February 06, 2023

Using NASA's James Webb Space Telescope, a global team of European astronomers has discovered an asteroid that is about the size of Rome's Colosseum and ranges in length from 300 to 650 feet (100 to 200 meters). The researchers accidentally discovered an asteroid during the calibration of the Mid-InfraRed Instrument (MIRI), which provided the data for their project. The object, which is most likely the tiniest Webb has seen to date, could be an example of an asteroid belt object that is less than 0.6 miles (1 kilometers) long and is situated between Mars and Jupiter. To more fully describe the nature and characteristics of this entity, additional observations are required.

“We — completely unexpectedly — detected a small asteroid in publicly available MIRI calibration observations,” said Thomas Müller, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Germany. “The measurements are some of the first MIRI measurements targeting the ecliptic plane and our work suggests that many new objects will be detected with this instrument,” the researchers write.

These Webb observations, which were reported in the journal Astronomy and Astrophysics, were calibration photos of the main belt asteroid (10920) 1998 BC1, which scientists found in 1998, rather than searches for new asteroids. The calibration team deemed the observations to have failed for technical reasons because of the brightness of the object and an off-center telescope pointing. The observations were made to test the performance of certain of MIRI's filters. Despite this, the researchers used the information from asteroid 10920 to develop and test a new method for estimating an object's size and constraining its orbit. The MIRI observations along with information from ground-based telescopes and the ESA's Gaia mission were combined to show the viability of the method for asteroid 10920.

The team discovered the smaller intrusive object in the same field of view while analyzing the MIRI data. According to the team's findings, the object has an orbit with a very low inclination, measures 100 to 200 meters, and was present during the Webb observations in the inner main-belt region.

If confirmed as a new asteroid discovery, the discovery of this asteroid, which the team believes to be the smallest observed by Webb to date and one of the smallest detected in the main belt, would have significant implications for our understanding of the formation and evolution of the solar system. Because it is challenging to observe small asteroids, their study has lagged behind that of its larger counterparts. Current models anticipate the prevalence of asteroids down to very small sizes. Astronomers will be able to examine asteroids less than one kilometer in size thanks to future dedicated Webb investigations.

Additionally, this finding shows that Webb will be able to accidently assist in the discovery of new asteroids. The team believes that even brief MIRI inspections close to the solar system's plane will occasionally find a few asteroids, the most of which will be unidentified objects.

More positional information with respect to background stars is needed from follow-up investigations to constrain the object's orbit in order to validate that the object observed is a newly discovered asteroid.

Source - NASA