A young cluster of galaxies sparkles under a cosmic glow that’s 4.4 billion years old. This peek into the past shows the stellar spectacle of a galaxy cluster still forming.
What is it?
The James Webb Space Telescope snapped this image of the galaxy cluster MACS J0553.4-3342 on July 3 using its near-infrared camera (NIRCam). The glorious, glimmering sight is actually a massive young galaxy cluster forming 4.4 billion years ago. A galaxy cluster is a grouping of galaxies held together by gravity. Galaxy clusters can contain hundreds or even thousands of galaxies and are the largest known structures in the entire universe that are held together in this way.
Why is it incredible?
Because light takes time to travel through space, and because the JWST can look incredibly far out into space, this telescope acts as a sort time machine.
This power isn’t unique to the JWST, however. Other telescopes like the Hubble Space Telescope, for instance, have similarly peered back in time through the cosmos and revealed some incredible, ancient sights. However, the JWST’s specialized instruments like NIRCam allow the telescope to pick up incredibly faint light from galaxies remarkably far away. This greatly stretches how far back in time we can see.
But the really incredible thing is, you can look back in time yourself — with only your eyes. While JWST can look exceptionally far out into space and can capture the very faint light of ancient galaxies, the light coming from the stars you can see with your bare eyes also had to travel over incredible stretches of time to reach you. Think about this: the light coming from a constellation you love may have traveled across millions of light-years to get to your eyes.