James Webb and Hubble joined together to photograph DART's collision

James Webb and Hubble joined together to photograph DART's collision

For the first time, James Webb and Hubble simultaneously observed the same target: the asteroid Dimorphos before and after the fall of the NASA DART probe during the first-ever planetary defense test.

For the first time in the history of James Webb and Hubble, they simultaneously observed the same celestial object, an asteroid called Dimorphos, on which NASA DART intentionally landed on the night of 26 to 27 September as the world's first planetary defense test.

The joint observations of Webba and Hubble will allow scientists to study the nature of the surface of Dimorphos, to determine how much material was released as a result of the impact and how quickly it happened. Two space telescopes that cover the ultraviolet, visible, near and medium infrared range of wave lengths will provide important clues about the distribution of debris from the impact. This will help researchers to understand how effective such a kinetic shock can be to alter the orbit of an asteroid.

Webb: collision site before and after the accident

Webb observed the area of Dimorphos, where the DART probe was expected to strike before the crash occurred. Then the telescope continued several observations in the following hours.

Because of the speed at which the asteroid travels across the sky, Webb's team has worked for several weeks to turn on and test Webb's tracking technique, which involves tracking very small celestial bodies moving more than three times the speed limit set for JWST, but in the end, the largest space telescope ever built by a person has done so: he has taken a total of 10 pictures within five hours.

In the coming months, the asteroid Dimorphos will also be observed by means of a spectrograph of the medium infrared range . Spectroscopic data will provide information on the chemical composition of the asteroid.

Hubble: expansion of debris cloud

Hubble was also able to observe the asteroid before the impact, and then again 15 minutes after DART encountered the surface of Dimorphos. Images from wide-angle camera 3 show the crash in visible light. A total of 45 images are currently available.

The debris emitted from the impact looks like the rays emanating from the asteroid's body. Some seem slightly curved, but astronomers need to take a closer look to determine what that might mean. According to Hubble, astronomers estimated that the brightness of Didimos, the main pair of asteroids to which DART was headed, has tripled after the impact. Particularly curious is the fact that brightness remained stable even eight hours after the impact.

Over the next three weeks, Hubble will target Dimorphos ten more times, and these regular and relatively long-term observations, as the abandoned cloud expands and disappears, will provide a more comprehensive picture of the expansion of the cloud from discharge to extinction.

Future ESA mission Hera

The ESA Hera mission, scheduled for launch in October 2024, will conduct a detailed post-crash study of the asteroid Dimorphos.

NASA's DART and Hera ESA missions are good examples of what international cooperation can achieve. Like Webb and Hubble, these two missions are supported by different teams of scientists and astronomers who, working together, can help us untangle the fabric of space near and far away, more than ever before.