Keren Sharon, associate professor of astronomy: The first JWST images are all stunning, but their beauty goes deeper than “just” being aesthetically pleasing. In the image of SMACS 0723, the galaxy cluster is a strong gravitational lens—it is so massive that it bends space-time and adds cosmic magnification to our observations. The superb capabilities of JWST, in terms of wavelength and sensitivity, combined with the magnification from gravitational lensing, let us see farther into the Universe, and deeper into the past, than ever before. Its resolution allows us to see very small internal structures within faraway galaxies, really breaking them down to their building blocks. We will learn so much about how galaxies form their stars over cosmic time from these data. 

David Gerdes, Arthur F. Thurnau Professor and chair of physics: The breathtaking images also show how the JWST will continue to reveal previously inaccessible secrets of our universe. This discovery potential is possible because of JWST’s two “superpowers”: its large mirror and its ability to see infrared light. JWST’s mirror has over six times the light-gathering area of the Hubble Space Telescope, which means it can detect much fainter objects than we could before.

By seeing infrared light, the JWST can peer inside the dusty regions of our galaxy, where new stars and worlds are being born, and observe some of the universe’s earliest galaxies, whose light went out nearly 13 billion years ago. JWST’s powerful spectrograph can break infrared light into its component colors, revealing the chemical compositions of galaxies, stars, and planets.

KS: SMACS 0723 is an image of a cluster of galaxies: clusters of galaxies are some of the most massive objects in the universe, weighing about 1015 the mass of Earth’s sun. They are mostly made of dark matter, which we can’t see. The hundreds of galaxies and hot gas in the cluster show us where these clusters are.

These structures are so massive that they bend space-time itself, a phenomenon that was predicted by Einstein’s general relativity. Because of this curved space-time, the path of light that is coming towards us from a background source, is bent. Like an optical lens or a human-made telescope, the gravitational lens focuses the light rays and the object we’re looking at appears magnified. This optical illusion can even create multiple images of the same background galaxy.

In this JWST image it is very obvious—just look at some of those yellowish curved galaxies and notice how they look almost identical to each other! They are quite strikingly mirror images. The magnification lets us see these galaxies in really high resolution. For example, look at the little round speckles that appear to swarm some of the galaxies—these are likely individual star clusters, or star forming regions, which are usually too small for us to see at such high distances.


A detail from JWST’s first deep field, strong lensing galaxy cluster SMACS 0723. Two mirror images of the same background galaxy appear here; the superb resolution reveals details of their internal structure and star formation.


DG: Other images show a star-forming nebula of dust and gas, a beautiful quintet of galaxies, and rings of gas thrown off by a dying star. As a solar system astronomer, I’d like to highlight an image that may be the least visually stunning, but possibly the most tantalizing. The JWST’s near-infrared spectrograph measured the spectrum of the exoplanet known as WASP 96-b, a gas giant similar to Jupiter that orbits its star every three and a half days.

The spectrum shows unmistakable chemical signatures of water vapor in the planet’s atmosphere, as well as evidence for clouds or haze. The discovery of water vapor in exoplanetary atmospheres isn’t new—Hubble has made such measurements before—but the speed with which JWST obtained this result means that JWST will represent a quantum leap forward in our ability to search for habitable worlds. 

DG: The JWST is a technological tour de force, which accounts for the stunning detail of these images and also helps explain the many delays in launching it into space. Compared to Hubble, which has a single 2.4-meter mirror, the heart of the JWST is a 6.5-meter light-gathering mirror that consists of 18 hexagonal segments. While Hubble circles the Earth in a relatively low orbit, allowing it to be serviced by the space shuttle, the JWST actually orbits the sun at a special location known as Earth’s second Lagrange point, or L2. It’s about four times farther from the Earth than the moon, and cannot be visited by astronauts. The JWST has a giant shade to shield the telescope from the sun’s heat and light, providing for ultra-stable observing conditions. Both the shade and the segmented mirror needed to be carefully unfurled and deployed once the telescope was in space. It was a heart-stopping series of maneuvers, and they were executed to perfection.

KS: The images from JWST were publicly available almost immediately after they were first shown to the world. This means that anyone—anyone!—can download and explore them. This has been the mode of operation for the Hubble Space Telescope as well: the data belong to everyone.

My undergraduate and graduate students are so excited to be able to have their hands on such exquisite data. This week they were all “elbow deep” in these images, looking for evidence of gravitational lensing, comparing and contrasting the new data with data we previously had from Hubble. 

DG: These images, and the many that will follow over the JWST’s 20-year lifetime, will redefine astronomy in the 21st century. Their beauty will certainly inspire the next generation of astrophysicists and astronomers. But beyond that, I hope they will cause every human being to pause and reflect on the fact that we inhabit a single, fragile speck in a vast and beautiful universe. 

KS: JWST is better, in every aspect, than anything we’ve dreamed it would be. I am in awe of this technological achievement, and thankful to the hundreds of people who worked tirelessly to make it happen. Yes, the images alone are beautiful, but learning from such pretty pictures about how the universe works and what it’s made of makes them truly breathtaking. 



Image credit: NASA ESA CSA STScI