The first thing I had to learn was how to see through a telescope. I will never forget the very first object I saw. It was the open cluster ‘Tuc 47’.
47 Tucanae or 47 Tuc is a spectacular globular cluster located in the southern constellation of Tucana. At magnitude +4.5, it appears to the naked eye as a slightly fuzzy star similar to the head of a tail-less comet. Always hidden from view for European and North American observers, 47 Tuc was discovered by French astronomer Nicolas Louis de Lacaille on September 14, 1751. Initially, Lacaille though he had found a comet until further inspection revealed its true nature.
47 Tuc is the second brightest globular in the sky, only Omega Centauri is more brilliant. It has an extremely dense core and is one of the most massive globular clusters surrounding the Milky Way. The cluster is located 2.5 degrees west of the Small Magellanic Cloud (SMC) and from most of the Southern Hemisphere, it’s circumpolar and never sets. In contrast from latitudes of 18N or greater, the globular can never be seen as it fails to rise above the horizon.
Through 7×50 or 10×50 binoculars, 47 Tuc appears as a bright starlight nucleus surrounding by a halo of soft pearly light. It’s clearly non-stellar in nature. Telescopically the cluster is stunning and a showpiece object of the night sky. In total it spans 31 arc minutes of apparent sky, almost exactly the same diameter as the full Moon.
A small 100mm (4-inch) scope reveals a bright compact core surrounded by a large 15 arc minute sphere with the brightest members resolvable. Even though small telescopes it’s a superb sight. A 200mm (8-inch) instrumet shows a swarm of stars in a glittering 3D view. The dense center remains unresolvable in stark contrast to the less dense outer regions. Overall it’s a breathtaking object for all sizes and types of telescopes.
47 Tuc is located 16,700 light-years from Earth and contains at least 500,000 stars. These include exotic stars with at least 23 blue stragglers and 23-millisecond pulsars known. The globular is estimated to be 13.1 billion years old.
