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Image by Jeremy Perkins

Pulsars: The Lighthouses of Space


What are pulsars?


How do they work?

Pulsars are part of a group of objects known as neutron stars that form after a star has run out of fuel and collapsed in on itself following a supernova, or the explosion of a star.


Pulsars rotate extraordinarily fast, anywhere from once every second to hundreds of times per second. They are also very small, about the size of a city (about 12.4 to 14.9 miles in diameter), but they are also very dense, many being more than 2 times the mass of the sun, with an extremely strong gravitational pull.


Types of Pulsars?

Millisecond pulsars exist with the help of a companion star, whose material can be fed into the pulsar, causing it to spin faster and faster. If a millisecond pulsar is found alone, it is likely because the companion star has been destroyed by the pulsar. There are also canonical pulsars which spin slightly slower than millisecond pulsars.

Pulsars can be powered through 3 methods:

  • Rotation: Powered by energy of a rotating star

  • Accretion: Gravitational potential energy of matter drawn into the pulsar powers it

  • Magnetar: Magnetic field decay of very strong magnetic field provides power

Some unusual pulsars:

  • Vela Pulsar is the brightest known radio pulsar

  • PSR J0901-4046 spins once every 75.9 seconds, longest pulsar

  • PSR J1841−0500 did not spin for 580 days

  • PSR B1931+24 spins for a week then stops for a month.

Pulsar planets have also been found around the PSR B1257+12 millisecond pulsar. These were some of the first discovered exoplanets. The planets were likely formed from two white dwarfs merging, forming a pulsar.

The "flash" astronomers observe from a pulsar comes from beams of radiation opposite each other. As the pulsar spins very fast, the beams of radiation appear to blink like the light from a lighthouse. And much like a lighthouse, each pulsar spins at a slightly different rate, giving it a unique flash characteristic much like that of a lighthouse. 

The high density of the pulsars explains their high spin rate. Stars already rotate, but bringing more mass closer to the center of mass will drastically increase the spin rate. If the pulsar became even denser, the event horizon, the point at which all matter, even light, cannot escape, eclipses the surface of the pulsar, and a black hole is formed.


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