A parsec (pc) is a measure of incredibly large astronomical distance.
The word comes from the phrase parallax second.
Parallax means the change in a star’s relative position in the sky when viewed from different places, and second refers to the smallest measurement of the change, stars move in arcs measured in seconds.
Imagine a clock with a sweeping second hand. Pretend that you are on Earth at the center of the clock looking up at a star at exactly 12:00.
Twenty-four hours later, you look up to see the star, but it appears to have moved to a position that is one second after 12:00.
In fact, it is Earth that moves along its orbital path; the star only appears to move.
What you see as a movement of one second, however, is actually a vast distance, but you are so far away from the star, the distance appears tiny.
One parsec equals 3.26 light-years, or the distance light travels in 3.26 years, approximately 19 trillion miles, or 30.4 trillion km.
Alpha Centauri, the star nearest the Sun, is about 1.3 parsecs away.
The first documented use of the term parsec was in 1913, and is attributed to Herbert Hall Turner.
Related Posts
-
Who Invented the Yard and How Did the Unit of Measurement Originate?
A yard is a unit of length in several different systems, and an international yard is equal to 3 feet, 36 inches, or 0.9144 metres. The word yard comes from the Old English…
-
What Is an Astronomical Unit and How Is the Astronomical Unit Used To Measure Distances In Space?
The astronomical unit (AU) measures the relatively short distances within our solar system. One AU is the mean distance from Earth to the Sun, about 93 million miles. We can say that Pluto's…
-
How Long is a Furlong, What Does it Mean, and How Did the Unit of Measurement Originate?
The furlong is an ancient British unit of measurement, literally meaning the length of a furrow. It's the distance a horse can pull a plow without resting, which was calculated at exactly 220…
-
How Far Is a League and Where Did the Unit of Measurement Come From?
Folk tales refer to a league as a specific distance. There were seven-league boots, and Jules Verne sent Captain Nemo twenty thousand leagues under the sea. A league is an ancient measurement. In…
-
How Long Is a Rod and Where Did the Unit of Measurement Come From?
The rod is still used as a unit of measurement for portaging in recreational canoeing, possibly because a rod is about the same length as a canoe. A rod was established to be…
-
Why Is the Hand Used As a Unit of Measurement to Measure the Height of a Horse?
For five thousand years, the height of a horse has been measured in hands. Body parts were our first points of reference for measurement. For example, a foot was exactly that, the length…
