M3

M3 is one of the brightest globular clusters in the northern sky, a dense ball of about half a million stars some 34,000 light-years away.

It contains an unusually large number of variable stars, which astronomers have studied for over a century.

M3 was the first object Charles Messier discovered himself, in 1764. It is about 180 light-years across and more than 11 billion years old.

It is famous for holding more pulsating variable stars than any other globular cluster known, along with many blue stragglers, stars that look younger than their neighbors, possibly because of mergers or mass transfer.

M3 sits in a sparse area of sky, so it stands out well once you reach it.

Under dark skies, binoculars show M3 as a small, round glow; it is best on spring and early-summer evenings from mid-northern latitudes, when it rides high in the sky.