Globular star clusters are a symmetrical collection of ancient stars (up to a million such stars). Recent estimates indicate that about 150 globulars exist in the Milky Way with only three being readily visible to the naked eye (the Andromeda Galaxy has been estimated to contain approximately 500 globular clusters). Since most of the globular clusters are more common in the southern hemisphere, scientists have deduced that our sun must lie away from the galactic core of the Milky Way. One of the most beautiful such globular clusters is M13 in Hercules.

Note: NGC 2419 in Lynx has the unusual distinction of being one of the most distant globular clusters in the Milky Way. At a distance of 300,000 light-years away and with a diameter of 260 light-years across, it is located near the edge of our galaxy and some did believe for a time that perhaps it was even an extragalactic globular cluster. Due to its great distance, the cluster has an apparent diameter of only 4.1' and is relatively dim at magnitude 10.39 (the brightest member star is only magnitude 17.3). This cluster was first observed by Herschel on the last day of 1788 and is considered the fourth brightest globular cluster in absolute magnitude and immediately after Omega Centauri, NGC 6388 in Scorpius and M54 in Sagittarius. A study by Harris et al (click here) suggests its age to be approximately 13 to 14 (+ 1) billion years old.

As with all globular clusters, NGC 2419 is best observed using narrow-field high-power views. The cluster lies between Gemini and Lynx and approximately half-way between Castor (α-Gem, mag 1.93) and 31 Lyn (mag 4.25). NGC 2419 is best observed during late winter and early spring when it is directly overhead after the end of astronomical twilight. In spite of its magnitude and distance, the cluster is visible in amateur equipment as a small blurry patch. Its classification reveals its very dense core.

Note: For an excellent article on globular clusters, see S&T (Mar/2006: 30-36).