The generously illustrated The Guide to the Galaxy by Nigel Henbest and Heather Couper (Cambridge University Press, 1994) is an anatomy of our galaxy, showing the spatial relationships and significance of its parts. There is still much to discover, much to debate, but at last we have a description in plain English. Only in the last few years have the various strands of evidence been multiplied and then reconciled one with the other to give us a reasonable model of the Milky Way galaxy. For the stars, clusters and bright and dark nebulae there has been no easily comprehensible account of galactic geography (glactography?) which would enable us to “see” them in three dimensions. Indeed, the Moon, planets and satellites appear nearer only because they move across the background. Seeing depth in the night sky is optically impossible, for whether by eye or telescope the objects beyond the solar system simply appear to be at the same very large distance from us, as if they were pasted on the surface of the celestial sphere. Although we have known directions and distances of various objects, and the “poached egg” picture of the galaxy has been developed to show both the spiral structure of the disc and the arrangement of the objects within, it has been difficult tc relate all this information to the night sky as we view it. Moreover, while our understanding of many elements of the solar system has improved-details of the solar wind, the interplanetary medium and the arrangement of galaxies-our knowledge of the geography of our own galaxy has remained fragmentary. Such has been the torrent of new information, concepts and theories that even the well-informed have had trouble piecing it all together. Many are new discoveries: pulsars and quasars, for instance, which required a great deal of research before we began to understand them. Some are objects, such as black holes, previously merely suspected to exist. Some are old friends reclassified: types of variable star, for example, which seem to have bred like rabbits. Advances in the physical sciences have meant that we now recognise a whole host of celestial phenomena which, even 40 years ago, when Fred Hoyle’s popular Frontiers of Astronomy was published, were unknown or poorly understood. For the astronomy buff, recent decades have been a time of unprecedented and, at the same time, baffling discovery.
0 Comments
Leave a Reply. |