Webb Space Telescope images reveal complex structures in a spiral galaxy

It used the mid-infraRed instrument, which works near absolute zero temperature.
Ameya Paleja
IC5332 as captured by the Webb Space Telescope
IC5332 as captured by the Webb Space Telescope

European Space Agency 

In yet another feat, the $10-billion James Webb Space Telescope has peered through the cosmic dust and brought pictures of complex structures inside a spiral galaxy 29 million light years away from us. The images released by the European Space Agency this week reiterate the telescope's capabilities.

The image shown above is of the spiral galaxy IC5332, which is almost perfectly face-on with respect to the Earth, providing a broad view of the extensive sweep of its spiral arms. With a diameter estimated to be roughly 66,000 light years, the IC5332 is approximately a third of the size of our galaxy, the Milky Way.

The James Webb Space Telescope (JWST) used its Mid-InfraRed Instrument (MIRI) to capture the image.

What do we know about MIRI on the JWST?

The MIRI is the only instrument on the space telescope that can capture light in the range of 5-28 micrometer wavelength, while all the others work in the near-infrared spectrum. To do so, the instrument relies on specialized detectors that are kept at temperatures of -446oFahrenheit (-266oC), which is extremely close to the absolute zero that the laws of thermodynamics state we can reach.

This is not a significant achievement on the JWST since the rest of the instruments operate at temperatures 33oC higher than this. Nevertheless, the MIRI has a dedicated cooling system to ensure its detectors are maintained at the correct temperatures.

The ESA highlighted that capturing images in the mid-infrared wavelength was challenging on Earth since the atmosphere absorbs the wavelength while the heat emanating from the planet also complicates measurements.

Comparison with Hubble's images

Like other images taken by the JWST, the image of the spiral galaxy too is being compared to that captured by its predecessor, the Hubble Space Telescope. Last month, Interesting Engineering reported images of yet another spiral galaxy, the M74 Phantom, which were also shared by the ESA.

It is important to note that Hubble's images look strikingly different from those of the JWST since the former was not equipped with sophisticated cooling systems for its mirrors and did not capture any images in the mid-infrared wavelength. So, the Webb Space Telescope can see what the Hubble could not.

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The Hubble captured images using its visible light and ultraviolet sensors on its Wide Field Camera 3 (WFC3). While the JWST image has dark hollow regions, Hubble's images are complete and continuous. The ESA attributes this to the dusty regions in the galaxy that scatter visible and ultraviolet light and appear as dark regions in the Hubble image. In comparison, infrared light passes through this region and has been captured in Webb images.

There is also a difference in the stars visible in the two images. Since different stars shine differently, and while some may have been visible in Hubble's ultraviolet and visible spectrum images, others can be spotted in JWST's mid-infrared images. The superimposition of these images isn't just a comparison to determine how much better JWST is but also to complement the data that scientists already have thanks to the Hubble.

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