Our cosmos is full of amazing things and contains never ending possibilities. Sometimes these possibilities challenge the general physics laws or sometimes they need more developed science to study them deeply. Cosmos may surprise us with it’s possibilities but it also give us an opportunity to make our current physics more developed and allows us to study the cosmos like never before.
Neutron stars is one of those astonishing objects in our cosmos which sometimes challenges the basic sciences or it sometimes inspire us to develop our current sciences. The properties of neutron stars are utterly out of this world-a single teaspoon of neutron star material would weigh a billion tons. If you were to somehow stand on their surface without dying, you’d experience a force of gravity 2 billion times stronger than what you feel on Earth.
Neutron star is created when a massive star dies by a supernova explosion, and its core collapses.When an old star dies, its core runs out of nuclear fuel to produce heat and pressure. It’s the pressure that keeps the core from collapsing under its own weight. The gravity of large stars is so strong that the atoms of the core can’t fight against it. For stars like our Sun, the core collapses so tightly that electrons of the atoms reach a peak pressure. The star reaches a stable state known as a white dwarf, where the pressure of the electrons balances the gravitational pressure of the star’s mass.But a white dwarf is only stable up to a mass of 1.4 Suns, known as the Chandrasekhar limit. If an old star’s core is more massive than that, the electron pressure isn’t strong enough to counter gravity. The electrons are squeezed into the protons of the atoms, turning them into neutrons. The star collapses to the point that the pressure of neutrons counters gravity. This is known as a neutron star. Neutron star have very intense gravitational field due to it’s extreme mass and having escape velocity of 0.4 times the speed of light. There’s also a limit for a mass of neutron star and that limit is termed as Tolman-oppenheimer-volkoff limit. The estimated calculations for TOV limit put it somewhere between 1 to 2.16 solar masses. However some recently discovered neutron stars shows exception in their masses.
Types of Neutron Stars
Pulsars are rapidly spinning neutron star, extremely dense star that appear to emit short pulses of radio radiation with periods between 1.4ms and 8.5ms.It is composed almost entirely of neutrons and having a diameter of only 20 km (12 miles) or less. So how do they spin so fast? Well the answer lies in a basic law of physics. We all know if an ice skater tucks in her arms as she twirls, her spin will also speed up likewise when when you squash a big spinning star, it’s spin speeds up.
Most of the pulsars spin at a rate of about once per second but the fastest pulsars can rotate at up to ~650 times a second. If anything is spinning faster than around 50 millisecond is generally referred to as millisecond pulsars.
Magnetars is also a type of neutron stars that carries extremely high magnetic field. It have ~ 1015 gauss of magnetic field which is thousand trillion times stronger than the earth’s , and between 100 and 1000 times stronger than that of a radio pulsars, making it the most magnetic objects known. The idea of a magnetars was first introduced in 1987 and it is used to successfully explain the soft gamma repeaters in 1992. But it was taken seriously when the detection pulsation and the measurement of the spin down rate of Soft gamma repeaters suggested that it was a neutron star with a magnetic field strength of 8×1014 gauss.
By:- Akash Sharma