Which units might astronomers use for measuring distances to objects like the Andromeda Galaxy?
Answer
Kiloparsecs or megaparsecs
The hierarchy of astronomical measurement units reflects the scale of the objects being studied. While the Astronomical Unit ($ ext{AU}$) works for the solar system and light-years/parsecs suffice for nearby stars and mapping the galaxy, these units become too small when dealing with extragalactic distances, such as measuring the separation to entire galaxies like Andromeda. To keep these enormous numerical values manageable for calculation and reporting, astronomers extend the parsec unit. They use kiloparsecs ($ ext{kpc}$), representing thousands of parsecs, or megaparsecs ($ ext{Mpc}$), representing millions of parsecs, to appropriately scale the measurements for the vast voids between galaxies.
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