May 11th Public Lecture: Globular Clusters and Star Birth
By Lisa Marie Browne, Centre for Astronomy, NUI Galway
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centres. The name of this category of star cluster is derived from the Latin globulus—a small sphere. A globular cluster is sometimes known more simply as a globular.
Globular clusters, which are found in the halo of a galaxy, contain considerably more stars and are much older than the less dense galactic or open clusters, which are found in the disk. Globular clusters are fairly common; there are about 158 currently known globular clusters in the Milky Way, with perhaps 10 to 20 more still undiscovered. Large galaxies can have more: Andromeda, for instance, may have as many as 500. Some giant elliptical galaxies, particularly those at the centres of galaxy clusters, such as the biggest of the Virgo Galaxies; M87, may have as many as 13,000 globular clusters. These globular clusters orbit the galaxy at large radii of 40 kiloparsecs (approximately 131,000 light-years) or more.
Although it appears that globular clusters contain some of the first stars to be produced in the galaxy, their origins and their role in galactic evolution are still unclear. Their formed when a giant molecular cloud collapses; its stars have identical compositions and were formed within a short period of time. Multiple generations of stars exist in all globular clusters, with no two clusters having the same multiple generation pattern. This is revealed in their colour-magnitude (temperature-brightness) diagrams and in the chemical properties of the stars and it was recently voted as one of the Hubble Space Telescopes top discoveries. This talk by Lisa Marie Brown from the Centre for Astronomy at NUI Galway will cover the main topics of globular clusters and the different objects that have been found to date.
See you at the Westwood House Hotel for this talk at starting 7.30pm and join us for a chat with Tea & Coffee afterwards.
Spectacular April Aurora
A very strong and vivid display of the Aurora surprised Irish sky watchers on evening of April 17th with a spectacular display of the northern lights. Unlike the aurora a month earlier on St Patricks Day that was the strongest such storm of the current 11year solar cycle, This display was over within two hours but was a beautiful explosion of colour as you can see in the movie HERE by Steve Hanley at Lough Talt in the Ox mountains that straddle south Co Sligo, photo above by Ronan Newman, Chairperson of the Galway Astronomy Club at Knock Airport.