Parsec is the Unit of Which Physical Quantity?

The correct answer for “Parsec is the unit of which physical quantity” is option B. Distance. In astrophysics and astronomy, a parsec is a widely used unit of distance. It is particularly significant for measuring vast distances between celestial objects in the universe. Now, let’s understand in detail why a parsec is crucial in the realm of astrophysics and is a unit of distance. 

Explanation:

What is a Parsec?

The term parsec stands for “parallax-second.” It is defined as the distance at which one astronomical unit (AU) subtends an angle of one arcsecond (1/3600th of a degree). In simpler terms, if an object’s parallax angle is one arcsecond when viewed from opposite sides of Earth’s orbit, its distance from Earth is one parsec.

Mathematically, 1 parsec ≈ 3.26 light-years or approximately 3.086 × 10¹³ kilometres.

Why is Parsec Used for Distance?

In astronomy, using kilometres or miles to measure the vast distances between stars, galaxies, or other celestial bodies becomes impractical. Instead, the parsec provides a more manageable way to express these immense distances, rooted in geometric principles derived from Earth’s orbital motion.

How Does Parallax Work?

To grasp the concept of a parsec, consider how parallax works:

As Earth orbits the Sun, nearby stars appear to shift slightly in position relative to distant background stars. This apparent shift, called stellar parallax, forms the basis of determining distances.
A star with a parallax angle of 1 arcsecond is said to be 1 parsec away.

The parsec is a unit of distance, not time, frequency, or angular acceleration. It plays a critical role in astronomy by helping scientists accurately measure and describe the universe’s vast expanse. Understanding this unit is essential for physics students exploring the mys