In astronomy, pulsars are:

A pulsar is a highly magnetised, rapidly spinning neutron star that sends out beams of radiation from its magnetic poles. As it rotates, these beams sweep across space like the beam of a lighthouse, and we detect them as regular pulses.

What a neutron star is:

• When a massive star, roughly 8 to 25 times the Sun's mass, runs out of fuel, its core collapses and the star explodes as a supernova.
• The collapsed core becomes a neutron star, an extremely dense object made mostly of neutrons.
• It has more mass than the Sun but a diameter of only about 20 km.
• A teaspoon of neutron-star material would weigh about a billion tonnes on the Earth.

Why pulsars spin so fast:

• When the core collapses, it keeps its angular momentum, so it spins much faster, just as a figure skater spins faster by pulling in her arms.
• Some pulsars rotate hundreds of times per second; these are called millisecond pulsars.

Discovery:

The first pulsar was discovered in 1967 by Jocelyn Bell Burnell, a postgraduate student at Cambridge, with her supervisor Antony Hewish.

Antony Hewish shared the Nobel Prize in Physics in 1974 for the discovery. Bell Burnell was not included, which was widely criticised.

Famous pulsar:

The Crab Pulsar lies at the centre of the Crab Nebula, the remains of a supernova recorded in 1054 CE.

Uses of pulsars:

• Their pulses are so regular that they act like very precise cosmic clocks.
• A binary pulsar discovered in 1974 provided indirect evidence of gravitational waves; its discoverers, Hulse and Taylor, won the 1993 Nobel Prize.

Indian contribution:

The Giant Metrewave Radio Telescope (GMRT) near Pune, India, has discovered many pulsars and is part of international efforts to detect gravitational waves using pulsar timing.

Why not the other options?

• ✗Young stars still forming are called protostars.
• ✗Pulsars are not exploding galaxies.
• ✗Giant clouds of gas are nebulae.