How dark stars could illuminate the early universe

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Scientists working with the James Webb Space Telescope discovered three unusual astronomical objects in early 2025, which maybe examples of dark stars. The concept of dark stars has been around for some time and could change scientists’ understanding of how ordinary stars form. However, their name is somewhat misleading.

“Dark Stars” is one of those unfortunate names that, on the surface, does not accurately describe the objects they represent. Dark stars aren’t exactly stars, and they’re certainly not dark.

Yet the name reflects the essence of this phenomenon. The “dark” in the name does not refer to the brightness of these objects, but to the process that causes them to glow – driven by a mysterious substance called dark matter. The sheer size of these objects makes it difficult to classify them as stars.

As a physicist, I was fascinated by dark matter and tried to find a way to see it. traces using particle accelerators. I’m curious if dark stars could provide an alternative method of finding dark matter.

What makes dark matter dark?

Dark matterwhich makes up about 27% of the universe but cannot be observed directly, is a key idea behind the phenomenon of dark stars. Astrophysicists have been studying this mysterious substance for almost a century, but we have seen no direct evidence of it aside from its gravitational effects. So what makes dark matter dark?

Humans above all observe the universe by detecting electromagnetic waves emitted or reflected by various objects. For example, the moon is visible to the naked eye because it reflects sunlight. Atoms on the moon’s surface absorb photons – particles of light – sent from the sun, causing the electrons in the atoms to shift and send some of that light back towards us.

More advanced telescopes detect electromagnetic waves beyond the visible spectrumsuch as ultraviolet, infrared or radio waves. They use the same principle: the electrically charged components of atoms react to these electromagnetic waves. But how can they detect a substance – dark matter – that not only has no electrical charge, but also contains no electrically charged components?

Although scientists do not know the exact nature of dark matter, many models suggest that it is made of particles that are electrically neutral, that is, without an electrical charge. This trait makes it impossible to observe dark matter in the same way as ordinary matter.

Dark matter is thought to consist of particles that are their own antiparticles. Antiparticles are “mirror” versions of particles. They have the same mass but opposite electric charge and other properties. When a particle meets its antiparticle, both annihilate each other in a burst of energy.

If dark matter particles were their own antiparticles, they would annihilate by colliding with each other, potentially releasing large amounts of energy. Scientists predict that this process plays a key role in the formation of dark stars, provided that the density of dark matter particles inside these stars is high enough. Dark matter density determines how often dark matter particles meet and annihilate each other. If the density of dark matter inside dark stars is high, they will frequently annihilate.

What makes a black star shine?

The concept of dark stars arises from a fundamental question still unresolved in astrophysics: How stars form? According to the widely accepted view, the primordial clouds of hydrogen and helium — the chemical elements formed in the first minutes after the Big Bangabout 13.8 billion years ago – collapsed under the influence of gravity. They warmed up and nuclear fusion initiatedwhich heavier elements formed hydrogen and helium. This process led to formation of the first generation of stars.

In the standard view of star formation, dark matter is seen as a passive element that simply exerts a gravitational pull on everything around it, including primordial hydrogen and helium. What if dark matter played a more active role in the process? This is exactly the question that a group of astrophysicists trained in 2008.

In the dense environment of the early universe, dark matter particles collide and annihilate each otherreleasing energy in the process. This energy could heat hydrogen and helium gas, preventing them from collapsing further and delaying or even preventing the ignition typical of nuclear fusion.

The result would be a star-like object – but powered by heating dark matter instead of fusion. Unlike ordinary stars, these dark stars could live much longer because they would continue to shine as long as they attracted dark matter. This feature would distinguish them from ordinary stars, as their cooler temperature would result in reduced emissions of various particles.

Can we observe black stars?

Several unique features help astronomers identify potential dark stars. First, these objects must be very old. As the universe expands, the frequency of light from objects far from Earth are decreasingmoving toward the infrared end of the electromagnetic spectrum, meaning it is “red-shifted.” THE the oldest objects appear the most redshifted to observers.

Since dark stars form from primordial hydrogen and heliumthey are expected to contain little or no heavier elements, such as oxygen. They would be very large and cooler on the surface, but very bright because their size – and the light-emitting surface area – compensates for the lower brightness of their surface.

They are also expected to be enormous, with radii of around tens of meters. astronomical units — a measure of cosmic distance equal to the average distance between the Earth and the sun. The theory is that some supermassive dark stars reach masses about 10,000 to 10 million times that of the sun, depending on how much dark matter and hydrogen or helium gas they can accumulate as they grow.

So, have astronomers observed dark stars? Maybe. Data from the James Webb Space Telescope has revealed very high redshift objects that appear brighter – and perhaps more massive – than scientists expect from typical early galaxies or stars. These results have led some researchers to propose that dark stars could explain these objects.

Dark stars could explain the first black holes

What happens when a dark star runs out of dark matter? It depends on the size of the black star. For the lightest dark stars, the depletion of dark matter would mean that gravity compresses the remaining hydrogen, thereby triggering nuclear fusion. In this case, the dark star would eventually become an ordinary star, so some stars might have started out as dark stars.

Supermassive dark stars are even more intriguing. At the end of their lifespan, a dead supermassive black star would collapse directly into a black hole. This black hole could initiate the formation of a supermassive black holelike those that astronomers observe at the centers of galaxies, including ours. Milky Way.

Dark stars could also explain how supermassive black holes formed in the early universe. They could shed light on some unique black holes observed by astronomers. For example, a black hole in the galaxy UHZ-1 has a mass close to 10 million solar masses and is very old: it formed only 500 million years after the Big Bang. Traditional models struggle to explain how such massive black holes could form so quickly.

The idea of ​​dark stars is not universally accepted. These candidate dark stars could yet turn out to be simply unusual galaxies. Some astrophysicists argue that matter accretion, a process in which massive objects attract surrounding matter – can alone produce massive stars, and that studies using observations from the James Webb Telescope cannot distinguish between ordinary massive stars and less dense, cooler dark stars.

The researchers emphasize that they will need more observational data and theoretical advances to solve this mystery.