Neutron Stars: The Dying Giants of the Universe

Neutron stars are one of the smallest but most fascinating objects in the universe. These celestial objects are incredibly dense, with a mass greater than our sun packed into an area the size of a city. Due to their extreme nature, neutron stars undergo a variety of dramatic processes, such as emitting intense radiation and producing powerful magnetic fields. In this discussion, we’ll explore what happens to neutron stars and the different processes they undergo over time.

The Birth of Neutron Stars

Neutron stars are the remnants of massive stars that have undergone a supernova explosion, leaving behind a dense, compact core. When a massive star has exhausted its fuel, it undergoes a catastrophic collapse, causing its core to implode. The implosion generates an immense amount of energy, which subsequently explodes outwards, creating a supernova. The outer layers of the star are blown away, leaving behind a super-dense core known as a neutron star.

The Properties of Neutron Stars

Neutron stars are incredibly dense, with a mass up to twice that of the sun, yet only around 10 to 15 kilometers in diameter, making them one of the smallest but densest objects in the universe. This density is so high that 1 cubic centimeter of a neutron star would weigh as much as 100 million elephants. Due to their small size and high density, neutron stars have incredibly strong gravitational fields. At their surface, the gravitational pull is around 200 billion times stronger than that of the Earth.

The Discovery of Neutron Stars

The concept of neutron stars was first proposed in 1934 by Austrian physicist Walter Baade and Swiss astrophysicist Fritz Zwicky. However, it wasn’t until 1967 that the first neutron star was discovered. Jocelyn Bell Burnell, a graduate student at Cambridge University, discovered regular radio wave pulses coming from a particular point in the sky. These pulses, which were incredibly precise and consistent, were later identified as emanating from a rapidly rotating neutron star. Burnell’s discovery led to the coining of the term “pulsar” to describe these types of neutron stars.

The Life of a Neutron Star

Key Takeaway: Neutron stars are incredibly dense, small, and have strong gravitational fields due to their properties, making them fascinating objects to study. They are born from the remnants of massive stars that have undergone a supernova explosion, leaving behind a dense, compact core. Neutron stars can emit intense radiation and undergo a second supernova explosion, generating gravitational waves. The cooling process of a neutron star takes an incredibly long time (around 10^15 years), and it can become a black dwarf.

Cooling Down

Neutron stars are born incredibly hot, with temperatures reaching up to a million degrees Celsius, but they cool down rapidly. Within just a few decades, their surface temperature drops to around a million degrees Kelvin, and within a few hundred thousand years, it drops to around 10,000 Kelvin. At this point, the neutron star stops emitting significant amounts of thermal radiation and begins to cool much more slowly.

Magnetic Fields

Neutron stars have incredibly strong magnetic fields, which can be up to a billion times stronger than the Earth’s magnetic field. These magnetic fields can cause charged particles within the star to accelerate to near-light speeds, producing intense radiation in the form of X-rays and gamma rays. Neutron stars that emit this type of radiation are known as magnetars.


Some neutron stars are part of a binary system, where they orbit around another star. In these systems, the neutron star can accrete matter from its companion star, which can cause it to emit X-rays and gamma rays. This process can continue until the neutron star is completely consumed by its companion star, or until it explodes in a supernova.

Black Holes

If a neutron star is part of a binary system, and its companion star is also a massive star, then it too can go supernova. If the resulting core is more than three times the mass of the sun, it will collapse into a black hole. In this scenario, the neutron star will be consumed by the black hole, and its matter will be absorbed by the black hole’s event horizon.

The Death of Neutron Stars

Black Dwarf

Eventually, a neutron star will cool down to the point where it no longer emits any significant radiation. At this point, it will become a “black dwarf.” However, this process takes an incredibly long time, around 10^15 years, which is longer than the current age of the universe. Therefore, no black dwarfs currently exist, and it’s unlikely that any will ever be observed.


In some cases, a neutron star can undergo a second supernova explosion. This can happen if the star accretes matter from its companion star, causing it to exceed a critical mass. If this happens, the neutron star will undergo another catastrophic collapse, causing another supernova explosion. This process can repeat itself multiple times, leading to a series of supernovae known as a supernova chain reaction.

Gravitational Waves

When a neutron star undergoes a supernova explosion, it can generate gravitational waves, ripples in the fabric of spacetime. These waves travel at the speed of light and can be detected by gravitational wave observatories. In 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves from the merger of two neutron stars, providing further evidence of the existence of these objects.

FAQs: What Happens to Neutron Stars

What is a neutron star?

A neutron star is a tiny, incredibly dense remnant of a supernova explosion. It is made up almost entirely of neutrons, which are subatomic particles that make up the nuclei of atoms. Neutron stars are among the most exotic objects in the universe, and they are incredibly dense – one teaspoon of neutron star material would weigh around six billion tons.

What happens to a neutron star over time?

Over time, a neutron star will continue to cool down and release energy in the form of radiation. This is because neutron stars are incredibly hot when they are first formed, but they gradually cool down over time. Eventually, the neutron star may become so cold that it no longer emits any radiation at all.

Can neutron stars disappear completely?

It is unlikely that a neutron star will disappear completely. Neutron stars are incredibly stable and long-lasting, and they can exist for billions of years. However, if a neutron star collides with another object – such as another neutron star or a black hole – it may be destroyed in a violent explosion. This type of event is called a kilonova or a gravitational wave event.

What happens when a neutron star collides with another object?

When two neutron stars collide, they can create a massive explosion that releases huge amounts of energy. This type of event may be visible as a bright burst of light in the sky, known as a gamma-ray burst. If a neutron star collides with a black hole, it may be torn apart by the black hole’s immense gravity.

Can neutron stars turn into black holes?

Neutron stars can turn into black holes under certain conditions. If a neutron star accretes enough material from a nearby star or if it merges with another neutron star, it may eventually become so massive that it collapses into a black hole. However, this process takes a very long time – billions of years – so it is unlikely to happen in the foreseeable future.

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