Parallax, as we just mentioned, is describing the apparent motion of a star. Arcseconds are frequently abbreviated as “arcsec”, so parallax-arcsec got shortened into parsec. The actual term “parsec” has a somewhat fun origin - it’s actually a mashup of the words “parallax” (the apparent motion of the stars) and “arcsecond” (how far they move). Unlike the light year, which is based in the physics of light, a parsec was determined geometrically using the size of the orbit of the Earth around the sun, and the apparent motion of nearby stars. The distance from us to the center of our galaxy is measured in tens of thousands of light years. A light year, as we’ve talked about before, is quite a long distance, but once you get away from the immediate group of stars surrounding our solar system, it’s less useful as a ruler, since everything is so far away. The parsec (regardless of what you remember from Star Wars’ infamous line re: the Kessel Run) is a unit of distance that’s equivalent to 3.26 light years. In this case, the base unit is a parsec, instead of a gram or a meter.
WHATS A PARSEC FREE
If that was not your question, please feel free to ask again!) Kiloparsecs are another unit used to measure huge distances between objects in space, and if the ‘kilo’ part seems familiar from having seen words like kilogram and kilometer, you’d be exactly right - the prefix here just means 1000 of the part that follows. (Note: I am assuming this submission means “What is a kiloparsec, and what do we use it for?”.
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