What is a Neutron Star?
A neutron star is a stellar remnant–a super-compressed object left over when stars with a mass between 1.4 and about 3 times the mass of our Sun exhaust their nuclear fuel and collapse inwards. The result is a condensed sphere of matter about 20 km (12 miles) across, with a gravitational field approximately 2 x 10^11 times stronger than that of Earth’s. The density of a neutron star is so great that the protons and electrons making up the atoms fuse to form electrically neutral neutrons, the primary particles making up the neutron star. Because they are electrically neutral, such particles can be packed very closely together, resulting in a celestial object with similar density to that of the atomic nucleus. The neutron star is an exotic astronomical object whose existence was predicted by theory 35 years before one was actually discovered in 1968. The escape velocity for a neutron star is approximately half the speed of light. The tallest “mountains” on such a star measure in the mil
Neutron stars are very dense and spin very fast and are typically only 10-15 km in radius. Because neutron stars form from burnt-out stars, they do not glow. The collapse of the star causes the matter to be converted into mostly neutrons, and that explains the name neutron star. Some neutron stars emit radio waves that pulse on and off. These stars are called pulsars. Pulsars don’t really turn radio waves on and off–it just appears that way to people on Earth because the star is spinning. What happens is that the radio waves only escape from the North and South magnetic poles of the neutron star. If the spin axis is tilted with respect to the magnetic poles, the escaping radio waves sweep around like the light beam from a lighthouse. Far away on Earth, radio astronomers pick up the radio waves only when the beam sweeps across the Earth.
When a large star “dies,” it often explodes into a supernova. Afterwards, the remains of it are packed into a small space, measuring only a few miles in diameter. This is the neutron star, and it is named that because scientists think it is made mostly of neutrons. Neutrons, you might know, are part of the atom. The other parts are protons and electrons. Neutron stars can give off pulses of energy, so they are called pulsars. Some of this energy is the right frequency to be detected by a radio! It has to be a really strong radio, though. Thanks for writing! Click here for MORE SHORT QUESTIONS.
What does a supernova leave behind? That sort of depends upon the size of the original star. Remember, mass determines everything about the life of a star – so here’s another example of that rule. In the case of massive stars (those that die via the Type II supernova mechanism), there are two likely possibilities – a neutron star or a black hole. We’ll look at the less extreme case of the neutron star first.
