An asteroid roughly the size of the Roman Colosseum — 300 to 650 feet (100 to 200 meters) long — has been discovered by an international team of European astronomers using NASA’s James Webb Space Telescope. The object depicted in this artist’s concept is probably the smallest object Webb has ever observed. The discovery was accidental – the asteroid was found in calibration images of another asteroid. The lucky find shows that Webb was able to detect many such objects.

Telescope discovers an extremely small Main Belt asteroid

An asteroid the size of the Roman Colosseum — 300 to 650 feet (100 to 200 meters) long — has been discovered by an international team of European astronomers using NASA’s James Webb Space Telescope. Their project used calibration data from the Intermediate Infrared Instrument (MIRI), where the team accidentally discovered a transiting asteroid. This object is possibly the smallest object Webb has ever observed, and may be an example of an object less than 0.6 miles (1 kilometer) shorter in the main asteroid belt between Mars and Jupiter. Additional observations are needed to better characterize the nature and properties of this object.

“We discovered a completely unexpected small asteroid in public MIRI calibration observations,” said Thomas Müller, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Germany. “These measurements are among the first MIRI measurements to target the ecliptic plane, and our work shows that many new objects will be discovered with this instrument.”

Webb’s observations published Feb. 6 in the journal Astronomy and Astrophysics, was not designed to hunt for new asteroids—in fact, they were calibration images of 1998 BC of the main belt asteroid (10920) that astronomers discovered in 1998. Observations were made to test the performance of some MIRI filters, but the calibration team thought they failed for technical reasons due to the brightness of the target and the offset telescope. Despite this, data on asteroid 10920 was used by the team to create and test a new technique for limiting the object’s orbit and estimating its size. The validity of the method was demonstrated for asteroid 10920 using MIRI observations combined with data from ground-based telescopes and ESA. Gaia mission.

Analyzing the MIRI data, the team found a smaller intruder in the same field of view. The team’s results show that the object is 100-200 meters in size, is in a very low-inclination orbit, and was located in the interior of the main belt during Webb’s observations.

“Our results show that even ‘failed’ Webb observations can be scientifically useful if you have the right mindset and a bit of luck,” Muller said. “Our detection lies in the main asteroid belt, but Webb’s incredible sensitivity made it possible to see this nearly 100-metre object from more than 100 million kilometers away.”

If the discovery of this asteroid, which the team suspects is the smallest Webb has ever observed and one of the smallest found in the main belt, is confirmed as a new asteroid discovery, it will have important implications for our understanding of formation and evolution. Solar system. Current models predict asteroid formation to very small sizes, but small asteroids have been studied in less detail than their larger counterparts due to the difficulty of observing these objects. Webb’s future special observations will allow astronomers to study asteroids smaller than 1 kilometer.

At most, this result suggests that Webb may inadvertently contribute to the discovery of new asteroids. The team suspects that even brief MIRI observations near the plane of the Solar System will always contain a few asteroids, most of which will be unknown objects. To confirm that the detected object is a newly discovered asteroid, additional data on its position relative to background stars from further surveys to constrain the object’s orbit are needed.

“This is a fantastic result that highlights MIRI’s ability to accidentally detect an asteroid of previously undetectable size in the main belt,” said Brian Holler, a Webb research fellow at the Space Telescope Science Institute in Baltimore, Maryland. “Repetition of these observations is in the planning process, and we expect entirely new asteroids to disrupt these images.”