James Webb Telescope Spotted Smallest Main Belt Asteroid Yet

An asteroid the size of Rome’s Colosseum and ranging in length from 300 to 650 feet has been found by a multinational team of astronomers from Europe using NASA’s James Webb Space Telescope (100 to 200 metres). The Mid-InfraRed Instrument (MIRI), which gave the data for their investigation, was being calibrated when the researchers unintentionally came across an asteroid.

It is most certainly the smallest object Webb has ever seen, and it could be an example of an asteroid belt object that is less than 0.6 miles (1 kilometre) long and located between Mars and Jupiter.

Sole Purpose Of The Inspection

To more fully explain this entity’s nature and characteristics, more observations are required. Considering that these data are some of the first MIRI measurements to focus on the ecliptic plane, our research suggests that this instrument will be able to discover a large number of novel objects.

These Webb observations, which were reported in the journal Astronomy and Astrophysics, weren’t made with the intention of looking for new asteroids; rather, they were calibration photographs of the main belt asteroid (10920) 1998 BC1, which scientists found in 1998.

The inspection was made to assess how well certain of MIRI’s filters worked, but the calibration team believed they had failed due to technical issues caused by the target’s brightness and an off-center telescope pointing.

Researchers Findings

In spite of this, the team’s work on asteroid 10920 allowed them to develop and test a new method for estimating an object’s size and constraining its orbit. With the help of MIRI observations, data from ground-based telescopes, and the ESA’s Gaia mission, the validity of the method was proven for asteroid 10920.

During the process of analysing the MIRI data, the team discovered the smaller encroachment in the same field of view. The team’s findings show the object has a diameter of 100–200 metres, a very low orbital inclination, and was situated in the inner main-belt region during the Webb observations.

Our findings demonstrate that, with the correct attitude and a little bit of luck, even “failed” Webb observations can be scientifically valuable, Müller added. Our discovery is located in the main asteroid belt, yet Webb’s extraordinary sensitivity allowed us to observe this about 100-meter-diameter rock from a distance of more than 100 million kilometres.

Webb Being An Aid In Earthing Further Planetoids

If verified as a new asteroid discovery, the team’s discovery of this asteroid, which they believe to be one of the tiniest ever found in the main belt and the smallest ever seen by Webb, will have significant aftermath for our knowledge of the genesis and evolution of the solar system.

Small asteroids have been researched in less depth than their larger counterparts due to the difficulty of spotting these objects, despite the fact that current models anticipate the presence of asteroids down to very small sizes. Astronomers will be able to investigate asteroids under 1 km in size with the help of future dedicated Webb observations.

Additionally, this finding raises the possibility that Webb will unintentionally aid in the discovery of further asteroids. The team hypothesises that at least a few asteroids, the majority of which will be unidentified objects, will always be present in even brief MIRI observations close to the solar system’s plane.


More positional information in relation to background stars from follow-up investigations is necessary to restrict the object’s orbit and establish that the item spotted is a freshly discovered asteroid.

Bryan Holler, a Webb support scientist at the Space Telescope Science Institute in Baltimore, Maryland, said, “This is a remarkable result that illustrates the capability of MIRI to accidentally discover a size of asteroid in the main belt that was previously undetectable. “We fully expect new asteroid interlopers in those images,” the authors write. “Repeats of these observations are currently scheduled.”

Leave a Comment