25 Neutron Stars Facts That Will Make You Spell-Bound

A neutron star has the potential to destroy a solar system due to its strong magnetic and gravitational fields.

A neutron star is extremely hot (up to 100 billion K) when it is newly formed before it cools down. Also, it has a high rotation rate; the fastest rotating neutron star rotates 43,000 times every minute.

There could be 100 million neutron stars in the Milky Way, but astronomers have detected less than 2000 as the majority of them are over a billion years old and have cooled down with time. The existence of neutron stars depends on their mass. Usually, the mass of a neutron star is less than two solar masses. If the approximate mass of a neutron star is more than three solar masses, it will end up as a black hole.

What are neutron stars?

Neutrons stars are small stars born when a larger massive star collapses in a supernova explosion.

To simplify, a neutron star is the remaining core of a giant star that has collapsed. When this happens, the electrons and protons get merged and form neutrons that constitute about 95 % of a neutron star.

Neutron stars could last as long as 100,000 years or even up to 10 billion years.

The initial temperature of a neutron star could touch 100 billion K, but it cools down quickly to 10 million K in a few years.

Astronomers Walter Baade and Fritz Zwicky had predicted the existence of neutron stars in 1934, three decades before the first neutron star was confirmed.

A group of seven isolated neutron stars which are closest to the Earth has been given the name 'The Magnificent Seven.' They are located in the range of 390-1630 light-years.

Origin And Formation Of Neutron Stars

The origin and the subsequent formation of neutron stars lead to various fascinating facts.

During the last stage of a star's life, it meets with a supernova explosion leading to the core being squeezed out with the help of a gravitational collapse. This remaining core is further classified depending on its mass.

If this core is a massive star, it becomes a black hole. And if it is a low-mass star, it turns up as a white dwarf (a dense star about the size of a planet). But if the remaining core falls between massive stars or low-mass stars, it would end up as a neutron star.

During the explosion, when the core of the giant star collapses, electrons and protons melt into each other and form neutrons.

A neutrons star is said to be made of 95 % neutrons.

These neutron stars have a high rotation rate when they are newly formed due to the law of conservation of angular momentum.

PSR J1748-2446ad, which is the fastest rotating neutron star discovered, is estimated to rotate 716 times per second or 43,000 times per minute.

With time, neutron star slows down. They have a rotation range from 1.4 milliseconds to 30 seconds.

These rotations can further increase when the neutron star exists in a binary system as it could attract accreted matter or plasma from its companion stars.

After its formation, a neutron star does not keep generating heat but cools down with time, unless it evolves further when there is a collision or accretion.

Types Of Neutron Stars

Neutrons stars are divided into three types depending on their features: X-ray pulsars, magnetars, and radio pulsars.

X-ray pulsars are neutron stars that exist in a binary star system when two stars orbit each other. They are also called accretion-powered pulsars; they derive their source of power from their more massive companion star's material, which then works with their magnetic poles to emit high-powered beams.

These beams are seen in the radio, X-ray spectrum, and optical. A few sub-types of X-ray pulsars include millisecond pulsars that spin about 700 times per second, compared to the spin of 60 times per second of normal pulsars.

Magnetars are differentiated from other neutron stars by their strong magnetic field. Although its other features such as radius, density, and temperature are similar, its magnetic field is a thousand times stronger than an average neutron star. As they have a strong magnetic field, they take longer to rotate and have a higher rotation rate compared to other neutron stars.

Radio pulsars are neutron stars that emit electromagnetic radiation, but they are very difficult to find. This is because they can only be seen when their radiation beam is directed towards the Earth. And when that happens, the event is called the 'lighthouse effect,' as the beam appears to come from a fixed point in space.

Scientists have estimated that about 100 million neutron stars are present in the Milky Way as per the number of supernova explosions that have happened in the galaxy.

However, scientists have managed to discover less than 2000 pulsars, which are the more common types of neutron stars. The reason is attributed to the age of pulsars, which is billions of years, giving them enough time to cool down. Also, pulsars have a narrow field of emissions, making it difficult for satellites to pick them up.

Characteristics Of Neutron Stars

Neutron stars have unique characteristics that make them stand out.

A neutron star's surface temperature is 600,000 K, which is 100 times more than the Sun's 6,000 K.

A neutron star cools down quickly as it emits such large numbers of neutrinos that take away the majority of the heat. An isolated neutron star can cool down from its initial temperate of 100 billion K to 10 million K in just a few years.

Its mass ranges from 1.4-2.16 solar masses, and that is 1.5 times the mass of the sun.

A neutron star, on average, has a diameter of 12-17 mi (19-27 km).

One of the important facts about neutron stars is that if the neutron star has more than three solar masses, it could end up as a black hole.

Neutron stars are extremely dense, with a teaspoon of them weighing about a billion tons. However, the density of a star decreases if its diameter increases.

Neutron stars' magnetic and gravitational fields are quite powerful compared to the Earth. Its magnetic field is one quadrillion times, and its gravitational field is 200 billion times stronger than the Earth.

The strong magnetic pole and gravitational field could wreak havoc if the neutron star comes closer to the Solar System. It could throw planets out of their orbits and raise tides to destroy the Earth. However, a neutron star is too far to make an impact, with the closest being 500 light-years away.

Neutron stars can also exist in a complex binary star system where they are paired up with another neutron star as a companion star, red giants, white dwarfs, main-sequence stars, or other stellar objects.

A binary system with two pulsars orbiting each other was discovered in 2003 by astronomers in Australia. It was called PSR J0737−3039A and PSR J0737−3039B.

It is estimated that about 5% of all neutron stars are part of the binary star system.

Hulse-Taylor binary, or PSR B1913+16, is the first-ever binary pulsar existing with a neutron star. It was discovered in 1972 by Russell Alan Hulse and Joseph Hooton Taylor, Jr., whose discovery and further studies earned the two scientists Nobel Prize in Physics in 1993.

Under the binary star system, two neutron stars that orbit each other could come close to colliding and meet their doom. When this happens, it is called a kilonova.

This was first detected in 2017 in research that also led to a conclusion that the source of the universe's metals such as gold and platinum is due to the collision of two neutron stars.

Neutron stars can have a planetary system of their own, as they could host planets. So far, only two such planetary systems have been confirmed.

The first such neutron star that has a planetary system is PSR B1257+12, and the second is PSR B1620-26. However, these planetary systems are unlikely to aid life as it receives less visible light and high amounts of ionizing radiation.

A pulsating neutron star could experience a glitch or a sudden rise in its speed of rotation. This glitch is called a starquake that causes a sudden change in the neutron star's crust.

This sudden increase could also deform the neutron star, changing its shape to an oblate spheroid, resulting in the generation of gravitational waves or gravitational radiation as the star spins. But the neutron star changes its shape back to spherical when it slows down, resulting in constant gravitational waves with a stable spin rate.

Like a glitch, a neutron star could also experience an anti-glitch, a sudden decrease in its rotational speed.

FAQs

How long do neutron stars last?

Neutron stars could last as long as 100,000 years to even up to 10 billion years.

What are neutron stars made of?

A neutron star is made of 95 % neutrons.

Are neutron stars hot?

Yes, the surface temperature of a neutron star is, on average, 600,000 K, which is more than 100 times hotter than the Sun.

Is a neutron star a black hole?

The mass of a neutron star is less than three solar masses. But if the mass exceeds three solar masses, the neutron star would end up as a black hole.

Why do neutron stars exist?

Neutron stars exist when a large star has neared its end, and its core is squeezed out. If the remaining core is between 1.4-2.16 solar masses, it forms a neutron star.