Magazine Article

The secrets of off-season globular

Witkoski, F Michael

2017

Overview

While the disk of the Milky Way is dense, dynamic, and rife with star formation, the halo is relatively calm. The X-ray radiation undoubtedly results from stellar material streaming from one star of a pair onto the superdense surface of its companion (be it a neutron star or a black hole), which no optical telescope will reveal. Because this slithering giant contains few bright stars for its size and little outstanding to the naked eye, observers often overlook it. While M87, the gravitational nucleus of the extensive Virgo Cluster, is one of the most thoroughly studied of its type, its total apparent brightness trumps the relatively unknown NGC 5634 by less than one magnitude. [...]that galaxy's thousands of globular clusters, visible as such only photographically, are much more celebrated than our lone globular at the opposite end of the constellation. Magnitude 9.2 NGC 5466 in Boötes is a diffuse globular with no immediate reference points, although the spectacular cluster M3 in the adjacent constellation Canes Venatici lies a cozy 5° west. While NGC 5466 is closer to the summer sky than M3, which is at the cusp of naked-eye visibility, I included it because it typifies the challenge of off-season globular clusters. Because globular clusters within the Milky Way total only about 150 objects, and because many are within the reach of portable telescopes, most observers could view more than half of them within a reasonable timespan.

• Publisher: Firecrown
• Subject: Astronomy / Black holes / Constellations / Globular clusters / Neutron stars / Observers / Star & galaxy formation / Star formation / Stars / Stars & galaxies / Telescopes / Virgo galactic cluster