WEBB’S MIRI captured the galaxy’s complex structure

Webb’s Icy instrument reveals complex structures.


The Mid-InfraRed Instrument (MIRI), which is mounted on the NASA/ESA/CSA James Webb Space Telescope, captured an image of the spiral galaxy IC 5332 in unprecedented detail. MIRI is the only Webb instrument sensitive to the mid-infrared region of the electromagnetic spectrum.

IC 5332 is located 29 million light-years from Earth. The galaxy has a diameter of roughly 66 000 light-years, making it about a third smaller than the Milky Way. It stands out for being nearly face-on to Earth, allowing us to marvel at the beautiful sweep of its spiral arms.

Webb Reveals IC 5332
This image of the spiral galaxy IC 5332, taken by the NASA/ESA/CSA James Webb Space Telescope with its MIRI instrument, has been scaled and cropped to match the NASA/ESA Hubble Space Telescope’s view of the same galaxy. Credit: ESA/Webb, NASA & CSA, J. Lee and the PHANGS-JWST and PHANGS-HST Teams

One of MIRI’s most remarkable features is that it operates 33 °C below the rest of the observatory at the frosty temperature of –266 °C. That means that MIRI operates in an environment only seven °C warmer than absolute zero, which is the lowest possible temperature according to the laws of thermodynamics.

A stunning image of the same galaxy captured in ultraviolet and visible light using data from Hubble‘s Wide Field Camera 3 is shown next to this extravagantly detailed mid-infrared image (WFC3). Some distinctions stand up right away.

Some differences are immediately obvious. The Hubble image shows dark regions that separate the spiral arms, whereas the Webb image shows a continual tangle of structures that echo the spiral arms’ shape. This difference is due to the presence of dusty regions in the galaxy.

Ultraviolet and visible light are far more prone to being scattered by interstellar dust than infrared light. Therefore dusty regions can be identified easily in the Hubble image as the darker regions that much of the galaxy’s ultraviolet and visible light has been unable to travel through.

NASA officially noted“Those same dusty regions are no longer dark in the Webb image, however, as the mid-infrared light from the galaxy has been able to pass through them. Different stars are visible in the two images, which can be explained because certain stars shine brighter in the ultraviolet, visible, and infrared regimes, respectively. The images complement one another in a remarkable way, each telling us more about IC 5332’s structure and composition.”


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