On July 12, NASA shared the debut images from a fully operational James Webb Space Telescope (JWST) is the most powerful space observatory ever built.
Among the big plans space rocks and star fireworks was an incredibly detailed image, known as Webb’s first deep field. Filled with twinkling stars, twisted light trails, and thousands and thousands of gem-like galaxies twinkling against the darkness of space, the painting was advertised as the deepest image of the universe ever accepted.
This is, simply put, a lot to take in.
“You start looking at this image and realize that there is no empty sky in it,” Scott Gowdy, professor of astronomy at Ohio State University, told Live Science. “Something crazy is going on everywhere.”
To try and better understand this historical image, we asked Gaudí to show us the big, small, and weird details of Webb’s deep field.
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The brightest cluster
Let’s start with the galactic elephant in the room: the colossal galaxy cluster in the center of the image.
The focal point of Webb’s deep-field image is a large, bright cluster of galaxies known as SMACS 0723, about 4.6 billion light-years away. Earth – which means that the light we see here was emitted shortly before the formation of our planet. You can see this cluster as a series of bright spots of light in the center of the image, surrounded by a fuzzy white halo of more diffuse starlight.
Galaxy clusters are among the largest gravitationally bound structures in the universe, containing hundreds to thousands of individual galaxies clustered together. The brightest spots of light in the center of the image represent some of these large galaxies, some of which are actively merging, Gaudí said.
When galaxies collide, there is literally a hot mess. Huge clouds of star-forming gas collide, shrink and heat up to form countless new stars that are “spewing” from the colliding galaxies, Gaudí said.
These erupted stars, probably in the millions or even billions and not bound by gravity to any of the galaxies within the cluster, create a white haze known as light within the cluster.
The JWST shows us this light in clearer detail than ever before, Gaudí said, adding evidence to a long-standing theory that galaxy clusters store a significant portion of their mass in these regions within the cluster.
space magnifying glass
It’s the mass that makes the SMACS 0723 such a good target; this cluster of galaxies is so massive that it distorts the light of stars and galaxies billions of light-years away (compared to our view from Earth). This leads to the next key feature of JWST deep field imaging, gravitational lensing.
“Probably the next thing that catches your eye is the strange worm-shaped arcs coming from the center of the image,” Gaudí said. “These are the background galaxies that are behind the foreground cluster. Once their light hits the cluster, the mass of the cluster bends that light and creates what’s called a gravitational lens.”
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Like the cosmic combination of a magnifying glass and a curved mirror, gravitational lenses distort and magnify the light from background galaxies. If you visualize the center of this image as a clock, you can clearly see two such background galaxies located between 2 and 3 o’clock and 7 and 9 o’clock respectively.
Both of these galaxies appear as bright orange curved lines that wrap around the central cluster of galaxies. They appear incredibly long—longer even than the massive central cluster—because their light is magnified so much. Despite their large and looming appearance, the galaxies are actually more than 13 billion light-years away, potentially making them one of the oldest observable galaxies in the universe, according to Gaudí.
But the mass of the central cluster not only enlarges these ancient objects, but also doubles them. Look a little closer and you’ll see that both curved orange lines are brighter at the edges and dimmer in the center. 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.
It’s a clear by-product of gravitational lensing, Gaudí said – a single galaxy split into multiple images that curve around the same center of mass. Gaudí added that almost every deformed object on display here has a mirror image somewhere else.
Studying the oldest light source in the universe is one of NASA’s key goals for JWST. But as this image shows, a powerful telescope can’t peer into the past without thousands upon thousands of younger, nearby galaxies bombarding the frame.
In general, the large bright six-pointed objects in the foreground of the image are stars. According to Gaudí, almost everything else you can see is a galaxy or a cluster of galaxies.
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 ours. Milky Way. According to Gaudí, spiral galaxies are active star-forming galaxies, and they tend to be filled with hotter, younger stars that glow with a whitish-bluish light.
Look a little above and to the left of this spiral and you will see the other dominant type of galaxy in our local universe: the fiery orange elliptical galaxy.
“Elliptical galaxies are kind of dead,” Gaudí said. “They have already formed all their stars. The massive blue stars die first, and the old red stars remain.”
Typically, the bluer galaxies in this image are younger spiral galaxies, while the redder ones are older, dead elliptical galaxies.
However, the color of a galaxy can also change depending on its distance from the telescope, thanks to a phenomenon called redshift. In fact, as the light spreads over the vast and expanding universe, its wavelength gradually increases with distance, getting redder and redder over time. So some of the red and orange galaxies in this image are actually ancient background galaxies whose light has been redshifted on its way to the JWST lens.
Estimating the age of the thousands of objects scattered across the image is just one of the exciting challenges scientists face. And the longer researchers look into the deep field, the more strange and wonderful things they discover.
For example, Gaudí pointed to an orange N-shaped galaxy zigzagging to the right of a perfect spiral galaxy that appears to have been deformed and warped by an intense cosmic collision. Gaudí called it the “train merger crash galaxy” for its chaotic and disorderly appearance.
With the first images only a few days old and more than 20 years of fuel aboard the JWST, the discoveries have only just begun. We hope you enjoy getting lost in space.
Originally published on Live Science.
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