- Jonathan Amos
- Science Correspondent, BBC
7 hours
image source, ESA
A small rock fragment has struck the main mirror of the new James Webb Space Telescope. The damage inflicted by the dust-sized micrometeorite is having a discernible effect on the instrument’s data, but is not expected to limit overall mission performance. .The James Webb was launched in December to replace the revolutionary – but already aging – Hubble space telescope. Astronomers are scheduled to release their first images of the cosmos on July 12. The US space agency (NASA) said that these images they will be no less impressive for what has just happened.
The incident appears to have occurred sometime between May 23 and 25. Analysis indicates that the mirror segment known as C3 – one of 18 beryllium-gold tiles that make up the 6.5m wide primary reflector of the telescope – suffered the impact of this rocky particle.
The speed at which objects move in space means that even the smallest particles can give off a lot of energy when colliding with another object. Webb has been hit five times, with this latest event being the most significant.
The Webb has an open design; its mirrors are not protected by the kind of tubular baffle seen on other space telescopes, such as Hubble. Instead, the reflectors sit behind a giant sunshield that allows them to maintain cool, stable temperatures needed to detect infrared light.
predicted accidents
The possibility of micrometeorite impacts was anticipated and these types of contingencies were incorporated into the choice of materials, the construction of components and the different modes of operation of the telescope.
“We always knew that the Webb would have to withstand the space environment, which includes harsh ultraviolet light and charged particles from the Sun, cosmic rays from extraneous sources in the galaxy, and occasional impacts from micrometeoroids within our Solar System,” said Paul. Geithner, deputy technical project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We have designed and built the Webb with a performance margin – optical, thermal, electrical and mechanical – to ensure that it can perform its ambitious scientific mission even following many years in space.
Engineers will adjust the position of the affected mirror segment to cancel out some of the distortion introduced, but they won’t be able to completely eliminate it. Webb is currently collecting observations of the Universe, near and far, to demonstrate its capabilities. Astronomers will present these images to the world next month. In the longer term, scientists intend to use the Webb to try to see the first stars that lit up the cosmos more than 13.5 billion years ago. They will also train the telescope’s large “eye” on the atmospheres of distant planets to see if those worlds might be habitable.
Remember that you can receive notifications from BBC World. Download the new version of our app and activate it so you don’t miss out on our best content.