“Every good thing has an end.” This saying is valid both in space and on Earth. We are aware that stars, like everything else, must die. When their cores run out of fuel for nuclear fusion, stars of all sizes collapse under their own gravity and die to form a dense cosmic remnant such as a white dwarf, neutron star, or black hole. Our own star, the Sun, will share this fate in about 5 billion years, initially growing into a red giant and destroying the inner planets, including Earth. In about 1 billion years, this phase will also end and the Sun’s core will turn into a white dwarf ember surrounded by a cloud of cosmic ash in the form of cooling star material.

Scientists have developed the Hertzsprung-Russell diagram, which shows stellar life, afterlife, and death. This scheme is followed throughout the evolution of stars of all masses, from hydrogen-burning main sequence stars to dense cosmic remnants. But a new study suggests that some stars at the heart of our galaxy may not live up to our best models of stellar life and death. These stars may have fed on dark matter, the most mysterious substance in the universe, to effectively give themselves cosmic immortality; this may require the creation of a “dark Hertzsprung-Russell diagram”.

“The galactic center of the Milky Way is a very extreme environment, very different from where we are in the Milky Way,” research team leader Isabelle John of the Kavli Institute for Particle Astrophysics and Cosmology told Space.com. “The stars closest to the center of the galaxy, the so-called ‘S cluster stars,’ are a great mystery.

“They show a range of properties that are not available anywhere else: it is not clear how they got so close to the centre

John added that these S cluster stars, located about three light-years from the very heart of our galaxy, appear to be much younger than would be expected if stars had migrated to the region from other parts of the Milky Way. “Even more surprising is that not only do the stars appear extremely young, but there are also fewer older stars,” he continued, “many heavy stars.”

John and his colleagues suggest that the reason for these unusual features may be that these stars accumulate large amounts of dark matter, which is then destroyed within them. This process could provide them with a completely new and unexpected type of fuel.

“Our simulations show that stars can survive with only dark matter as fuel, and since an extremely large amount of dark matter is located near the Galactic Center, these stars become immortal,” John added. “This is very exciting because our simulations show results similar to observations of S-cluster stars: dark matter as fuel will keep stars young forever.”

John continued: “The idea of ​​immortal stars could immediately explain many of the unusual properties of S cluster stars. If stars in the Galactic Center become immortal due to the high density of dark matter, this could explain the unusual abundance of apparently young stars in the Galactic Center, as well as the presence of older stars.” It may also explain its absence.”

Dark matter is its own worst enemy

Dark matter is a problem for physicists because it is estimated to make up 85% of the universe and because it does not interact with light, we cannot see it. Additionally, dark matter does not appear to interact with “ordinary matter.” This everyday matter consists of protons, neutrons, and electrons and includes all stars, planets, moons, asteroids, comets, gases, dust, and living things in the universe.

Scientists can only infer the existence of dark matter because it interacts with gravity, and this interaction can affect ordinary matter, even light. But if interactions between dark matter and ordinary matter do occur, they are rare and weak; Scientists do not believe we have discovered such an interaction.

What is less certain is whether dark matter interacts with itself. To understand what this means, remember that all ordinary matter particles have a version of antimatter. For example, for a negatively charged electron there is a positively charged antiparticle called a positron. When matter and antimatter meet, they destroy each other and energy is released.

“The annihilation of dark matter is similar to the annihilation of matter and antimatter: If a particle and its antiparticle meet, they annihilate and form other particles, such as photons. Similarly, dark matter particles can annihilate in this way,” said John. “In many dark matter models, “A dark matter particle is considered its own antiparticle, which means that any two dark matter particles can annihilate each other.”

But we don’t see dark matter disappearing, so it must be pretty rare. This means this would be more likely in an environment where large amounts of dark matter are clumped together, John says. Perhaps the superdense region at the heart of the star is where gravity is strongest, where dark matter actually interacts.

Could the sun also be immortal?

Main sequence stars burn hydrogen in nuclear fusion processes throughout their lives. This creates an outward “radiation pressure” that balances the helium, which makes up most of the star’s energy, and the push of the star’s own gravitational forces. This cosmic tug of war between radiation pressure and gravity continues for millions, even billions of years, keeping these stars in stable balance.

“For most of a star’s life, these processes occur primarily in the star’s core, where the gravitational pressure is highest,” John said. “We showed that if stars accumulate large amounts of dark matter and this then disappears inside the star, this can also create an outward pressure and stabilize the star through dark matter destruction rather than nuclear fusion. That means stars can use dark matter as fuel instead of hydrogen.”

“Stars are running out of hydrogen, which eventually leads to their death. Dark matter, on the other hand, could be accumulating continuously, making these stars immortal.”

So, can the Sun gift itself immortality by switching to this alternative fuel source? John thinks not. Located in the middle of one of the Milky Way’s spiral arms, this dark fountain of youth is in the wrong place in our galaxy to reach.

“Stars need a very large amount of dark matter to effectively replace fusion. In most of the Milky Way, the density of dark matter is not high enough to significantly affect stars. But at the center of the Galaxy, the density of dark matter is very high, potentially billions of times higher than on Earth, providing the amount of dark matter needed to make stars immortal,” John explained. “So our sun is not immortal.”

John added that the team’s findings potentially reveal many secrets about dark matter itself and the immortal stars it could feed.

“Our findings show us that dark matter can co-exist with ordinary particles, which is necessary to slow down and capture dark matter particles inside a star, and that dark matter particles can destroy each other,” he said. “By observing the distribution of immortal stars around the Galactic Center, we will also gain some insight into the distribution and density of dark matter around the Galactic Center.”