The James Webb Space Telescope sits silently in the chilly darkness a million miles away, far beyond Earth’s atmosphere. On most days, its eyes stray to ancient galaxies, faint red glows from the early universe—the kind of far-off light that left its source before Earth even formed. However, Webb sometimes has to do something far less poetic. It must pursue rocks.
One of those occasions was when Webb was asked by scientists to monitor an asteroid that was speeding across the sky. It sounded ordinary on paper. In reality, it was anything but. Compared to tracking a piece of stone traveling across the telescope’s field of view at tens of thousands of miles per hour, observing a far-off galaxy is simple.
| Category | Details |
|---|---|
| Observatory Name | James Webb Space Telescope (JWST) |
| Developed By | NASA, ESA, CSA |
| Launch Date | December 25, 2021 |
| Primary Mission | Observe early universe, galaxies, stars, exoplanets |
| Mirror Size | 6.5 meters (18 gold-coated segments) |
| Orbit Location | Sun–Earth L2 point (about 1.5 million km from Earth) |
| Key Instruments | NIRCam, NIRSpec, MIRI, FGS/NIRISS |
| Notable Capability | Infrared observation of distant objects and moving targets |
| Planetary Defense Role | Can track asteroids and analyze composition |
| Reference | https://science.nasa.gov/mission/webb |
Engineers at NASA’s Goddard Space Flight Center were aware of the danger from the control rooms. Webb was primarily designed to observe objects in deep space that hardly move from one night to the next. Asteroids are not the same. They cause the telescope to constantly adjust while maintaining perfect mirror alignment as they streak across the sky. An instrument intended for delicate precision may be stressed by that type of movement.
As you listen to the scientists discuss it, you get the impression that they were both thrilled and a little nervous.
As a kind of practice for tracking potentially dangerous objects in the future, the test involved tracking a known asteroid inside our solar system. NASA chose asteroid 6841. The main-belt item Tenzing bears the name of mountaineer Tenzing Norgay. The symbolism seemed deliberate. At one point, it seemed impossible to climb Everest. The most sensitive space telescope ever constructed was also guided toward a moving rock.
As the asteroid moved through the darkness, infrared sensors inside Webb’s instruments started to record it. In order to maintain the extremely low temperatures necessary for infrared observation, the telescope had to slowly rotate in order to change its orientation. Engineers were concerned about minute distortions in the alignment of the mirror. The data could be distorted by even slight temperature changes.
Surprisingly sharp images of a faint moving dot against a velvet black background appeared on the screens. Not cinematic, not dramatic. Just a precise infrared light trail. Yet for the scientists watching, it meant something larger: Webb could track objects moving through our own solar system, not just galaxies billions of light-years away.
Humanity is reminded of its vulnerability by asteroids. The extinction of the dinosaurs is the most famous example, but smaller impacts have happened in recent history. In 2013, a Russian city’s windows were broken by the Chelyabinsk meteor. Massive amounts of energy can be carried by even small space rocks.
Therefore, the term “potentially hazardous asteroids” tends to carry a lot of weight when astronomers discuss them.
Webb-style telescopes might be incorporated into Earth’s planetary defense plan. The heat signature of asteroids, which can provide information about their size, shape, and even composition, can be measured by the telescope thanks to its infrared vision. That information is important. The behavior of a dense metallic asteroid differs greatly from that of a dark carbon asteroid.
When NASA purposefully crashed a spacecraft into the asteroid moonlet Dimorphos, Webb and the Hubble Space Telescope collaborated to monitor the DART mission. Plumes of debris were launched into space by the collision, and they could be seen as tiny dust spikes moving away from the impact site. Despite the fact that the event took place millions of miles away, it felt strangely cinematic to watch those pictures develop.
Scientists were able to comprehend how asteroid deflection might function in an actual emergency thanks to the data.
Naturally, Webb resides in a hazardous area. There is more than just space. Like invisible bullets, micrometeoroids speed across the solar system. One of those tiny pieces struck Webb’s mirror in 2022, slightly denting one of its gold-plated sections. The incident was a silent reminder of the dangers, but engineers managed to correct the mirror alignment and continue the mission. It seems almost unreal to watch a delicate $10 billion telescope function in that setting.
The entire endeavor has an oddly human quality. Sitting in dark control rooms are groups of astronomers. Desks with coffee cups. screens with dim light points shining on them. A telescope tracks a moving rock in the dark somewhere far beyond Earth, while everyday life—traffic, weather, and people walking dogs—continues outside the building.
The engineers who created Webb’s tracking system are deserving of quiet appreciation. The telescope can now follow objects moving several times faster than originally planned. The improvement was not insignificant. Months of preparation, testing, and minor tweaks to the observatory’s guidance algorithms were needed.
Even the most sophisticated technology can be humbled by space. Asteroids are still unpredictable, and early detection is just one aspect of the problem. If the need ever arises, deflecting one will require new spacecraft designs, international cooperation, and a good deal of luck.
However, there is an odd sense of comfort when you watch Webb chase those far-off rocks.
Even though humans have no control over the universe, they are starting to pay closer attention to it. And there are moments when it seems like the first step to survival.