NASA’s JWST Hunts Dark Matter in Stunning Image of Bullet Cluster

For astronomers who study dark matter, the ball group is one of the largest laboratories in the universe.

It was discovered almost by accident, a stroke of X rays in the sky which was detected by the Einstein Observatory of NASA in 1992 and received the designation 1st 0657-56. The follow -up observations in the visible light confirmed that it was a group of galaxies – a swarm of dozens, even hundreds of galaxies, all linked together by gravity and orbit around a common center. The 1st 0657-56 cluster is decently far from the earth; The light that we see left it about four billion years ago.

The cluster is not only a simple system of galaxies. There is a main cluster, large and somewhat lying down, with a more compact and spherical subclusive on one side, separated from more than 1.5 million light years. Note that the large galaxy closest to our own Milky Way is Andromeda galaxy, 2.5 million light years old. Imagine having dozens of galaxies in our sky less than half of this distance!

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Deeper observations of 1st 0657-56 taken using the Chandra X-ray observatory revealed that the cluster was loaded with hot gas, and I mean hot: The majority were tens of millions of degrees Celsius. This is common in the clusters of galaxies, where such a gas is generally supposed to be overheated by raw radiation from supermassive black holes, as well as the enormous amount of kinetic energy absorbed when the galaxies zoom in the cluster.

But the gas in 1st 0657-56 had an odd structure. Like the cluster itself, it was divided into two main clouds, both located between the main cluster and the subclusive. The largest cloud, closer to the main heap, was elongated and diffuse. But the other, closer to the compact subclusive, was smaller and had a characteristic arc shock shape, a dull cone similar to the wake left for a ship moves in the water.

This meant that 1st 0657-56 was not a single cluster but in fact two Clusters that recently collided-“recent” on a cosmic scale, that is to say: about 200 to 100 million years ago. The collision occurred at a breathtaking speed, the two clusters slamming at a relative speed of about 4,000 kilometers per second. This represents more than 1% of the speed of light!

The conical form of gas has given the sound system nickname the bullet cluster, which is also appropriate because the second cluster is smaller than the other and seems to have exploded through it.

The galaxies are small compared to the size of the bullet cluster, so very few galaxies which have physically entered it. In a sense, the two small constituent groups of this cosmic object went through each other. But the hot gas which impregnated the space between the galaxies in each cluster would have crushed head on. While the galaxies slipped relatively unscathed, this hot gas was considerably slowed down by the collision. This is why most gas is located between the two clusters of galaxies; He was left to the Smashup scene between the two flight systems.

But there is more in the group of bullets that does not meet the eye.

For decades, astronomers have raised many evidence of the existence of dark matter – a mysterious substance which has mass and gravity but does not emit any light and rarely, if never, interacts with normal matter.

On the cosmic scales, dark matter betrays its presence via its severity. The speed at which the stars have adorned in a galaxy depends on the gravity they feel of the galaxy as a whole, which in turn depends on the mass it has-that is to say the amount of matter it contains. The stronger the mass, the stronger the gravity, and the more a star moves quickly. American astronomers Vera Rubin and Kent Ford used this principle in the 1970s to show that the stars in the external part of Andromeda galaxy moved far too quickly, given the measured mass of Andromeda. This implied that there was a halo of dark matter in which the galaxy was anchored.

Something similar has been seen in many clusters of galaxies: galaxies move far too quickly for the calculated mass of their domestic cluster. They should fly away in space, but instead, they remain in orbit, which implies that there is much more mass to these clusters than we cannot see.

Whatever the dark matter, we do not think of interacting with normal matter, except by gravity, and it should also not interact well even with itself. This means that if you have two collision objects surrounded by dark matter, these halos will pass through the other and continue in space.

You probably see where it goes: the group of bullets is exactly this kind of situation, an experience of dark matter while waiting for us to examine. However, the detection of dark matter requires a gravitational tip.

When a beam of light goes through an object with mass, the gravity of this object will fold the path of the light radius. For very massive or dense objects, light can bend considerably. For example, light from a background galaxy can be deformed in an arc-shaped or be divided into several images. This phenomenon is called a strong gravitational lens because it acts a lot like a glass lens.

If the severity of a lens is not as strong, it can still slightly distort the image of a background galaxy, but it is difficult to know how distorted any individual galaxy could be. This type of low gravitational lens can be statistically detected, however, by examining a large number of background galaxies and by measuring their forms.

Astronomers have mapped the weakly Lensée galaxies seen behind the ball group, which they then used to draw the position of the dark matter of the cluster. What they found was incredible: there was a huge excess mass surrounding the two subclusive! This meant that the halos of the dark matter of the subclusive passed from each other, as well as the theory predicted it.

For this reason, the heap of bullets is considered by almost all astronomers as the smoking pistol (very expected word game) to the existence of Dark Matter, especially in the halos surrounding galaxies and clusters.

But scientists have not finished examining the cluster. An international team of astronomers observed it with the James Webb space telescope (JWST), which allowed them to see many more distant background galaxies, which in turn allowing them to map the dark matter using the gravitational lens in more detail. They published their results in the Astrophysical newspaper letters in June 2025.

The JWST field of vision is a bit small, so they did not observe the whole cluster, but they were always able to assess its mass and note that the entire cluster – stars, hot gas, black matter and everything – contains several hundred billions of times the mass of the sun. It is actually smaller than previous estimates, which can be partly linked to the smallest field of vision of JWST, but can also be a real result based on its clearer vision. The team is currently working on analysis of JWST data and the huge black energy camera to see if they can refine the mass estimate.

Researchers also note that JWST data show that the elongated main cluster contains at least three tufts of galaxies, while a more fluid distribution is expected. This means that the main cluster may have undergone other collisions recently, still complicating the already complex history of the ball cluster.

Invisible dark matter can be, but that does not mean undetectable. And whenever we run a new shoe cluster telescope, we learn more. We end on Dark Matter, and soon, we hope, its voters will be illuminated.