Neutron stars are city-size stellar objects with a mass about 1.4 times that of the sun. Born from the explosive death of another, larger stars, these tiny objects pack quite a punch. Let's take a look at what they are, how they form, and how they vary.
When stars four to eight times as massive as the sun explode in a violent supernova, their outer layers can blow off in an often-spectacular display, leaving behind a small, dense core that continues to collapse. Gravity presses the material in on itself so tightly that protons and electrons combine to make neutrons, yielding the name "neutron star."
Neutron stars hold their mass inside a 20-kilometer (12.4 miles) diameter. They are so dense that a single teaspoon would weigh a billion tons, assuming that you somehow managed to snag a sample without being captured by the body's strong gravitational pull. On average, gravity on a neutron star is 2 billion times stronger than gravity on Earth. In fact, it's strong enough to significantly bend radiation from the star in a process known as gravitational lensing, allowing astronomers to see some of the back side of the star.
The power from the supernova that birthed it gives the star an extremely quick rotation, causing it to spin several times in a second. Neutron stars can spin as fast as 43,000 times per minute, gradually slowing over time.
Types of neutron stars
Some neutron stars have jets of materials streaming out of them at nearly the speed of light. As these beams pan past Earth, they flash like the bulb of a lighthouse. This pulsing appearance led them to be called pulsars.
When X-ray pulsars capture the material flowing from more massive companions, that material interacts with the magnetic field to produce high-powered beams that can be seen in the radio, optical, X-ray or gamma-ray spectrum. Because their main power source comes from the material from their companion, they are often called "accretion-powered pulsars." "Spin-powered pulsars" are driven by the stars rotation, as high-energy electrons interact with the pulsar's magnetic field above their poles. Young neutron stars before they cool can also produce pulses of X-rays when some parts are hotter than others.
As material within a pulsar accelerates within the magnetosphere of a pulsar, the neutron star produces gamma-ray emission. The transfer of energy in these gamma-ray pulsars slows the spin of the star.
Magnetars have magnetic fields a thousand times stronger than the average neutron star. The resulting drag causes the star to take longer to rotate.
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