UPSC Prelims 2023 Question:

Consider the following pairs

Sl. No.	Objects in Space		Description
1.	Cepheids	:	Giant clouds of dust and gas in space
2.	Nebulae	:	Stars which brighten and dim periodically
3.	Pulsars	:	Neutron stars that are formed when massive stars run out of fuel & collapse

How many of the above pairs are correctly matched?

Explanation:

• Cepheids, also called Cepheid Variables, are stars which brigthen and dim periodically. So, pair 1 is not correctly matched.
  
  

• A nebula is a giant cloud of dust and gas in space. Some nebulae (more than one nebula) come from the gas and dust thrown out by the explosion of a dying star, such as a supernova. Other nebulae are regions where new stars are beginning to form. So, pair 2 is not correctly matched.
  
  

• Neutron stars are formed when a massive star runs out of fuel and collapses. The very central region of the star – the core – collapses, crushing together every proton and electron into a neutron. Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. Pulsars have very strong magnetic fields which funnel jets of particles out along the two magnetic poles. These accelerated particles produce very powerful beams of light. So, pair 3 is correctly matched.
  
  

Therefore, option (1) is the correct answer. 

Subject: Science & Technology | Space and Related Developments