This is the 107th known asteroid to fly past Earth within 1 lunar distance since the start of the year and the 16th so far this month. The only month we discovered more
2025 SU4 is belongs to Aten group of asteroids and has an estimated diameter between 2 and 5 m (6.6–16.4 feet).
The object was first observed at Mt. Lemmon Survey, Arizona on September 23 — some 27 hours before close approach. It flew past us at a speed (relative to Earth) of 9.18 km/s at 08:34 UTC.
This is the 4th closest asteroid flyby of the year, after 2025 BP6 on January 26 at 0.025 LD, 2025 OS on July 19 at 0.027 LD, and 2025 FY6 on March 23 at 0.057 LD. All of these objects had diameters between 1.1 and 6 m (3.6–19.7 feet).
With a distance of 0.058 LD, 2025 SU4 tied with 2025 PF2, which passed at the same distance on August 15 and measured 2.5 to 5.6 m (8.2–18.4 feet) in diameter.
If 2025 SU4 had been on a collision course with Earth, its small size means it would have disintegrated high in the atmosphere. The resulting airburst would likely produce a bright fireball, but no ground damage.
Objects of this scale enter Earth’s atmosphere several times per year, typically over oceans or remote areas, and pose no significant hazard.
The main outcome would be a short-lived atmospheric event, potentially detectable by infrasound sensors and satellites.
References:
1 Asteroid 2025 SU4 – Minor Planet Center – Accessed September 24, 2025
2 Asteroid 2025 SU4 – NASA/CNEOS – Accessed September 24, 2025