of a small building)
- Distance from Earth: Up to 4 million km (≈10 times farther than the Moon)
- Orbital relationship: Similar to Earth’s orbit around the Sun (heliocentric orbit)
Despite being in Earth’s cosmic neighborhood for nearly 60 years, its existence was only confirmed through detailed tracking and analysis of orbital patterns in 2025.
What is a Quasi-Moon?
A quasi-moon is a type of near-Earth asteroid (NEA) that orbits the Sun, not the Earth directly, but stays in a synchronized path with Earth for an extended period.
These objects appear to trail or lead Earth, giving the illusion of a secondary moon when observed from our planet.
Key Features of Quasi-Moons
- They are gravitationally bound to the Sun, not Earth.
- Their orbits closely resemble Earth’s orbit, creating a temporary partnership.
- They may stay in this synchronized orbit for decades or centuries before drifting away.
- 2025 PN7 is projected to remain in Earth’s vicinity until 2083, after which it will transition into a horseshoe orbit– appearing to loop around Earth in the sky.
Orbital Characteristics of 2025 PN7
- Orbit type: Sun-centered, Earth-like orbit
- Orbit behavior: Alternates between being slightly inside and slightly outside Earth’s orbit
- Apparent motion: Sometimes appears to orbit Earth due to relative motion differences
- Distance variations:
- Closest approach: ~186,000 miles (~300,000 km)
- Average distance: ~4 million km (10× the Moon’s distance)
- Brightness: Extremely faint (Magnitude 26) — not visible to the naked eye
When closer to the Sun, PN7 moves faster than Earth; when farther, it slows down, producing the visual illusion of orbiting our planet.
Difference Between Quasi-Moons and Mini-Moons
| Feature | Quasi-Moon | Mini-Moon |
| Orbit | Around the Sun (Earth-like orbit) | Temporarily around Earth |
| Duration | Decades to centuries | Few months |
| Example | 2025 PN7, Kamoʻoalewa | 2020 CD3 (captured briefly in 2024) |
| Visibility | Very dim and small | Usually detected briefly before escaping orbit |
Thus, 2025 PN7 is not a permanent moon, but a long-term companion asteroid sharing Earth’s orbital path.
Scientific Significance
- Offers insights into orbital dynamics and gravitational interactions between Earth and near-Earth objects (NEOs).
- Helps refine models of asteroid motion, capture, and stability in Earth’s gravitational influence.
- Serves as a potential test case for studying low-gravity exploration, asteroid mining, and planetary defense strategies.
- Its discovery highlights the effectiveness of modern survey telescopes like Pan-STARRS in tracking small, faint celestial objects.
Visibility to the Public
- Not visible to the naked eye.
- Due to its small size and dim magnitude (26), 2025 PN7 requires large, high-powered telescopes for observation.
- Skywatchers cannot see it — professional astronomers use repeated long-exposure images to track its movement.
Context and Related Discoveries
- Number of known quasi-moons: Around six previously identified near-Earth quasi-moons.
- Recent similar events: In 2024, Earth temporarily captured a mini-moon (asteroid 2020 CD3) that orbited Earth for about two months before escaping.
- The discovery of 2025 PN7 reinforces that Earth’s gravitational sphere frequently interacts with small asteroids.
Projects Involved
- Pan-STARRS (Hawaii): Key in discovering and tracking near-Earth objects (NEOs).
- LSST Survey (Rubin Observatory, Chile): Expected to enhance detection of small and faint celestial bodies.
- These global initiatives mark a new era in asteroid detection, planetary monitoring, and space situational awareness.
Significance for Astronomy
- Expands understanding of Earth’s near-space environment.
- Illustrates that our Solar System hosts many transient companions beyond the known planets and moons.
- Demonstrates advancements in automated sky survey technology and data-driven astronomy.
- Encourages further international collaboration in tracking potentially hazardous asteroids (PHAs) and co-orbital bodies.