MCQ Detailed View

A parsec is a unit of distance used in astronomy to measure vast stretches between celestial objects such as stars and galaxies. The term "parsec" stands for "parallax of one arcsecond" and is based on the principle of stellar parallax, which measures how the position of a star appears to shift relative to distant background stars when observed from two different points in Earth’s orbit around the Sun. Definition:

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  1 parsec ≈ 3.26 light-years, or about 3.09 × 10¹³ kilometers (3.09 trillion km).

  
  


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  It is the distance at which one astronomical unit (the average distance between Earth and the Sun) subtends an angle of one arcsecond.

  
  

✅ Why Astronomers Use Parsec:

Distances in space are so immense that kilometers or miles become impractical. Instead, astronomers use:

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  Astronomical Unit (AU): Distance within our solar system.

  
  


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  Light-year: Distance light travels in one year.

  
  


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  Parsec: A larger unit mainly used to measure distances between stars and galaxies.

  
  

✅ How It Works:

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  Imagine observing a nearby star from Earth in January and again six months later in July, when Earth has moved to the opposite side of its orbit.

  
  


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  The star appears to shift slightly against the background of more distant stars.

  
  


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  If the observed shift equals one arcsecond, the star is defined as one parsec away.

  
  

❌ Incorrect Options:

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  Energy, Time, Power: These are physical quantities unrelated to measuring astronomical distances.

  
  

✅ Final Answer:

A parsec is a unit of distance, commonly used in space science and astronomy to measure the enormous separations between stars and galaxies.