Consider the following pairs:Objects in space — DescriptionCepheids : Giant clouds of dust and gas i

Q: What is UPSC Prelims?

UPSC Prelims is a competitive examination conducted in India. This question is from the 2023 UPSC Prelims Science & Technology paper.

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Question

Consider the following pairs:Objects in space — DescriptionCepheids : Giant clouds of dust and gas in spaceNebulae : Stars which brighten and dim periodicallyPulsars : Neutron stars that are formed when massive stars run out of fuel and collapseHow many of the above pairs are correctly matched?

Accepted Answer

Correct Answer: A — Only oneStep-by-step Solution:Pair 1 — Cepheids: Giant clouds of dust and gas: This is incorrectly matched. Cepheids (also called Cepheid Variables) are a type of pulsating star that brighten and dim periodically with very regular intervals. Their period-luminosity relationship (discovered by Henrietta Swan Leavitt) makes them invaluable as 'cosmic yardsticks' for measuring astronomical distances up to tens of millions of light-years. They are NOT clouds of gas and dust. ✗Pair 2 — Nebulae: Stars which brighten and dim periodically: This is incorrectly matched. A Nebula is a giant cloud of dust and gas in space. Some nebulae are remnants of exploded stars (like the Crab Nebula from a supernova). Others are regions of active star formation (like the Orion Nebula) — these are sometimes called 'stellar nurseries.' They are NOT stars that brighten and dim. ✗Pair 3 — Pulsars: Neutron stars formed when massive stars collapse: This is correctly matched. Pulsars are rotating neutron stars that emit beams of electromagnetic radiation from their magnetic poles. As they rotate, these beams sweep across space like a lighthouse, creating pulses of radiation detectable from Earth at very regular intervals (ranging from milliseconds to seconds). Neutron stars are indeed formed when massive stars (more than about 8 solar masses) exhaust their nuclear fuel and undergo a core-collapse supernova explosion. ✓Why other options are incorrect:Option B (Only two): Incorrect — only pair 3 is correctly matched.Option C (All three): Incorrect — pairs 1 and 2 are swapped.Option D (None): Incorrect — pair 3 is correctly matched.Key Concept: Cepheids → variable stars (period-luminosity relation used for cosmic distance measurement); Nebulae → interstellar clouds of gas and dust (either star-forming regions or supernova remnants); Pulsars → rotating neutron stars (extreme density, emit radio waves or X-rays). Magnetars are a special type of neutron star with extremely powerful magnetic fields.

Consider the following pairs:Objects in space — DescriptionCepheids : Giant clouds of dust and gas in spaceNebulae : Stars which brighten and dim periodicallyPulsars : Neutron stars that are formed when massive stars run out of fuel and collapseHow many of the above pairs are correctly matched?

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Consider the following pairs:Objects in space — DescriptionCepheids : Giant clouds of dust and gas in spaceNebulae : Stars which brighten and dim periodicallyPulsars : Neutron stars that are formed when massive stars run out of fuel and collapseHow many of the above pairs are correctly matched?

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More Questions from Space Technology – ISRO Missions, Satellites & Exploration

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