Mountain-sized asteroid 1999 AN10 will soar past Earth on August 7, 2027, coming within roughly one lunar distance while posing no impact threat to our planet.
The 2027 Flyby Metrics
The space rock measures roughly 800 to 1,800 meters wide, equating to about 0.5 to 1.1 miles across. NASA labels the object as potentially hazardous due to its massive scale and close orbital approach, though current telemetry confirms zero chance of a collision during this transit.
The closest approach will occur at 7:12:05 UTC on August 7, 2027. For viewers in the Americas, that translates to 2:12:05 am CDT on August 7.
Separation at peak approach will measure approximately 389,855 kilometers, or 242,240 miles. That distance is roughly the same as the moon’s distance from Earth.
Observing the Night Sky
Observers across North and South America will be able to spot the asteroid using standard binoculars as it glides overhead. Peak brightness will reach approximately magnitude 7.3.
Overnight on August 7, 2027, the trajectory will carry the asteroid directly through the constellations Taurus, Aries, Pisces, and Pegasus. Simulations by Tony Dunn track this exact celestial pathway.
Despite passing at a distance roughly equivalent to one lunar separation, the asteroid will completely miss the moon. The closest distance between 1999 AN10 and the moon will measure 763,391 km, or 474,349 miles. The moon will sit on the opposite side of Earth during the transit.
Astronomers Discovered Asteroid's Path
Astronomers first discovered 1999 AN10 on January 13, 1999, at the Lincoln Laboratory Experimental Test Site in New Mexico. The body is classified as an Apollo-class asteroid, meaning its elongated elliptical path crosses Earth’s orbit around the sun.
The orbital period takes 643 days to complete a single revolution. This trajectory swings the asteroid from well inside Earth’s orbital path out beyond the orbit of Mars.
NASA monitors approximately 2,500 known potentially hazardous asteroids. Researchers estimate this catalog represents roughly half of the total population, though 90% of the largest objects in this category have already been identified.
Comparison With Other Near-Earth Objects
Other notable near-Earth objects share similar orbital characteristics and close encounter schedules in the coming years. 99942 Apophis will pass roughly 32,000 km above Earth’s surface on April 13, 2029, coming closer than many geostationary satellites. Additional observations have ruled out an impact risk for Apophis for at least a century, and NASA’s OSIRIS-APEX spacecraft is scheduled to study it after the encounter.
Meanwhile, asteroid 101955 Bennu carries a potential impact date of September 24, 2182, with impact odds calculated at roughly 1 in 2,700 by NASA’s 2021 orbital analysis. NASA’s OSIRIS-REx mission collected a physical sample from Bennu and returned it to Earth in 2023.
Additional close flybys include 2001 WN5, which will pass 248,700 km from Earth’s center on June 26, 2028, reaching a peak magnitude of 6.7. Asteroid 1997 XF11 will pass at a distance of about 929,000 km on October 26, 2028.
Next Milestones
Astronomers continue to refine orbital tracks for all cataloged near-Earth objects ahead of the 2027 approach. The next major observational milestone arrives with the closest approach of 1999 AN10 on August 7, 2027.
