The universe is cold and dark. And yet, within the dark, there is a faint glow of warmth. Across the sky, there are objects that emit infrared light, similar to the light that warms your hands near a campfire. By observing this light, astronomers can see the cosmos in a way that looks very different from that seen by our eyes.
Both ground-based and space-based infrared telescopes have been around for quite some time, but with the launch of the James Webb Space Telescope (JWST), astronomers will be able to capture the infrared sky in unprecedented detail. It will allow us to see warm planets huddled near their star, and distant galaxies so ancient that their bright visible light has redshifted to faint infrared. It will change our understanding of the early universe and perhaps reveal evidence of alien life.
But there is one aspect of the JWST that is very limiting. It is designed to capture high-resolution images of small areas of the sky. This is true for most telescopes since it is difficult to create an image with is both wide and detailed. Because of this, JWST will only be able to capture a fraction of the sky over time. For example, the Hubble Space Telescope has given us amazing views of the heavens, but in its 30-year mission, it has only captured about 0.1% of the visible sky.
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To counter this limitation we can create sky-survey telescopes. The Vera Rubin Observatory is being constructed specifically for this purpose. Its 8-meter mirror is designed to give a view of the sky several Moon-widths across. When completed, it will capture most of the southern sky every few days. It will not only allow astronomers to study a vast range of celestial objects, but it will also allow them to study how these objects change over time. It will be an amazing tool for visible light astronomy, but what about infrared?
This is where the upcoming SPHEREx mission comes in. Scheduled to launch by April of 2025, SPHEREx will capture 99% of the sky every six months. This does come at a cost of resolution. The SPHEREx images will not be nearly as detailed as JWST. But since they will both observe infrared light they can work together to see more of our universe. SPHEREx will focus on the background heat of the deep universe, and look for water and complex organic molecules hidden within the gas and dust of stellar nurseries. And when SPHEREx finds something unusual, JWST can step in for a closer look.
The James Webb Telescope will surely give us some amazing views over the next few years. With SPHEREx coming soon on its heels, the infrared revelations of JWST are surely just the beginning.
Reference: The SPHEREx Mission