An asteroid discovered days ago will narrowly miss Earth

We may not notice them, but it's not usual for a bus-size asteroid to pass through our earthly neighborhood several times every year. JPL-Caltech/NASA via CNN Newsource

An asteroid roughly the size of one to two school buses will fly by Earth Monday, coming as close as 91,593 kilometres (56,913 miles), according to the European Space Agency — equivalent to about one quarter of the distance between Earth and the moon.

Astronomers at the Mount Lemmon Survey in Tucson, Arizona, discovered the asteroid on May 10 and named it 2026JH2. The object belongs to a class of asteroids called Apollo, which orbit the sun on trajectories that intersect with Earth’s own orbit around the sun.

At its closest pass, 2026JH2 will be about 24 per cent of the average distance between Earth and the moon, and about two and a half times the distance at which hundreds of geosynchronous satellites orbit, providing services such as telecommunications and weather forecasts. The close pass is expected to occur on Monday just before 6 p.m. ET, according to NASA’s JPL Small-Body Database.

Despite the proximity, the space rock poses no danger, according to Richard Binzel, a professor of planetary sciences at the Massachusetts Institute of Technology and the inventor of the Torino Scale, a tool for categorizing potential collisions of space objects with Earth.

“2026JH2 will pass safely by the Earth,” he said in an email. “This is actually a rather normal occurrence, car-sized objects pass between the Earth and the Moon every week. At the size of a school bus, these pass through our neighbourhood several times per year. We are only recently developing surveys that are sensitive enough to see them,” he added, noting that before these surveys, objects of this kind would simply zoom by completely unnoticed.

Exact size unknown

The asteroid originates from the asteroid belt, an area between Mars and Jupiter, Binzel explained. “Occasional collisions in the asteroid belt, plus gravitational tugs by Jupiter, can send small asteroids into Earth’s vicinity. This fact has been known for many decades and many thousands of asteroids that can pass near the Earth are already known.”

Even though astronomers have directly observed the object hurtling toward Earth, its exact size is unknown. The uncertainty is due to the fact that when an optical telescope sees a new object, the only information it gathers is the object’s luminosity in visible light. There is no way to know how much light the object absorbs or reflects, according to Patrick Michel, an astrophysicist and director of research at the National Centre for Scientific Research in France.

“Thus, at the same luminosity, an object can be bigger and darker, or smaller and more reflective,” he said in an email. “To know the size, we would need observations in the infrared, because the luminosity in the infrared is directly proportional to the size. But such observations are more difficult to do from the Earth and are not used to discover new objects.”

Based on assumptions about how much light is reflected, 2026JH2 is currently estimated to be between 15 and 30 metres (50 and 100 feet) in diametre. At the smaller end of that range, Michel said, it would be similar in size to a bolide, or fireball, that exploded in the atmosphere over the city of Chelyabinsk, Russia, in 2013, shattering windows and injuring 1,000 people. At the highest end of the range, it would be closer in size to an object that exploded near the Podkamennaya Tunguska River in Siberia in 1908, which pulverized large swaths of forest. Unlike both of these objects, however, 2026JH2 will not even enter the atmosphere, so there is no risk it will explode.

Although the distance at which the asteroid will pass seems very close, it is still “far enough that there is absolutely nothing to worry about,” Michel said. But he noted that predicting 2026JH2’s future trajectory is difficult, and we can’t rule out that it might eventually be on a collision course with Earth. “The good news is that so far, no asteroid that we know of poses a risk for the timescale of our predictions, which is about a century on average,” he added.

Waiting for Apophis

An object at least 10 times bigger than 2026JH2, called Apophis, will pass much closer to Earth, at a projected 32,000 kilometres (20,000 miles), on April 13, 2029, “Yet, we are not worried at all, and on the contrary very excited,” Michel said. “Such a close approach of such a big object occurs only once in a few thousands of years and its light will even be visible with the naked eye in the night sky across Europe, Africa and part of the middle East.”

By contrast, during its closest approach, 2026JH2 will only be detectable with small telescopes at dark sites, but it will remain 100 times too faint to be seen by the human eye, according to Jean-Luc Margot, a professor of Earth, planetary and space sciences at the University of California, Los Angeles.

Part of the reason we don’t have more detailed information about the asteroid, he added in an email, is that our planetary radar capabilities are currently degraded. “The Arecibo telescope collapsed in 2020 and NASA’s Goldstone antenna is down for major repairs for an extended period of time. Without radar data, we are less capable of assessing the impact risk and we are more vulnerable to the impact hazard.”

A partial livestream of the close pass will be provided by the Virtual Telescope Project using telescopes in Italy, starting at 3:45 p.m. ET, and lasting until the object is no longer visible from that location.

So far, astronomers have observed only about 1 per cent of the near-Earth asteroids in the same size range as 2026JH2, Margot said, and therefore “it’s not surprising that this object was discovered only a few days before its closest approach to Earth, when it became bright enough to be picked up by asteroid detection surveys.”

He added that it’s concerning that we do not have complete knowledge about the population of near-Earth objects but noted that space agencies are now actively funding discovery surveys to improve our inventory of potentially hazardous asteroids.

Jacopo Prisco, CNN