An asteroid will fly closer to Earth than the Moon on Monday

A newly discovered asteroid designated 2026 SA8 will pass closer to Earth than the Moon early Monday, Sept. 28, 2026, coming within about 0.00254 astronomical units — roughly 236,000 miles, or about 0.96 times the distance to the Moon — according to close-approach data published by NASA’s Jet Propulsion Laboratory. The object poses no known threat and will not come this close again for years, but for a few hours it will sit inside the Moon’s own orbit around Earth.

Asteroids pass this close more often than most people realize, and each one still has to be found, measured and cleared individually before scientists can say so with confidence. 2026 SA8 was spotted for the first time barely a week before its closest approach, a timeline that is typical for an object its size rather than unusual.

Objects this small are almost always caught by wide-field, ground-based sky surveys that scan for faint, moving points of light on clear nights and forward promising detections to JPL for orbit calculation. A newly spotted asteroid typically needs several more nights of follow-up tracking before its path is pinned down well enough to rule out any risk, which is why a close approach announced with only a week or two of lead time is the rule for small objects, not the exception.

Asteroid 2026 SA8 surfaced just eight days before its flyby

NASA’s Center for Near-Earth Object Studies, known as CNEOS, logged the first confirmed observation of 2026 SA8 on Sept. 20, 2026, according to the object’s entry in JPL’s Small-Body Database. That gave astronomers just over a week to refine the asteroid’s orbit before it made its closest pass, a routine turnaround for a small object that reflects little sunlight until a survey telescope happens to catch it against the right patch of night sky.

The database record lists the discovery credit under JPL’s own orbit-determination system rather than a single observatory, which is common for objects confirmed and refined through the agency’s automated scanning of incoming survey data rather than a single dedicated sighting.

It crosses inside the Moon’s orbit early Monday

The close-approach data (CAD) API maintained by JPL’s Center for Near-Earth Object Studies puts the moment of closest approach at 2026-Sep-28, 06:45 UTC — 12:45 a.m. Monday on the U.S. East Coast, or 9:45 p.m. Sunday in California — at a distance of 0.00254 astronomical units. NASA and CNEOS routinely express these distances in lunar distances (LD), a unit built on the Moon’s roughly 384,000-kilometer average distance from Earth, according to the agency’s own close-approach reference page; by that measure, 2026 SA8 will pass at about 0.96 LD, just inside the Moon’s orbit.

The asteroid is moving relative to Earth at 6.61 kilometers per second, or nearly 15,000 mph, fast enough to cross the distance between Earth and the Moon in under 17 hours. No estimate of its size or brightness was included in the CAD or database records pulled for this pass, which is common for an object identified so recently.

Its orbit places it in the Apollo family, not the hazard list

JPL classifies 2026 SA8 as an Apollo-type near-Earth object — asteroids whose orbits carry them across Earth’s path but whose average distance from the sun is slightly larger than Earth’s own, according to CNEOS’s explanation of near-Earth object groups. The same page lays out the two-part test CNEOS uses to flag a “potentially hazardous asteroid,” or PHA: an orbit that can bring it within 0.05 astronomical units of Earth, and a size at or above roughly 140 meters across.

The Small-Body Database record explicitly marks 2026 SA8 as not a PHA. Even at under one lunar distance, this particular pass falls outside the criteria that would trigger closer, longer-term monitoring — a distinction that depends on the object’s calculated orbit path over time, not just how close any single flyby happens to bring it.

Flybys this close happen roughly every couple of days

Passes inside the Moon’s orbit are not rare events. NASA’s own near-Earth-asteroid tracker showed 12 objects passing closer than the Moon in a recent 30-day span and 176 over the previous 365 days, according to statistics NASA Science published as of Dec. 3, 2025 — an average of roughly one every other day, most too small and too briefly visible to draw public notice.

That same page put the total catalog of known near-Earth asteroids of all sizes at 39,123 as of its Dec. 3, 2025 snapshot, with scientists estimating thousands more, mostly smaller than 140 meters, still undiscovered. 2026 SA8 is one of the newest entries in that count, added nine days before it briefly slipped closer to Earth than the Moon itself.

CNEOS also assigns each newly confirmed close approach a numerical rarity score once its orbit is well determined, on a scale where a score of zero corresponds to an average of roughly 100 similar encounters worldwide per year, according to NASA’s Center for Near-Earth Object Studies. That framing lines up with the raw counts: an asteroid slipping inside the Moon’s orbit is a routine data point for planetary-defense researchers, not an alarm.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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