On August 21, 2019, astronomers confirmed that an asteroid passed close to Earth. The object—identified by survey teams and tracked by NASA’s Center for Near-Earth Object Studies (CNEOS) and partner observatories—made a near-Earth close approach on that date without impacting the planet. Scientists characterized the event as an opportunity to refine the asteroid’s orbit and to test tracking and characterization capabilities. Detection and tracking The asteroid was discovered and reported by routine sky surveys that scan for near-Earth objects (NEOs). After initial detection, follow-up observations from ground-based telescopes allowed orbit determinations sufficient to project a close approach for August 21, 2019. NASA’s CNEOS maintains publicly available Sentry and Scout systems that assess impact risk; in this case the object was tracked well enough before and after the close approach to rule out an imminent impact. Close-approach distance and size estimates Publicly available summaries for NEO close approaches typically report distance in terms of lunar distances (the average Earth–Moon separation) or kilometers, and list estimated size ranges based on observed brightness and assumed reflectivity (albedo). For many small asteroids, those size estimates can carry substantial uncertainty until more detailed observations (radar or thermal infrared) are obtained. In this event, the object passed within a distance commonly described as “close” in astronomical terms but did not enter Earth’s atmosphere as an impactor. Scientific value Close passes by small asteroids provide multiple scientific and practical benefits: they allow astronomers to improve orbital solutions, reduce uncertainties in future trajectory predictions, and sometimes enable radar observations that yield size, shape, and rotation data. They also serve to validate detection systems and international reporting protocols among survey teams and space agencies. Public risk and communications Although close approaches can sound alarming to non-specialists, NASA and other agencies maintain a tiered public communication practice: objects with credible, non-negligible impact probabilities are highlighted and monitored closely; objects confirmed to pose no impact threat are reported as such. For the August 21, 2019 pass, agencies indicated no impact occurred and no hazardous effects were observed. Context Earth regularly experiences close approaches by small asteroids—hundreds to thousands of meters to tens of meters in size—many of which pass well outside the atmosphere. Larger, potentially hazardous asteroids are cataloged and tracked over long intervals to anticipate future risks. The 2019 close approach fits into routine near-Earth object monitoring efforts that have increased in capability over the past two decades through improvements in survey telescopes, international coordination, and dedicated analysis centers. Uncertainties and limitations Details such as precise size, shape, rotation state, and exact close-approach distance can vary in precision depending on how much follow-up data were obtained. Unless radar or space-based thermal observations were taken for a specific object, size estimates often remain ranges rather than exact measurements. Reporting agencies publish updated orbital elements and uncertainty estimates as further observations refine the record. Summary On August 21, 2019, a near-Earth asteroid passed close enough to warrant tracking and public reporting but did not impact Earth. The event was used by astronomers to improve orbital knowledge and demonstrates the routine functioning of NEO detection and monitoring systems.