Bus-sized asteroid passes safely near Earth at quarter lunar distance

On Monday evening, just before eleven o'clock in Portugal, a space rock the size of a bus or two will slip past Earth at a distance of roughly 91,600 kilometers. That sounds far until you learn it's only a quarter of the way to the Moon—close enough that it will pass nearer to us than the satellites that beam our weather forecasts and phone calls across continents. The asteroid, designated 2026JH2, was discovered only eight days earlier by astronomers at Mount Lemmon Survey in Arizona, on May 10th. It belongs to a class of asteroids called Apollo objects, whose orbits cross Earth's path around the Sun. Yet despite the proximity, there is no danger.

Richard Binzel, a planetary scientist at MIT and creator of the Torino Scale—the tool used to assess collision risk from space objects—offers perspective on what might otherwise sound alarming. Close passes like this one are routine, he explains. Car-sized objects slip between Earth and the Moon every week. Bus-sized asteroids traverse our neighborhood several times a year. The reason we're only now learning about them is that our detection systems have only recently become sensitive enough to catch them. Before these instruments existed, such visitors passed completely unnoticed.

The asteroid originated in the belt between Mars and Jupiter, where occasional collisions and Jupiter's gravitational pull occasionally send smaller rocks toward Earth's neighborhood. Thousands of such asteroids have already been catalogued. Yet despite direct observation of 2026JH2 as it approaches, its exact size remains uncertain. When an optical telescope first detects a new object, it captures only one piece of information: how much visible light the object reflects or absorbs. A rock could be large and dark, or small and highly reflective, and appear identical through a standard telescope. To know the true size, astronomers would need infrared observations, which directly correlate to mass. But such measurements are difficult to obtain from Earth and are not used in the initial discovery process. Based on estimates of reflected light, scientists currently calculate the asteroid measures between 15 and 30 meters across.

At the smaller end of that range, the object would resemble the fireball that exploded over Chelyabinsk, Russia, in 2013, shattering windows and injuring roughly a thousand people. At the larger end, it would approach the size of the object that detonated near the Tunguska River in Siberia in 1908, flattening vast stretches of forest. The crucial difference: 2026JH2 will not enter the atmosphere. It will pass safely through the void. Patrick Michel, an astrophysicist and research director at France's National Center for Scientific Research, acknowledges that while the distance seems razor-thin, it remains "sufficiently large that there is absolutely nothing to worry about." He adds, however, that predicting the asteroid's future trajectory is difficult, and a collision cannot be ruled out entirely for some distant time. The reassuring news is that among all known asteroids, none pose a risk within the roughly century-long horizon of current predictions.

The real excitement among astronomers centers on a different visitor. Apophis, an object at least ten times larger than 2026JH2, will pass even closer to Earth—about 32,000 kilometers—on April 13, 2029. Michel expresses not concern but enthusiasm. Such a close approach by such a large object occurs only once every several thousand years. Its brightness will be visible to the naked eye across Europe, Africa, and parts of the Middle East. By contrast, 2026JH2 will require a small telescope in a dark location to observe; it will be one hundred times too faint for unaided human eyes.

The scarcity of detailed information about 2026JH2 reflects a broader vulnerability. Planetary radar capabilities have diminished. The Arecibo telescope collapsed in 2020, and NASA's Goldstone antenna has been offline for extensive repairs. Without radar data, scientists have less capacity to assess impact risk and face greater exposure to collision danger. Jean-Luc Margot, a professor of Earth, planetary, and space sciences at UCLA, notes that astronomers have observed only about one percent of near-Earth asteroids in the same size range as 2026JH2. It is therefore unsurprising that this object was discovered only days before its closest approach, when it finally became bright enough for detection systems to catch it. While Margot finds it concerning that a complete inventory of near-Earth objects does not yet exist, he notes that space agencies are now actively funding detection programs to improve the catalog of potentially hazardous asteroids. The Virtual Telescope Project will stream the passage through Italian telescopes beginning at 8:45 p.m. Portugal time, continuing until the asteroid passes beyond view from that location.