Q: What's a Megaparsec?
A: A million parsecs, of course.
Q: OK, so what's a parsec?
A: A madeup word ("parallax" + "arcsecond")
and a geometrical measurement of distance
commonly used by astronomers
distance (in parsecs) =
1/p (in arcseconds)
1 arcsecond = 1/3600 degree = 1/206265 radian
1 parsec = 3.26 light years
closest stars are a few parsecs away
closest large galaxy (Andromeda)
is about 0.75 Mpc away
Note: "p" is only measureable for relatively close
objects (currently this means d < 500 pc); "p" cannot be directly
measured for galaxies and other
methods of distance measurement must be employed.
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