[meteorite-list] Constellations vs. asterisms

[Matson, Robert D.]

> I don't know the technical difference between "constellation" and
"asterism"
> except for one based on classical period constellations. I would
suppose
> that for people today the Big Dipper and Little Dipper are
constellations.

The reason the Big Dipper isn't a constellation is that it is only a
subset
of a constellation (Ursa Major). Similarly, the Great Square of Pegasus
is
an asterism. Going the other direction, the Summer Triangle is an
asterism
made up of three bright stars from three separate constellations. So
think
of asterisms as just easily recognizable star patterns. Constellations,
on
the other hand, are zones of the sky.  --Rob