Will neutron stars last forever?

Almost everyone has an image in their mind when it comes to the universe, right? Stars twinkling or enormous black holes lying somewhere deep in the vast space. But there is  another celestial body, more mysterious—far denser—and, in some respects, much more interesting: the neutron star. These stellar remnants born from the death of a supernova, leaving behind an extremely dense core that would weigh almost a billion tons per teaspoon. Neutron stars are extremely stable, but this raises a major question mark: do they last indefinitely?

In this article, we take a closer look at neutron stars: Are they as immortal as they appear to be? In this post, we will cover the aspects of neutron stars that make them special, why they live so long, and what could possibly kill one. So, join us now on this odyssey into the always odd and many times everlasting world of neutron stars!

What is a Neutron Star?

How neutron stars even exist in the first place helps explain their longevity. A neutron star is produced from the explosive death of a massive star. A dying star is when a star, much more massive than our own sun, has a supernova explosion blowing away most of their outer layers. It leaves behind a dense core, which collapses under its own gravity to become a neutron star.

A neutron star is a very small but very dense ball of neutrons (hence the name). On a neutron star, the gravity is so strong in fact that it pushes protons and electrons together to fuse into neutrons. Following this process provides them some unique features, including:

• Extremely dense: While the mass of a neutron star can equal that of the Sun, its diameter may be only 20 km across.
• Extreme magnetic fields: Neutron stars can have magnetic fields that are trillions of times stronger than the Earth, causing them to emit powerful beams of radiation.
• Fast rotation: A neutron star known as a pulsar rotates with astonishing speed, often several hundred times a second, emitting beams of radiation like a galactic lighthouse.

Under such brutal conditions, neutron stars are made to last. The question really is, how long will they stand up to the forces of the universe?

Length of Life for a Neutron Star

Neutron stars are different from regular ones in that the neutron star doesn’t actually burn fuel, meaning it never really goes through a regular stellar life. They are not stirred in consequence, their state is stable until they should be disrupted. The force binding neutron stars is called neutron degeneracy pressure. It is a quantum mechanical phenomenon that prevents neutron stars from being squeezed ever closer together. A powerful force that can balance the star’s incredible gravity to stop it from becoming a black hole.

Thanks to this equilibrium, a neutron star never ages as we usually think of it. That stability allows it to survive for trillions of years, much more than the lifespans of regular stars. Indeed, neutron stars could outlast every living star in the universe and silently glow across the cosmos long after galaxies have dissolved to nothing.

Fun fact: A neutron star will only further collapse into a black hole if it becomes more massive than what is called the Tolman–Oppenheimer–Volkoff (TOV) limit. Above this mass limit (roughly 2-3 times the mass of the Sun), a neutron star cannot support itself and collapses to form a black hole.

Challenges to Neutron Star Stability

Neutron stars are very stable indeed, but they do not remain unaffected by external factors. Now, here are a few cosmic events that might change the status quo of a neutron star — or even obliterate one.

• Collisions with other stars or black holes: When a neutron star comes into contact with another neutron star, or some heavier black hole, it usually results in a violent merger. If two neutron stars collide, depending on the mass combination this leads either to a larger neutron star or may also create a black hole.
• Material Accretion – Neutron Stars can sometimes accumulate material from a close by accomplice star, gradually extending mass. When a neutron star mass exceeds the TOV limit the neutron star collapses into black hole.
• Magnetars — Some neutron stars are so highly magnetized that they are termed “magnetars.” Starquakes, magnetic outbursts that occur on magnetars and emit massive energy impulses. These don’t actually kill the neutron star, but they do indicate that magnetars could have different lifecycles or death than normal neutron stars.

Fun fact: Neutron-capture nucleosynthesis in colliding neutron stars is also responsible for the formation of some of the heaviest elements in the universe, including gold and platinum!

Do Neutron Stars “Die”?

Neutron stars do change, but very slowly over time. A young neutron star spins fast and radiates a lot of energy but slows down and cools gradually as it gets older. It will eventually cease to emit detectable radiation after trillions of years, and settle down into a state known as a black dwarf—almost an entirely inert body that is little different than the cold dark background of space. This would be the last  “death”  stage of a neutron star but even this process is extremely slow. Indeed, the Universe is too young for any neutron star to have gone through this black dwarf phase yet.

Neutron stars might break down even more, but over time scales so long that is beyond our imagination, through proton decay — a hypothetical process in which the subatomic particles decay into other particles. In reality, however, if this decay process is real all that is left behind of a neutron is a haze of particles that at the end will fade away.

What Happens to Neutron Stars in the Far Future?

Neutron stars could be some of the very last remaining things in the universe far into its future. The expansion of the universe continues, stars burn out and galaxies will eventually lose their light; alone, only neutron stars remain. This is known as the black dwarf era. Only black holes and neutron stars will survive to the end of time after all other stars have long since gone cold in a state termed by scientists as the “heat death” of the universe, where every bit of order has been driven into maximum entropy and no useful energy remains.

Even neutron stars will slip away into nothingness in the far, far future as particles within neutron stars eventually decay. Their final endings are related to the end of all time, making them the conclusion of a story that started with a stellar explosion.

Summary

Therefore, does it mean that neutron stars will last forever? In a sense, yes. They are so stable they can survive, for trillions of years – perhaps longer than any other stars in the universe. Though even these stellar giants would one day meet their demise, leaving nothing but faint traces in a quiet, dark universe.

One of the odd and attractive things about neutron stars, is they exemplify just how bizarre, yet fascinating, the universe really is. Forged in cataclysmic supernovae, yet they persist with an astonishing stability, bearing that final fleck of light in a universe that’s winding down. Neutron stars provide a window not just into the history of the universe but its distant future. They are kind of like timestamps, both signifying the passing of time and signaling the eventual end.

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