2025 GN1
Second closest-orbiting asteroid to the Sun, paired with 2021 PH27.
2025 GN1 is a near-Earth asteroid that orbits entirely within Earth’s path, classifying it as an Atira type. It was discovered on 4 April 2025 using the Dark Energy Camera (DECam) on the Víctor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile. The discovery observations were made by astronomers H. Perkins, T. Murphey, Jan Kleyna, and Robert Weryk. Follow-up observations over the next week were provided by T. Linder and R. Holmes using a 1.3-meter telescope at the same observatory. The Minor Planet Center (MPC) announced the discovery on 13 April 2025, based on five nights of data.
Shortly after its discovery, teams led by Scott S. Sheppard and Albino Carbognani independently noticed that 2025 GN1’s orbit closely matched that of 2021 PH27, the closest-orbiting asteroid to the Sun known at the time. This suggested the two might share a physical origin, with identical colors and compositions. Follow-up observations on 14–16 April 2025 using the Magellan–Baade and Gemini South telescopes confirmed these predictions.
The asteroid’s provisional designation, 2025 GN1, was assigned by the MPC as a shorthand for its discovery date. Before that announcement, it carried the internal temporary label JKt019. Once its orbit is well determined over multiple years, the MPC will assign a permanent minor planet number, making it eligible for a formal name.
2025 GN1 orbits the Sun at an average distance (semi-major axis) of 0.462 AU (about 69.1 million km), completing one orbit every 114.7 days. As of 2026, it is the second closest-orbiting asteroid to the Sun and the second shortest-period asteroid, just behind its kin 2021 PH27. Its orbit is highly tilted (inclination of 32.8° to the ecliptic) and very elongated (eccentricity 0.71). At perihelion it comes as close as 0.136 AU (20.3 million km) to the Sun, and at aphelion it reaches 0.788 AU (117.9 million km). Because its entire orbit lies inside Earth’s, it is an Atira-type near-Earth asteroid, though it never comes closer than 0.22 AU (33 million km) to Earth (its minimum orbit intersection distance). It frequently passes near Venus, and in about 2,000 years it will begin entering Venus’s Hill sphere (its sphere of gravitational influence). These close encounters gradually alter its orbit, making long-term predictions difficult.
- Discovery date
- 4 April 2025
- Discovery site
- Cerro Tololo Inter-American Observatory
- Discovery instrument
- Dark Energy Camera (DECam) on the 4.0-meter Víctor M. Blanco Telescope
- Diameter
- 0.4 km (0.25 mi)
- Semi-major axis
- 0.462 AU
- Orbital period
- 114.7 days
- Spectral type
- X
Lore & Background
2025 GN1 was discovered on 4 April 2025 by astronomers H. Perkins, T. Murphey, Jan Kleyna, and Robert Weryk using the Dark Energy Camera at Cerro Tololo. Follow-up observations were made by T. Linder and R. Holmes, and the discovery was announced by the Minor Planet Center on 13 April 2025. Later that month, teams led by Scott S. Sheppard and Albino Carbognani noted its orbit closely matched that of 2021 PH27, and observations with the Magellan–Baade and Gemini South telescopes on 14–16 April 2025 confirmed the two asteroids share identical orbits and spectral types.
The asteroid has an X-type spectrum, indicating a neutral to slightly reddish color, and its composition is ambiguous—possibly enstatite, metallic, or organic-rich silicate. Its orbit lies entirely inside Earth's, with a perihelion of 0.136 AU and aphelion of 0.788 AU. It frequently approaches Venus and will begin passing within Venus's Hill sphere in about 2,000 years. Its orbit precesses at 52.6 arcseconds per century due to general relativity.
Reader's Guide
2025 GN1 is significant as a member of a rare asteroid pair with 2021 PH27, the closest orbiting asteroid to the Sun known as of 2026. The pair's identical orbits and spectral types suggest they split from a single parent body over 10,500 years ago. A 2026 study led by Albino Carbognani investigated four possible splitting mechanisms, ruling out tidal disruption by Venus or the Sun because the asteroids did not pass within those bodies' Roche limits in the past 100,000 years. The study found that the perihelion distances of both asteroids dropped to 0.08–0.10 AU during periods 17,000–21,000 and 45,000–48,000 years ago, making thermal fracturing a plausible cause. Alternatively, rotational fissioning due to outgassing or the YORP effect could have formed a binary system that later separated, supported by the pair's mass ratio and primary rotation period matching other binary near-Earth asteroids. The thermal splitting scenario predicts a meteor stream crossing Venus's orbit and asymmetric space weathering, though these remain untested. 2025 GN1's orbit is perturbed by close encounters with Venus, making long-term predictions difficult.
Did You Know?
- The asteroid's orbit precesses at 52.6 arcseconds per century due to general relativity, faster than Mercury's rate.
- 2025 GN1 and 2021 PH27 are believed to have split from a single parent body over 10,500 years ago.
Frequently Asked Questions
What is 2025 GN1?
2025 GN1 is a small near-Earth asteroid whose entire orbit stays inside Earth's path around the Sun, earning it the Atira classification. It measures roughly 0.4 kilometers across and completes one full revolution of the Sun in about 115 days.
How was 2025 GN1 discovered?
Astronomers H. Perkins, T. Murphey, Jan Kleyna, and Robert Weryk first detected the object on 4 April 2025 using the Dark Energy Camera on the 4-meter Víctor M. Blanco Telescope at Cerro Tololo in Chile. The Minor Planet Center officially announced the find on 13 April 2025 after five nights of data.
What makes 2025 GN1's orbit special?
With a semi-major axis of only 0.462 AU, the asteroid never ventures beyond Earth's orbital distance, which is the defining trait of an Atira-type body. It currently stands as the second-closest-orbiting asteroid to the Sun, a distinction it shares with 2021 PH27.
Who carried out the follow-up observations of 2025 GN1?
In the week following the initial detection, T. Linder and R. Holmes tracked the asteroid with a 1.3-meter telescope at the same Cerro Tololo site. Their additional data points helped refine the orbital solution before the MPC announcement.
Why do asteroid fans consider 2025 GN1 noteworthy?
Its fully interior orbit to Earth's path is uncommon among catalogued small bodies, and its modest 0.4-kilometer diameter makes it a genuinely challenging detection. As one of only two known asteroids that circle the Sun closer than Earth does, it occupies a rare slot in the near-Earth object family.
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