On July 12, NASA shared the first images of the fully operational James Webb Space Telescope (JWST) – the most powerful space observatory ever built.
Among the close-ups of cosmic cliffs and stellar fireworks was an incredibly detailed image known as Webb’s first deep field. The image is full of shimmering stars, distorted light trails, and thousands upon thousands of gem-like galaxies sparkling against the darkness of space deepest picture of the universe ever done.
It’s, to put it simply, a lot to digest.
“You start looking at this picture and you realize there’s no such thing as an empty sky,” Scott Gaudi, a professor of astronomy at Ohio State University, told Live Science. “Something crazy is happening everywhere.”
To try to understand this historical picture a little better, we asked Gaudi to walk us through the big, small, and weird details of Webb’s Tiefenfeld.
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The brightest bunch
Let’s start with the galactic elephant in the room: the Colossal galaxy Cluster in center of image.
The focal point of Webb’s deep-field image is a large, bright galaxy cluster called SMACS 0723, located about 4.6 billion light-years away Earth – which means that the light we see here was emitted just before our planet formed. You can see the cluster as a series of bright points of light in the center of the image, surrounded by a smeared white halo of more diffuse starlight.
Galaxy clusters are some of the largest gravitationally bound structures in the Universe, containing hundreds to thousands of individual galaxies all clustered together. The brightest points of light in the center of the image represent some of these larger galaxies – several of which appear to be actively merging, Gaudi said.
When galaxies collide, it literally creates a hot mess. Huge clouds of star-forming gas collapse, compress, and heat up, forming myriad new stars that “spit out,” Gaudi said, from the colliding galaxies.
These spat out stars — likely numbering in the millions or even billions and not gravitationally bound to any of the galaxies within the cluster — produce a veil of white known as intra-cluster light.
JWST shows us this light in more detail than ever before, adding evidence to a long-held theory that galaxy clusters store a good chunk of their mass in these regions within the cluster, Gaudi said.
A cosmic magnifying glass
Mass is exactly what makes SMACS 0723 such a good target; This cluster of galaxies is so massive that it distorts the light from stars and galaxies billions of light-years behind it (relative to our view from Earth). This leads to the next key feature of the JWST deep-field image – gravitational lensing.
“The next thing that probably catches your eye are these weird, worm-shaped arches that sort of emanate from the center of the picture,” Gaudi said. “These are background galaxies that sit behind the foreground cluster. As its light hits the cluster, the cluster mass bends that light and creates what is called a gravitational lens.”
Related: The James Webb Space Telescope will study the Milky Way’s flickering supermassive black hole
Like the cosmic combination of a magnifying glass and a funhouse mirror, gravitational lenses distort and magnify light from background galaxies. If you think of the center of this image as a clock, you can clearly see two such background galaxies sitting between 2 and 3 o’clock and 7 and 9 o’clock, respectively.
Both galaxies appear as bright, orange, curving lines that curl around the central cluster of galaxies. They appear incredibly long – longer even than the massive central cluster – because their light is amplified so dramatically. Despite their large and ominous appearance, the galaxies are actually more than 13 billion light-years away, Gaudi said — potentially making them the oldest observable galaxies in the universe.
But the mass of the central cluster doesn’t just add to these ancient objects—it doubles them. Look a little closer and you’ll see that the two distorted orange lines are lighter at the edges and darker in the middle. Look even closer at one of the orange lines and you’ll see that the two bright areas are actually perfect mirror images of each other.
According to Gaudí, this is a telltale by-product of gravitational lensing — a galaxy split into multiple images that curve around the same center of mass. Gaudí added that almost every distorted-looking object on display here has a reflection somewhere else in the field.
Studying the oldest light in the universe is one of NASA’s main goals for the JWST. But as this image shows, the powerful telescope can’t peer into the past without thousands upon thousands of younger, closer galaxies bombarding the image.
In general, the large, bright, six-pointed objects in the foreground of the image are stars. Almost everything else you can see is a galaxy or galaxy cluster, Gaudi said.
These galaxies come in two main varieties. Look to the right of the bright star in the center of the image and you’ll see a perfect spiral galaxy, just like our own Milky Way. Spiral galaxies are active, star-forming galaxies, Gaudi said, and they tend to be filled with hotter, younger stars that glow with whitish-bluish light.
Look slightly above and to the left of this spiral and you’ll see the other dominant galaxy type in our local universe: a fiery orange elliptical galaxy.
“Elliptical galaxies are kind of dead,” said Gaudi. “They have already formed all their stars. The massive blue stars die first, and the old red stars remain.”
In general, the blue galaxies in this image are younger spiral galaxies, while the redder galaxies are old, dead elliptical galaxies.
However, a galaxy’s color can also be changed by its distance from the telescope, thanks to a phenomenon called redshift. Basically when the light travels the expanse expanding universe, its wavelength gradually increases with distance and becomes redder with time. So some of the red and orange galaxies in this image are actually old background galaxies whose light has been redshifted en route to the JWST lens.
Estimating the age of the thousands of objects found in this image is just one of the exciting challenges scientists await. And the longer the researchers look into the deep field, the more strange and wonderful things they will discover.
For example, Gaudi pointed to an orange N-shaped galaxy zigzagging to the right of the perfect spiral galaxy, seemingly distorted and twisted by an intense cosmic collision. Gaudí dubbed this the “Fusion Train Wreckage Galaxy” because of its chaotic and jumbled appearance.
With the first images only days old and more than 20 years of fuel awaiting aboard the JWST, the discoveries have only just begun. We hope you enjoy getting lost in space.
Originally published on Live Science.