Explanation:
Gathered
at the center of this sharp skyview are the stars of
Messier 67,
one of the oldest known
open star clusters.
In fact, though open star clusters are usually much younger, the
stars of M67
are likely around 4 billion years old, about
the same age and with about the same elemental abundances as
the Sun.
Open clusters are almost always
younger because they are dispersed
over time as they encounter other stars,
interstellar clouds, and experience gravitational tides while
orbiting
the center of our galaxy.
Still, M67 contains over 500 stars or so and lies some
2,800 light-years away in the
constellation
Cancer.
At that estimated distance, M67 would be about 12 light-years across.
