The James Webb Space Telescope has observed the chaos of the Cartwheel galaxy, revealing new details about star formation and the galaxy’s central black hole.
Webb’s powerful infrared gaze produced this detailed image of Cartwheel (Cart wheel in its English name) and two smaller companion galaxies against a backdrop of many other galaxies. This image offers a new insight into how Cartwheel has changed over billions of years.
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Located about 500 million light-years away in the constellation Sculptor, this galaxy is a rare sight.
Located about 500 million light-years away in the constellation Sculptor, this galaxy is a rare sight. Its appearance, much like that of a cartwheel, is the result of an intense event: a high-speed collision between a large spiral galaxy and a smaller galaxy not seen in this image. Collisions of galactic proportions cause a cascade of different and smaller events between the galaxies involved; The cartwheel is no exception.
The collision notably affected the shape and structure of the galaxy. Cartwheel sports two rings: a shiny inner ring and a colorful ring that surrounds it. These two rings extend outward from the center of the collision, like ripples in a pond after the throwing of a stone. Because of these distinctive features, astronomers call it a “ring galaxy,” a less common structure than spiral galaxies like our Milky Way, NASA reports.
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The bright core contains a huge amount of hot dust, and the brightest areas are home to gigantic clusters of young stars. On the other hand, the outer ring, which has been stretching for about 440 million years, is dominated by star formation and supernovae. As this ring expands, it collides with the surrounding gas and triggers star formation.
Other telescopes, including the Hubble Space Telescope, have examined Cartwheel before. But the spectacular galaxy has been shrouded in mystery, perhaps quite literally, given how much dust obscures the view. Webb, with his ability to detect infrared light, is now uncovering new information about the nature of the galaxy.
Webb’s observations underscore that Cartwheel is in a very transitional phase.
The Near Infrared Camera (NIRCam), Webb’s primary imager, peers into the near infrared range of 0.6 to 5 microns, seeing crucial wavelengths of light that can reveal even more stars than visible light on Earth. This is because young stars, many of which form in the outer ring, are less obscured by the presence of dust when viewed in infrared light.
In this image, the NIRCam data is colored blue, orange, and yellow. The galaxy shows many individual blue dots, which are individual stars or hotspots of star formation. NIRCam also reveals the difference between the smooth distribution or shape of older star populations and dense dust in the core versus the clumped shapes associated with younger star populations outside.
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However, learning finer details about the dust inhabiting the galaxy requires Webb’s Mid-Infrared Instrument (MIRI). MIRI data is colored red in this composite image. It reveals interior regions rich in hydrocarbons and other chemical compounds, as well as silicate dust, like much of the dust on Earth. These regions form a series of spiral rays that essentially form the backbone of the galaxy. These rays are evident in earlier Hubble observations published in 2018, but become much more prominent in this Webb image.
Webb’s observations underscore that Cartwheel is in a very transitional phase. The galaxy, which was presumably a normal spiral galaxy like the Milky Way before its collision, will continue to transform. While Webb gives us insight into the current state of this galaxy, he also gives insight into what happened to this galaxy in the past and how it will evolve into the future.