James Webb Space Telescope: Image comparison reveals its true power versus Hubble

A section of sky the size of a grain of sand expanded into a mosaic of ancient stars.
Chris Young
Hubble's image (left) and the one taken by James Webb (right).1, 2

James Webb's scientific journey has finally begun.

Yesterday, July 11, President Biden and NASA Administrator Bill Nelson revealed the first full-color image taken by the James Webb Space Telescope (JWST). NASA described it as the "deepest, sharpest infrared view of the universe to date."

There is a mind-blowing amount of data to marvel at in the first scientific James Webb image — the patch of sky is roughly the size of a grain of sand when viewed from Earth, but it contains thousands of galaxies, each of which likely contains billions of stars and planets.

And that wasn't all. NASA has just revealed a stunning set of four more observations made by JWST. To highlight James Webb's immense technical prowess, we can look at the same regions of the sky as viewed by its predecessor, the Hubble Space Telescope

Side-by-side images highlight the power of James Webb

The image shared yesterday by NASA provides a stunning view of galaxy cluster SMACS 0723 in never-before-seen detail. The light from those systems took so long to reach James Webb's instruments that it essentially provides a window into the universe some 4.5 billion years ago.

It's not the first time one of NASA's key instruments was pointed at this section of the sky. Images taken of SMACS 0723 by the Hubble Space Telescope are available at the RELICS Treasury Program. It's worth noting that the image taken by Hubble required 10 days of exposure, while the JWST's Near-Infrared Camera image took only 12.5 hours to take the image revealed yesterday.

A Google and Fitbit UX designer, Jason Short, put together a GIF for a quick side-by-side impression of James Webb's image and the one taken by Hubble. The comparison highlights just how much clearer and brighter JWST's image is — meaning it essentially peers much further into the universe and into the past.

NASA has pointed out that the spikes coming off bright objects in the JWST image of SMACS 0723 are not lens flares. They occur when light from bright objects such as stars is bent by the edges of the telescope. They are less prominent in mid-infrared.

The image above, shared by The Australian, shows the entire James Webb image compared to the same section of the sky captured by Hubble.

NASA shares a wealth of new James Webb images

Today, NASA revealed new images taken by James Webb alongside earlier observations taken by Hubble of the same cosmic targets. The image of Stephan's Quintet (below) shows a visual grouping of five galaxies. NASA referred to them as "dancing galaxies", and now we can see them in more detail than ever before.  

Fun fact: An image of Stephan's Quintet was used in the classic movie "It's a Wonderful Life".

James Webb Space Telescope: Image comparison reveals its true power versus Hubble
The JWST image of Stephan's Quintet (left) and one taken by Hubble in 2009 (right). Source: NASA/Twitter

The Southern Ring, or "Eight-Burst" nebula, seen below has a dying star at its center. It is located approximately 2,000 lightyears away from Earth. Hubble captured an impressive image in 1998.

Now, with James Webb's Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI) cameras, we can see the nebula with stunning new clarity and learn more about the final moments of massive stars.

James Webb Space Telescope: Image comparison reveals its true power versus Hubble
The JWST image (left) and the Hubble image (right) of the Southern Ring. Source: NASA/Twitter

NASA saved its most stunning new James Webb image for last, and it is the one that marks a most striking departure from earlier observations by Hubble. The image shows the star-forming region NGC 3324 behind the Carina nebula, located some 7,600 lightyears away.

James Webb Space Telescope: Image comparison reveals its true power versus Hubble
The JWST image of Carina nebula (top) and a Hubble composite (bottom). Source: NASA/Twitter

The mesmerizing image shows off the JWST Near Infrared Camera's capacity to peer through dust clouds and observe baby stars forming in one of the universe's many stellar nurseries. By contrast, Hubble's image was only able to collect a fraction of the starlight. James Webb will shed new light on the early universe and also on stars in their very earliest evolutionary phase.

The Hubble Space Telescope's first scientific image

We already have an impressive number of side-by-side images to compare Hubble and James Webb by so early in the latter's operational timeline. But another striking way to compare the two observatories is to look at Hubble's very first scientific image.

Hubble's first image (below) compared even to later observations made by the now-32-year-old telescope reveals a striking contrast.

James Webb Space Telescope: Image comparison reveals its true power versus Hubble
Hubble's first observation alongside a ground-based picture from Las Campanas, Chile, Observatory of the same region of the sky. Source: NASA, ESA, STScl

The relatively low-detail image shows how the iconic Hubble needed time to get its bearings before revealing its most impressive observations to the world. The same may be the case for James Webb — despite the incredible detail in that image of SMACS 0723  — meaning we've only scratched the surface of what is to come.

James Webb versus Hubble

The main reason James Webb has so much more power than Hubble is due largely to its massive 21-feet (6.5-meter) diameter gold-coated mirror. Hubble's mirror, by comparison, is a much smaller 7.8 feet (2.4 meters) in diameter.

Crucially, given its mission goals, James Webb also has more capacity for capturing distant stars in the infrared spectrum. As NASA points out, "the instruments on Hubble can observe a small portion of the infrared spectrum from 0.8 to 2.5 microns, but its primary capabilities are in the ultra-violet and visible parts of the spectrum from 0.1 to 0.8 microns." 


Infrared observations are particularly valuable when it comes to observing the earliest stars and galaxies in the universe, as many of these are hidden behind clouds of dust that absorb visible light. Infrared light is able to pierce these dust clouds, meaning James Webb can capture starlight from behind massive "cosmic cliffs" like the Carina nebula.

All of this makes us incredibly excited to see what else NASA and James Webb have in store. Stay posted for more from James Webb.

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