Rings, spokes and a dusty core: NASA’s James Webb reveals story of Cartwheel Galaxy’s violent past

This image of the Cartwheel and its companion galaxies is a composite from Webb’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI), which reveals details that are difficult to see in the individual images alone. (Image: NASA, ESA, CSA, STScI, Webb ERO Production Team)

The James Webb Space Telescope has offered a striking new portrait of the Cartwheel Galaxy, showing fresh detail of star formation and a central black hole.

What makes the Cartwheel Galaxy so unusual?
The Cartwheel lies about 500 million light-years away in Sculptor. Its wagon-wheel configuration developed after a brutal impact with a smaller galaxy. The collision recast its shape, creating two expanding rings. They radiate outward like ripples in water, making the galaxy its unique "ring" type.

What secrets did Webb reveal?

The central core is filled with scorching dust and giant clusters of new stars. The outer ring, stretching out for 440 million years, exhibits vigorous star formation and exploding supernovae.

Webb’s infrared vision pierces thick dust, capturing details that earlier Hubble images missed. The Near-Infrared Camera shows countless blue dots, each a star or a pocket of star formation. It also distinguishes between older stars in the centre and younger populations further out.

How does MIRI add to this picture?
The Mid-Infrared Instrument highlights regions rich in hydrocarbons, silicates and other compounds. These appear in red, tracing spiral spokes that form the galaxy’s skeleton. Such structures were faintly seen by Hubble in 2018 but now appear sharper and more extensive in Webb’s view.

This image from Webb’s Mid-Infrared Instrument (MIRI) shows a group of galaxies, including a large distorted ring-shaped galaxy known as the Cartwheel. (Image: NASA, ESA, CSA, STScI, Webb ERO Production Team)

Why are these observations important?
Astronomers think the Cartwheel used to be a typical spiral galaxy like the Milky Way. Webb captures it mid-metamorphosis, suspended between its tumultuous past and murky future. The telescope not only discloses its present-day appearances but also offers insight into how the galaxy has changed over billions of years.