Webb delivers deepest image of Universe yet

The NASA/ESA/CSA James Webb Space Telescope has delivered the deepest, sharpest infrared image of the distant Universe so far.

Webb's image is approximately the size of a grain of sand held at arm's length - and reveals thousands of galaxies in a tiny sliver of vast Universe. This sharp near-infrared view has brought out faint structures in extremely distant galaxies, for an unprecedented look at galaxies billions of years in the past. For the first time, Webb has also detailed chemical makeup of galaxies in very early Universe.

Known as Webb's First Deep Field, this is galaxy cluster SMACS 0723 and it is teeming with thousands of galaxies - including the smallest, faintest objects ever observed. Webb's image is approximately the size of a grain of sand held at arm's length, a tiny sliver of the vast universe.

The combined mass of this galaxy cluster acts as a gravitational lens, magnifying more distant galaxies, including some seen when the universe was less than a billion years old. This deep field, taken by Webb's Near-Infrared Camera (NIRCam), is a composite made from images at different wavelengths, totaling 12.5 hours - achieving depths at infrared wavelengths beyond the Hubble Space Telescope's deepest fields, which took weeks. And this is only the beginning. Researchers will continue to use Webb to take longer exposures, revealing more of our vast Universe.

This image shows the galaxy cluster SMACS 0723 as it appeared 4.6 billion years ago, with many more galaxies in front of and behind the cluster. Much more about this cluster will be revealed as researchers begin digging into Webb's data. This field was also imaged by Webb's Mid-Infrared Instrument (MIRI), which observes mid-infrared light.

Webb's NIRCam has brought distant galaxies into sharp focus - they have tiny, faint structures that have never been seen before, including star clusters and diffuse features.

Light from these galaxies took billions of years to reach us. We are looking back in time to within a billion years after the big bang when viewing the youngest galaxies in this field. The light was stretched by the expansion of the Universe to infrared wavelengths that Webb was designed to observe. Researchers will soon begin to learn more about the galaxies' masses, ages, histories, and compositions.

Other features include the prominent arcs in this field. The powerful gravitational field of a galaxy cluster can bend the light rays from more distant galaxies behind it, just as a magnifying glass bends and warps images. Stars are also captured with prominent diffraction spikes, as they appear brighter at shorter wavelengths.

Webb's MIRI image offers a kaleidoscope of colours and highlights where the dust is - a major ingredient for star formation, and ultimately life itself. Blue galaxies contain stars, but very little dust. The red objects in this field are enshrouded in thick layers of dust. Green galaxies are populated with hydrocarbons and other chemical compounds.

Researchers will be able to use data like these to understand how galaxies form, grow, and merge with each other, and in some cases why they stop forming stars altogether.

In addition to taking images, two of Webb's instruments also obtained spectra - data that reveal objects' physical and chemical properties that will help researchers identify many more details about distant galaxies in this field. Webb's Near Infrared Spectrograph (NIRSpec) microshutter array observed 48 individual galaxies at the same time - a new technology used for the first time in space - returning a full suite of details about each. The data revealed light from one galaxy that travelled for 13.1 billion years before Webb's mirrors captured it. NIRSpec data also demonstrate how detailed galaxy spectra will be with Webb observations.

Finally, Webb's Near-Infrared Imager and Slitless Spectrograph (NIRISS) used Wide-Field Slitless Spectroscopy to capture spectra of all the objects in the entire field of view at once. Among the results, it proves that one of the galaxies has a mirror image.

SMACS 0723 can be viewed near the constellation Volans in the southern sky.

Webb's first deep field using MIRI and NIRCam
Paris (ESA) Jul 14 - Galaxy cluster SMACS 0723 is a technicolour landscape when viewed in mid-infrared light by the NASA/ESA/CSA James Webb Space Telescope. Compared to Webb's near-infrared image at right, the galaxies and stars are awash in new colours.

Start by comparing the largest bright blue star. At right, it has very long diffraction spikes, but in mid-infrared at left, its smaller points appear more like a snowflake's. Find more stars by looking for these telltale - if tiny - spikes. Stars also appear yellow, sometimes with green diffraction spikes.

If an object is blue and lacks spikes, it's a galaxy. These galaxies contain stars, but very little dust. This means that their stars are older - there is less gas and dust available to condense to form new stars. It also means their stars are aging.

The red objects in this field are enshrouded in thick layers of dust, and may very well be distant galaxies. Some may be stars, but research is needed to fully identify each object in the mid-infrared image.

The prominent arcs at the centre of the galaxy cluster, which are galaxies that are stretched and magnified by gravitational lensing, appear blue in the Mid-Infrared Instrument (MIRI) image at left and orange in the Near-Infrared Camera (NIRCam) image at right. These galaxies are older and have much less dust.

Galaxies' sizes in both images offer clues as to how distant they may be - the smaller the object, the more distant it is. In mid-infrared light, galaxies that are closer appear whiter.

Among this kaleidoscope of colours in the MIRI image, green is the most tantalizing. Green indicates a galaxy's dust includes a mix of hydrocarbons and other chemical compounds.

The differences in Webb's images are owed to the technical capabilities of the MIRI and NIRCam instruments. MIRI captures mid-infrared light, which highlights where the dust is. Dust is a major ingredient for star formation. Stars are brighter at shorter wavelengths, which is why they appear with prominent diffraction spikes in the NIRCam image.

With Webb's mid-infrared data, researchers will soon be able to add much more precise calculations of dust quantities in stars and galaxies to their models, and begin to more clearly understand how galaxies at any distance form and change over time.

NIRCam was built by a team at the University of Arizona and Lockheed Martin's Advanced Technology Center.

MIRI was contributed by ESA and NASA, with the instrument designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.

Related Links
Webb at ESA
Stellar Chemistry, The Universe And All Within It

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NASA releases first full set of images from $10B James Webb Space Telescope
Washington DC (UPI) Jul 12, 2021
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