Now that all of JWST's science instruments have been aligned with the telescope's optics and are all operating at their (very cold) operating temperatures, we have seen some of the test images it has sent back. These images are very impressive but they become even more so when directly compared with our previous infrared observatory in space. Now, NASA has released two images of the same part of the sky taken by Spitzer and JWST to demonstrate just that.
JWST, now the largest and more powerful telescope ever sent to space, is the successor of Hubble (which still works very hard, thank you very much) and the Spitzer Space Telescope, which was retired a few years ago. Spitzer brought incredible new insights to our understanding of the universe by giving us an infrared eye into the cosmos and providing us with the first high-resolution images of the universe in near- and mid-infrared.
JWST will also peer into the cosmos in infrared, but with an eye that is much sharper, as you can see here. As NASA said, Spitzer walked so JWST could run.
In this comparison animated gif, we see Spitzer's and JWST's view of a part of the Large Magellanic Cloud, the largest companion galaxy that orbits our own, the Milky Way. Spitzer's Infrared Array Camera, which observes light with a wavelength of 8 microns, identifies the stars and the interstellar gas in the nearby galaxy.
But JWST's Mid-Infrared Instrument (MIRI), sees the same with unprecedented clarity. The emission of “polycyclic aromatic hydrocarbons,” important molecules in interstellar space, is seen clearly with all their strands and nebulosity. This is the difference between Spitzer's 0.85-meters (2.8 feet) primary mirror and JWST's whopping 6.5-meter (21 feet) one.
While the space telescope continues to be tested, NASA officials confirmed yesterday that the first scientific images are expected to be delivered in mid-July, though it's still hush hush what the target will be.