M4: The Closest Known Globular Cluster.

M4 is a globular cluster visible in dark skies about one degree west of the bright star Antares in the constellation Scorpius . M4 is perhaps the closest globular cluster at 7000 light years , meaning that we see M4 only as it was 7000 years ago, near the dawn of recorded human history . Although containing hundreds of thousands of stars and spanning over 50 light-years, M4 is one of the smallest and sparsest globular clusters known. A particularly unusual aspect for a globular cluster is M4 's central bar of stars. M4, pictured above , is one of the oldest objects for which astronomers can estimate age directly. Cluster white dwarfs appear to be at least nine billion years old - so ancient they limit the youth of our entire universe .