This asteroid - between 100 and 200 meters wide - is the smallest object observed for the moment using the space telescope, NASA said on Monday.

It was "detected by chance" by European astronomers, the US space agency added in a statement, adding that further observations would be needed to better characterize its nature and properties.

"The incredible sensitivity of the (James) Webb telescope made it possible to observe this object about 100 meters (wide) from a distance of more than one hundred million kilometers," said Thomas Muller, astronomer at the Max Planck Institute in Germany.

The discovery of this star occurred during the calibration of the MIRI infrared observation tool, the result of a collaboration between Europeans and Americans.

James Webb, launched into space by an Ariane 5 rocket, has been operational since July 2022. It is the most powerful space telescope ever built and has collected a large amount of data and captured breathtaking images.

In project since the 1990s, it is stationed 1.5 million kilometers from Earth, with enough fuel to operate for 20 years.

One of the missions of James Webb, a jewel of engineering worth 10 billion dollars, is the exploration of the very young Universe.

It also aims to search for exoplanets.

The telescope was not designed to search for small objects such as this new asteroid, but Mr Muller said his discovery "suggests that many new objects will be detected with this instrument".

© 2023 AFP