Consider the following pairs :
Cepheids : Giant clouds of dust and gas in space
Nebulae : Stars which brighten and dim periodically
Pulsars : Neutron stars that are formed when massive stars run out of fuel and collapse
How many of the above pairs are correctly matched? (UPSC Prelims 2023)

Question

The correct answer is [A] Only one. Only Pair 3 is correctly matched.

Cepheids (Pair 1 – Incorrect): Cepheids (or Cepheid variables) are a specific type of star that brightens and dims periodically. Their period of luminosity is directly related to their absolute brightness, making them crucial \"standard candles\" for measuring distances in the universe. They are not clouds of dust.
Nebulae (Pair 2 – Incorrect): A Nebula is a giant cloud of dust and gas (mostly hydrogen and helium) in space. Some nebulae are regions where new stars are beginning to form (star nurseries), while others are produced by the explosion of a dying star, such as a supernova.
Pulsars (Pair 3 – Correct): Pulsars are highly magnetized, rapidly rotating neutron stars that emit beams of electromagnetic radiation out of their magnetic poles. They are formed when a massive star exhausts its fuel and undergoes a supernova collapse, leaving behind an incredibly dense core.

GKToday Admin · Accepted Answer

Only one The correct answer is [A] Only one. Only Pair 3 is correctly matched.

Cepheids (Pair 1 – Incorrect): Cepheids (or Cepheid variables) are a specific type of star that brightens and dims periodically. Their period of luminosity is directly related to their absolute brightness, making them crucial \"standard candles\" for measuring distances in the universe. They are not clouds of dust.
Nebulae (Pair 2 – Incorrect): A Nebula is a giant cloud of dust and gas (mostly hydrogen and helium) in space. Some nebulae are regions where new stars are beginning to form (star nurseries), while others are produced by the explosion of a dying star, such as a supernova.
Pulsars (Pair 3 – Correct): Pulsars are highly magnetized, rapidly rotating neutron stars that emit beams of electromagnetic radiation out of their magnetic poles. They are formed when a massive star exhausts its fuel and undergoes a supernova collapse, leaving behind an incredibly dense core.

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