James Webb Space Telescope versus Hubble: how the images of these telescopes compare

The first full-color images from NASA’s James Webb Space Telescope were released this week, rocking the world of anyone who has been waiting decades for this major upgrade in space-based photography.

The James Webb Space Telescope, or JWST, is the new heavyweight in the world of space telescopes. It has the biggest mirror, the newest tech, and is playing on hard mode — nearly a million miles away from Earth. It’s been hailed as the future of astronomy and astrophysics, capable of peering into the most distant reaches of the Universe. But it’s still a rookie. For the past three decades, the superstar of the skies has been Hubble, a NASA telescope launched in 1990 that has taken absolutely epic images of planets, stars, galaxies, nebulae, and so many other astronomical wonders.

Since it was based in low Earth orbit, Hubble could take detailed images of the cosmos without Earth’s pesky atmosphere getting in the way, and the pictures that it took were astounding. In the past 32 years, it has made 1.5 million observations and spawned more than 19,000 scientific papers, according to NASA.

That’s a whole lot of science. Now, JWST is set to take the baton from Hubble, pushing our understanding of the Universe even further. NASA calls JWST “the scientific successor to Hubble” in a blog post comparing the two observatories. Without Hubble’s observations of the Universe, researchers wouldn’t have prioritized building a telescope that could peer into the places that even Hubble couldn’t. Here’s a closer look at how images from the two titans of the sky stack up.

Deep field

This is Hubble’s first deep field photo, taken in 1995 and released in 1996. It was the deepest image of the Universe ever taken. To get this picture, researchers took 342 images over 10 days with a total exposure of 100 hours. It revealed over 3,000 galaxies scattered across a tiny patch of sky.

Hubble’s operators got even better at taking these kinds of photos over the next few decades and kept looking deeper into space.

Image: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University), and the HUDF09 Team

This is the Hubble eXtreme Deep Field image, released in 2012. There are more than 5,500 galaxies visible in this image. Over the course of a decade, researchers gathered 50 days’ worth of observations of one concentrated area, resulting in an exposure of 2 million seconds (more than 23 days).

Then came JWST.

Image: NASA, ESA, CSA, STScI, Webb ERO

JWST’s first full-color scientific image was revealed by President Joe Biden on July 11th as a teaser of what was to come. While Hubble’s deep fields took days (if not weeks) of exposure, JWST was able to capture this image after just 12.5 hours.

To put this in perspective, it shows part of the sky “approximately the size of a grain of sand held at arm’s length by someone on the ground,” as NASA put it. In that patch of sky is a galaxy cluster, SMACS 0723, 4.6 billion light-years away. It’s so massive that it bends space-time, leaving us with a cosmic magnifying glass, bringing faint galaxies even farther away into focus. Some of these are the faintest infrared objects ever seen in science, and scientists can’t wait to learn more about them.

Bonus: Images of SMACS 0723 were obtained by RELICS, a scientific survey. RELICS used images from Hubble and another space telescope, Spitzer, to look for galaxies with similar properties to SMACS 0723. You can see those early images here.

Carina Nebula

Image: NASA, ESA, and The Hubble Heritage Team (STScI/AURA); acknowledgment: N. Smith (University of California, Berkeley)

This is one of Hubble’s favorite subjects, the Carina Nebula, 7,200 light-years away. This particular image was released by the Hubble Heritage Project in 2008 and shows a sliver of a star-forming region in a corner of the nebula.

It looks like an impressionist landscape, with hills, valleys, and towers made of gas and dust strewn across the image, with only a hint of the bright stars behind the nebula peeking through. It’s a gorgeous vista, and JWST’s updated image provides the same awe but in a much sharper picture.

Image: NASA, ESA, CSA, STScI

Much sharper. There are stars here that used to be completely hidden by gas and dust. This image is so stunning it even left the scientist presenting it at the big press conference at a loss for where to start. “Honestly, it took me a while to even figure out what to call out in this image. There’s just so much going on here. It’s so beautiful,” Amber Straughn, deputy project scientist for JWST at NASA, said.

Stephan’s Quintet

Image: NASA, ESA, and the Hubble SM4 ERO

This group of five galaxies is stunning in this Hubble picture from 2009, after the space telescope got a camera upgrade earlier that year. The 2009 mission sent the Space Shuttle to visit Hubble for a fifth and final time and gave the observatory a major tune-up. In addition to the new camera that took this picture, the telescope got upgraded and repaired. The ability for astronauts to visit the Hubble in low Earth orbit kept it in action for a very long time.

JWST will not have that advantage — situated nearly a million miles away, it’s too far away for the regular checkups that Hubble got. But it does have about 20 years’ worth of fuel onboard, which means we will get many more images like this:

Image: NASA, ESA, CSA, STScI

That’s one of JWST’s views of the group of galaxies, which were first observed in 1877 (and had a star turn in It’s a Wonderful Life). The one in the upper left is a bit of the outsider in the group — it’s much closer to Earth than the other four, which actually are very close together. They’re so close together that JWST can see shock waves from interactions between these galaxies as they tug at each other.

The image above is the biggest image JWST has taken yet, and it’s a mosaic made with over 1,000 individual pictures taken by two instruments: the Near Infrared Camera (NIRCam) and the Mid-Infrared Instrument (MIRI). Both gather infrared wavelengths of light, which help JWST see through gas and dust. But, as the names imply, they both gather slightly different wavelengths of that infrared light. Combined, they create a gorgeous image, but taking a closer look at the views from just one of the instruments can be revealing, too.

Image: NASA, ESA, CSA, STScI

This is Stephan’s Quintet as seen by MIRI. This composite image gives another perspective on the galaxy group and provides researchers with extraordinary new details to wonder over.

Each of the colors in this image has a different significance, as the Space Telescope Science Institute, which operates JWST, explains:

In this image, red denotes dusty, star-forming regions, as well as extremely distant, early galaxies and galaxies enshrouded in thick dust. Blue point sources show stars or star clusters without dust. Diffuse areas of blue indicate dust that has a significant amount of large hydrocarbon molecules. For small background galaxies scattered throughout the image, the green and yellow colors represent more distant, earlier galaxies that are rich in these hydrocarbons as well.

Oh, and that super bright point at the center of the top-most galaxy? Yeah, that’s an active supermassive black hole. While we can’t see the black hole itself, we can see the light from all the material that’s getting pulled into it — and it’s shining as bright as 40 billion suns.

Southern Ring Nebula

Image: STScI/AURA/NASA/ESA

Last but certainly not least is the Southern Ring Nebula. Here it is, imaged by Hubble in 1998. The “ring” is the detritus of a dying star — the dimmer of the two bright spots at the center of the image. Now a small white dwarf, the star that caused all this commotion was a star about the size of our Sun. It ran out of fuel and threw off its outer layers of gas, creating the ring you see here. The ring is about half a light-year across, and the gases are moving outward at a speed of about 9 miles per second.

Image: NASA, ESA, CSA, and STScI

Here’s the Southern Ring Nebula as seen by two of JWST’s instruments, NIRCam and MIRI. On the left is the nebula as imaged by NIRCam, in near-infrared light. MIRI’s version — in mid-infrared — is to the left.

There’s a lot of differences between the two images, but one fascinating tidbit is the stars, which look decidedly more spiky on the left. That’s because the two instruments are gathering different wavelengths of light. “In near-infrared light, stars have more prominent diffraction spikes because they are so bright at these wavelengths. In mid-infrared light, diffraction spikes also appear around stars, but they are fainter and smaller (zoom in to spot them),” the Space Telescope Science Institute explains.

Near-infrared also provides much sharper images than mid-infrared because the wavelengths of light are so much shorter. But both offer an indescribably beautiful new look at the cosmos around us.