Evrim Yazgin
Cosmos science journalist
Late last month, NASA’s James Webb Space Telescope completed its seventh and final alignment phase. Now, all four of its instruments are in full focus and engineers have begun compiling test images. A test image showing the observatory’s full field of view is now being more closely examined and it reveals the power of the new telescope.
The focus is on the image taken by Webb’s coldest instrument, the Mid-Infrared Instrument (MIRI).
MIRI’s operating temperature is 7 kelvin, or -266°C – only 7 degrees Celsius above absolute zero. It is cooled by an innovative “cryocooler“. MIRI and the other instruments on Webb must be cooled because they are trying to pick up infrared radiation, which is experienced by humans every day as heat. The telescope has to be cooled so the instrument’s own generated heat doesn’t distort the images taken.
MIRI photographed the Large Magellanic Cloud taking in infrared radiation with a wavelength of 7.7 micrometres. The Large Magellanic Cloud is a small satellite galaxy of the Milky Way about 160,000 lightyears from Earth. The cloud provides a dense star field which is perfect for testing MIRI’s performance.
NASA has compared the image taken by MIRI with a picture of the same target taken by NASA’s now retired Spitzer Space Telescope’s Infrared Array Camera. Spitzer’s image was taken at 8.0 microns. Webb’s significantly larger primary mirror and improved detectors gives us infrared images of far-improved clarity, enabling future discoveries.
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Webb’s MIRI image shows interstellar gas in astonishing detail. Emissions from polycyclic aromatic hydrocarbons – molecules of carbon and hydrogen important to the thermal balance and chemistry of interstellar gas – are seen.
Studying systems such as these, MIRI will provide new insights into the formation of stars and protoplanetary systems that lead to structures like our own Solar System.
The full field view images were met with delight by scientists involved in Webb’s development.
“These remarkable test images from a successfully aligned telescope demonstrate what people across countries and continents can achieve when there is a bold scientific vision to explore the universe,” says Lee Feinberg, Webb optical telescope element manager at NASA’s Goddard Space Flight Center.
Scott Acton, Webb wavefront sensing and controls scientist at Ball Aerospace, adds: “These images have profoundly changed the way I see the universe. We are surrounded by a symphony of creation; there are galaxies everywhere! It is my hope that everyone in the world can see them.” After testing and setting up, Webb will begin scientific observations this northern summer.