The James Webb Space Telescope has discovered 10 times more supernovae in the early universe than previously known. Some of these supernovae are the most distant examples used to measure the expansion rate of the universe.

As the universe expands, light shifts to longer (infrared) wavelengths. This phenomenon is called redshift! Because their light travels great distances and travels for a long time, Webb's powerful and sensitive infrared vision is perfect for observing distant supernovae.

Before Webb, only a few supernovae had been found above redshift 2 (corresponding to the period when the universe was 3.3 billion years old). Now Webb's data includes stars that exploded when the universe was less than 2 billion years young. In total, Webb has discovered about 80 supernovae in a patch of sky the thickness of a grain of rice held at arm's length (circled in green here).

Image description:

A space telescope image showing hundreds of objects of different colours, shapes and sizes against the black background of space. There are small red spots, larger and fuzzy white or bluish masses with bright centres, white, pink or blue disc shapes, prominent spiral structures and barely noticeable speckles. Eighty-three of the small objects in the image are circled in green. Some of the circles are close together, some are far apart and some overlap. There is no obvious pattern to the distribution.