On July 12, NASA shared the first images of the fully operational system. 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. Bursting with twinkling stars, distorted streaks of light and thousands upon thousands of gem-like galaxies shimmering in the dark of space, the image was billed as the deepest image of the universe never taken.
That is, to put it simply, a lot to take in.
“You start looking at this image and realize there’s no empty sky,” Scott Gaudi, professor of astronomy at Ohio State University, told Live Science. “Something crazy is going on everywhere.”
To try and understand this historic picture a little better, we asked Gaudi to walk us through 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 group 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, which lies about 4.6 billion light-years away. Earth – meaning that the light we see here was emitted shortly before our planet was formed. You can see the cluster as a series of bright points of light in the center of the image, surrounded by a flecked white halo of more diffuse starlight.
Galaxy clusters are among the largest gravitational 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, a real mess ensues. Vast clouds of star-forming gas collide, compress and heat up, forming countless new stars that “spit up” colliding galaxies, Gaudi said.
These spewed stars — which likely number in the millions, if not billions, and are not gravitationally bound to any of the galaxies in the cluster — create a white haze known as intra-cluster light.
JWST shows us this light in greater detail than ever before, adding evidence to a long-held theory that galaxy clusters store much of their mass in these intra-cluster regions, Gaudi said.
A cosmic magnifying glass
Mass is precisely what makes 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 behind it (compared to our view from Earth). This leads to the next key feature of the JWST deep field image – the gravitational lens.
“The next thing that will probably catch your eye is these weird worm-like arcs that kind of emanate from the center of the image,” Gaudi said. “These are background galaxies that sit behind the foreground cluster. Once their light reaches the cluster, the mass of the cluster bends that light and creates what is called a gravitational lens. .”
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Like the cosmic combination of a magnifying glass and a funerary mirror, gravitational lenses both distort and amplify the light from background galaxies. If you imagine the center of this image as a clock, you can clearly see two of these background galaxies located between 2 and 3 o’clock, and 7 and 9 o’clock, respectively.
These two galaxies appear as bright orange curved lines that wrap around the central galaxy cluster. They seem incredibly long – longer even than the massive central cluster – because their light is amplified dramatically. Despite appearing vast and looming, the galaxies are actually more than 13 billion light-years away, Gaudi said, potentially making them one of the oldest observable galaxies in the universe.
But the mass of the central cluster not only magnifies these ancient objects, it also doubles them. Look a little closer and you’ll see that the two distorted orange lines are brighter around the edges and darker in the middle. Look even closer at one of the orange lines and you will see that the two bright regions are actually perfect mirror images of each other.
It’s a telltale byproduct of gravitational lensing, according to Gaudi – a galaxy, split into multiple images that curve around the same center of mass. Gaudi added that almost all of the distorted objects on display here have a mirror image elsewhere in the field.
Studying the oldest light in the universe is one of NASA’s key goals for JWST. But, as this image shows, the mighty telescope can’t look back without thousands upon thousands of younger, closer galaxies bombarding the frame.
In general, the large, bright six-pointed objects in the foreground of the image are stars. Almost everything you can see is a galaxy or cluster of galaxies, 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 will see a perfect spiral galaxy, just like ours Milky Way. Spiral galaxies are active galaxies that form stars, Gaudi said, and they tend to be filled with hotter, younger stars that glow in 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: a fiery orange elliptical galaxy.
“Elliptical galaxies are kind of dead,” Gaudi said. “They’ve already formed all of their stars. The massive blue stars die first, and only the old red stars remain.”
Generally, the bluest galaxies in this image are younger spiral galaxies, while the reddest galaxies are old, dead elliptical galaxies.
However, the color of a galaxy can also be changed by its distance from the telescope, thanks to a phenomenon called redshift. Basically, as light travels through the vast and expanding universe, its wavelength gradually increases with distance, becoming increasingly red with time. So some of the red and orange galaxies in this image are actually old background galaxies whose light has been redshifted into the path of JWST’s lens.
Estimating the age of the thousands of objects dotted across this image is just one of the exciting challenges facing scientists. And the longer researchers stare into the deep field, the more weird and wonderful things they will discover.
For example, Gaudi pointed to an orange N-shaped galaxy zigzagging just to the right of the perfect spiral galaxy, seemingly distorted and twisted by an intense cosmic collision. Gaudi dubbed it the “Fusion Train Wreck Galaxy” for its chaotic and confusing appearance.
With the first images only days old and more than 20 years of fuel waiting aboard the JWST, the discoveries are just beginning. We hope you enjoy getting lost in space.
Originally posted on Live Science.