What Are Neutron Stars?

Neutron Stars

Neutron stars are too small to burn in comparison to the size and scale of our universe. A typical neutron star is about 20 kilometres in diameter. Since this type of star is a not very large type of star. However, despite its small size, its geological factors such as mass, density, etc. are potent. A neutron star has about 1.4 times the mass of our Sun. But isn’t it amazing that so much mass is packed into such a small space? The Himalayan Mountain range, where the world’s highest mountain is located, can be seen in these stars as a kind of mass accumulation trapped in a teacup. But how is this created? To find the answer to this problem, it is crucial to study the death of a star.

The Death Of A Star

A star’s main event is nuclear fusion. That is, the Hydrogen contained in the stars turns into Helium. The star burns up due to the excessive heat released there. This process also occurs in our Solar System’s nearest star, the Sun. In addition, due to gravity from the mass of a star, the hot plasma produced by fusion is attracted to the star’s core. This gravitational force and the force from the thermal energy released by nuclear fusion are equal and opposite, so the star remains stable.

The life cycle of a star
Image 1: The life cycle of a star

However, after the burning of Hydrogen, the star’s Hydrogen is depleted. Since the star doesn’t have enough mass to add more elements, Oxygen and Carbon remain in its core. At the end of this process, the star becomes a Red Giant. If this were compared to our Sun, the Sun would expand to the Earth’s orbit. That is, with the end of the Sun, the Earth will also be destroyed. After the Red Giant event, the star becomes a cloud of dust. These are known as Planetary Nebulae. Oxygen and Carbon in the remaining core are released into the universe. The star then becomes a white dwarf star.

The Birth Of A Neutron Star

Although the above process of death of a star is correct for the Sun, the situation is different for more massive stars. Because the mass of a star is very large. Oxygen and Carbon do not stop producing them. They are formed into Neon, Magnesium, Silicon, Bismuth, and Iron. In this way, an Iron core is finally created. If this is considered a large star, this Iron core is the size of our Earth. In this case, the electrons and protons in the nucleus of the atom fuse into neutrons. Finally, a core of atomic nuclei is formed. At this point, the star’s core continues to contract. It is happening at a very high speed. A speed of about 75000 km. Then, due to the collision of iron in the core, a huge explosion occurs. A supernova is that explosion.

SN 1994D (bright spot on the lower left), a type Ia supernova within its host galaxy, NGC 4526
Image 2: SN 1994D (bright spot on the lower left), a type Ia supernova within its host galaxy, NGC 4526
The star that ends here becomes a neutron star.
Image 3: The star that ends here becomes a neutron star.

Then the star becomes a star with a diameter of 20 km. The star is very dense. The temperature of a neutron star formed in this way exceeds one million degrees Celsius. Sometimes these stars rotate in pairs. Then an explosion occurs due to their collision. It is known as the Kilonova explosion.

Producing gravitational waves and resulting in a Kilonova
Image 4: Producing gravitational waves and resulting in a Kilonova

Such explosions can also be caused by black holes and neutron stars colliding. There, elements like gold and Uranium are created in space due to the heat released into the space and certain materials.

Types Of Neutron Stars

Neutron stars spin at extremely high speeds, producing intense radiation such as X-rays as well as extreme magnetic field pulsations. Because these are magnetically rotating. Most neutron stars are pulsars. A rotating neutron star. The first pulsations were observed using radio waves 50 years ago on August 6, 1967, but since then we’ve studied them in almost every wavelength of light, including X-rays and Gamma rays.

Artist concept of ancient pulsar J0108.
Image 5: Artist concept of ancient pulsar J0108. Image credit: X-ray: NASA/CXC/Penn State/G.Pavlov et al. Optical: ESO/VLT/UCL/R.Mignani et al. Illustration: CXC/M. Weiss

The other type is the magnetar star type. It has a magnetic field strength about a trillion times that of a normal neutron star. In May 2021, NASA reported that the Hubble Space Telescope had detected four FRBs (Fast Radio Burst) in the spiral arms of distant galaxies. These are thought to originate from magnets.

A magnetar is a type of neutron star, believed to possess an extremely powerful magnetic field and to be a candidate for causing many fast radio bursts
Image 6: A magnetar is a type of neutron star, believed to possess an extremely powerful magnetic field and to be a candidate for causing many fast radio bursts

According to all the points mentioned above, explosions such as a supernova or kilonova release heat and atoms into space and form various elements. They rotate again under gravity as a ring, forming the solar system of planets. We can conclude without doubt that our Solar System is also like that.


  1. NASA. 2022. Five Famous Pulsars from the Past 50 Years. [online] Available at: https://nasa.tumblr.com/post/163637443034/five-famous-pulsars-from-the-past-50-years#:~:text=Pulsars%20%E2%80%94%20rapidly%20spinning%20stellar%20corpses,X%2Drays%20and%20gamma%20rays
  2. EarthSky | Updates on your cosmos and world. 2022. EarthSky | What is a magnetar? [online] Available at: <https://earthsky.org/space/what-is-a-magnetar/>

Image Courtesies:

  1. Featured image: https://bit.ly/3zoMZa4
  2. Image 1: https://bit.ly/3Jmj2ff
  3. Image 2: https://go.nasa.gov/3Q6C2AC
  4. Image 3: https://bit.ly/3bgz4ed
  5. Image 4: https://bit.ly/3zOq2yy
  6. Image 5: https://go.nasa.gov/3oQ4gUt
  7. Image 6: https://bit.ly/3oHuMzs

Article by Sasanika Ruwanthi Jayarathna, 2nd Year Undergraduate, Faculty of Science, University of Colombo

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