A parallax is when a foreground object moves compared to a more distant background. For the vast gulfs between galaxies, astronomers use kiloparsecs, megaparsecs and even gigaparsecs (feel small yet?).Ī parsec is defined as: "the distance corresponding to a parallax of one arcsecond." While that might read like absolute gibberish, there is a rational explanation. Yet, for the distance between stars outside of our solar system, a larger unit is necessary.
In our solar system, kilometers or astronomical units tend to get the job done in measuring distance in space. While it might not seem like a lot, it might help to put it in perspective: it would take photons of light three years to travel one parsec's distance. Photo credit: Pinterest.Īlso equivalent to 3.26 light-years, a parsec is a nearly unimaginable distance packaged in palatable terms. One parsec is equal to about 31 trillion kilometers, and most of the stars visible to the unaided eye in the night sky are within 500 parsecs of our sun. Parsecs measure extremely long distances to astronomical objects outside of our solar system.
In astronomy, which of the following units of measurement is the longest?Ĭonsidering gigametre, light-year, parsec and lunar distance, the answer is: parsec.Ĭontrary to what Han Solo says in Star Wars, a parsec is a distance, not a unit of time.
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