A kiloparsec (kpc) is a unit of measurement used in astrophysics and astronomy to describe distances on cosmic scales. It is equal to one thousand parsecs. A parsec (pc) is a unit of length used in astronomy to express large distances, and it is approximately equal to 3.09 × 10^16 meters or 3.09 × 10^13 kilometers.
So, a kiloparsec is equivalent to:
1 kiloparsec (kpc) = 1,000 parsecs (pc)
Kiloparsecs are often used to describe distances within galaxies, particularly when discussing the size of a galaxy or the scale of its components. For example, the size of a galaxy's disk or the distance between star clusters within a galaxy might be expressed in kiloparsecs. Additionally, kiloparsecs are used to measure the separation between galaxies in galaxy clusters and superclusters. Since astronomical distances can be extremely large, the parsec and its multiples provide a convenient way to express these distances in a more manageable manner.
A chain is a unit of length used in some older systems of measurement, particularly in surveying and land measurement. In the United States, one chain is equal to 66 feet or 22 yards. Internationally, it's defined as exactly 20.1168 meters.
Chains were historically used for measuring large plots of land and for surveying purposes, often in agriculture and real estate. However, the use of the chain as a standard unit of measurement has largely been replaced by the more modern and standardized metric and imperial systems, which use units like meters, feet, and yards.
The term "chain" comes from the practice of physically measuring land using a chain made of linked metal bars or wire. Each chain was typically 66 feet long, and surveyors would lay out chains end to end to measure distances across large areas. Today, modern surveying equipment such as electronic distance measuring devices (EDMs) and GPS technology have largely replaced the use of physical chains in land surveying.