Neutron Stars – The Most Extreme Things that are not Black Holes

Summary

Neutron stars are the remnants of massive stars that have undergone supernova explosions. These ultra-dense objects, just a few kilometers wide but millions of times the mass of Earth, are made of tightly packed neutrons and exhibit extreme conditions, including intense gravity and temperatures reaching millions of degrees. The interior consists of exotic materials like 'nuclear pasta' and possibly quark-gluon plasma. Neutron stars also spin rapidly and emit radio pulses, with some interacting in violent collisions that produce heavy elements like gold and uranium. Their existence not only explains the life cycle of stars but also the creation of the elements essential for life and technology.

Takeaways

• 😀 Neutron stars are incredibly dense remnants of massive stars that have undergone supernova explosions, collapsing into objects only a few kilometers wide but millions of times more massive than Earth.
• 😀 The life cycle of a star involves a balance between gravity pulling inward and fusion pushing outward. When hydrogen runs out, stars with high mass undergo complex fusion processes, eventually creating iron which leads to their death.
• 😀 When a star’s core burns iron, fusion stops, and the core collapses under gravity. This creates a supernova explosion, which is incredibly powerful and can outshine entire galaxies.
• 😀 After the supernova, the remaining mass forms a neutron star, with gravity so strong it bends light around it. Neutron stars are incredibly hot, with surface temperatures reaching up to 1,000,000°C.
• 😀 Neutron stars have solid crusts made from iron and a dense core of nuclear matter. The matter within them is under extreme pressure, forming dense atomic structures, including ‘nuclear pasta’ which is incredibly strong.
• 😀 The inner core of a neutron star may contain a quark-gluon plasma, a state of matter that could turn protons and neutrons into quarks. This state is still not fully understood by scientists.
• 😀 Neutron stars spin at incredibly fast speeds, up to several times per second. Their strong magnetic fields produce beams of radio waves, making them visible as pulsars.
• 😀 Magnetars are neutron stars with extraordinarily strong magnetic fields, up to a quadrillion times stronger than Earth's magnetic field.
• 😀 When two neutron stars orbit each other, their orbits decay over time due to the emission of gravitational waves. This can lead to a kilonova explosion when they collide, forming heavy elements such as gold and platinum.
• 😀 Neutron stars are responsible for creating heavy elements in the universe, which are then scattered throughout space to eventually form new stars, planets, and even life. Our own solar system contains elements made by past neutron star collisions.

Q & A

What is a neutron star?

A neutron star is a remnant of a massive star that has exploded in a supernova. It is a dense, compact object, typically about 25 kilometers wide but with a mass around a million times that of Earth.

How do stars create energy?

Stars create energy through nuclear fusion, where the pressure from gravity forces nuclei to fuse, releasing energy that pushes against gravity. This balance between the outward pressure and inward gravitational pull keeps the star stable.

What happens when a star runs out of hydrogen?

When a star exhausts its hydrogen fuel, it begins to burn helium and other heavier elements in a process that eventually leads to the star’s collapse. For massive stars, this results in a supernova and the formation of a neutron star.

Why can't iron be fused in a star?

Iron cannot be fused because it is nuclear 'ash.' It doesn’t release energy when fused, and in fact, it requires energy to fuse, which causes the fusion process to stop, leading to the collapse of the star.

What is nuclear pasta, and why is it important?

Nuclear pasta is a form of matter inside a neutron star, where nuclei form long structures like spaghetti or lasagna. It is thought to be incredibly strong, potentially the strongest material in the universe, and contributes to the star's extreme density.

What is a supernova?

A supernova is a massive explosion that occurs when a star collapses under its own gravity, causing its outer layers to explode outwards while leaving behind a dense core, which may become a neutron star.

How do neutron stars emit pulses of radiation?

Neutron stars emit pulses of radiation due to their rapid spin and intense magnetic fields. As the star rotates, its magnetic field sends out beams of radio waves, which we detect as regular pulses.

What is the difference between a pulsar and a magnetar?

A pulsar is a neutron star that emits regular pulses of radiation, while a magnetar is a type of neutron star with an exceptionally strong magnetic field, sometimes quadrillion times stronger than Earth's.

What happens when two neutron stars collide?

When two neutron stars collide, they create a kilonova explosion, emitting massive amounts of energy and producing heavy elements like gold and platinum. This event is also a key source of gravitational waves.

How do neutron star collisions contribute to the creation of heavy elements?

Neutron star collisions create extreme conditions that allow the rapid production of heavy elements, such as gold and uranium, through a process where neutron-rich matter falls apart and reassembles in violent explosions.