STAR STUFF: The formation of neutron and pulsar stars.
Stars come in many sizes. They start out being made of mostly Hydrogen. Later they start producing heavier atoms. The gravitational force at the center crushers the atoms together. The star’s temperature increases at the core until nuclear fusion begins. After that, helium fuses to form carbon, carbon fuses to form Nitrogen, and so on. Fusion releases more energy than it takes to start itself(up to the production of the iron atom). Pressure releases in these different fusion reactions get the star off-balance. The real star begins to collapse in its center. All the electrons and the nucleus start crushing together. Protons fuse with electrons to form neutrons, producing neutrinos and antineutrinos. This produces a tremendous amount of energy that causes a massive explosion. The size of the star determines the explosion’s strength. Either a nova, a supernova, or a hypernova is born. The heavier particles are scattered into space. The mass remaining is the most spherical and dense object in the universe. This star is made up of a thick substance of neutron, and we call this substance neutronium. This is how neutron stars are formed.
A pulsar is born. The neutron stars start spinning rapidly (1000 rotations per second). Some of the charged particles begin to produce a magnetic field. This magnetic field has a massive force on charge particles at the axis of the star’s magnetic field. These charged particles form a jet. The Sun is making helium out of Hydrogen right now; that’s how and why it shines. The supernova distributes these heavier elements into the interstellar environment. Most of the most extreme elements are created during neutron star collisions. Elements are formed by nuclear fusion in stars. Up to carbon for small stars like our Sun. Up to iron for more giant stars. No star can synthesize higher than Ni-56 and Co-56 (which decay back into Fe-56). This means nuclear processes can only make up iron. When iron is produced, it takes too much energy to go further, so the star collapses and explodes. The debris of supernovae forms solar systems, like ours, with natural elements up to uranium. The gold you own was made in a titanic collision of two neutron stars billions of years ago in an explosion.
The most common element in the universe is Hydrogen, making up 70% of the visible universe by mass. The second most common element in the universe is helium, making up 20% of the universe by mass. When stars formed, they acted as a gateway to heavier elements. Stars are nuclear furnaces. Stars are long-lived structures. After fusion, stars go into a slow-burn process—the Helium burning phase results in primarily carbon and oxygen cores. The Silicon burning phase produces the heaviest elements, iron, nickel, and zinc. These last two fusion reactions absorb energy, rapidly destabilizing the star and leading to its death. The death stages of these stars produce the remainder of the elements we observe today. Iron is the heaviest element that can be stably made in stellar nucleosynthesis. Neutron stars are the second most dense objects other than black holes. In any binary neutron star system, these stars revolve around each other at a colossal speed when they come together.
Dying stars seed the interstellar medium with heavier elements. A supernova is an enormous nuclear furnace producing much heavier elements of the heavier elements e. g., gold, silver, lead, mercury, and platinum. Gravity pulls the dust and debris together to form new stars, solar systems, and planets. This cycle of stellar nucleosynthesis produces new mass without end until the end is near. The CNO cycle refers to the Carbon-Nitrogen-Oxygen cycle, a process of stellar nucleosynthesis in which stars on the Main Sequence fuse hydrogen into helium via a six-stage sequence of reactions. Stellar nucleosynthesis involves nuclear reactions through which new atomic nuclei are synthesized from pre-existing nuclei or nucleons. Stars form heavy elements by starting with the smallest atom of Hydrogen.
Several billion years ago, a molecular cloud (or Nebula) of almost pure Hydrogen sat, relatively motionless in the area roughly aligned with where our Solar System is today. It contained insufficient gravitational mass to coalesce; it would have become a star system with some gaseous planets. No heavier elements existed within the Nebula to allow rocky, silicon, carbon, and iron planets to form. Several light years away existed a super-massive star. It lived a few million years. Because it was a supergiant, it burned through its fuel at a hyper-rapid pace. When it exploded, our solar system was born.
To fuse Hydrogen into helium, you need to convert half of the protons into neutrons via the weak interaction, which is very weak. The problem is that two protons can be held together very briefly (less than a femtosecond), which is too short for either proton to undergo beta decay. The two protons will bounce back unless the beta decay happens immediately after the collision. As a result, a proton in the Sun’s core must wait 9 billion years to fuse with another proton into deuterium. More massive stars resort to a more efficient process known as the CNO cycle.
