Arcing across the night sky is a pale band of light the Romans called the via lactea — the Milky Way. Astronomers have known since the 1920s that this band is an edge-on view of the Galaxy in which we live: a vast pinwheel teeming with nebulae, gas clouds and billions upon billions of stars. For most of the nine decades since, astronomers also thought that our Galaxy and others like it were rather quiet places: ponderous, slowly rotating structures that formed many eons ago and had settled into uneventful middle age.
But then they began to see the Milky Way with fresh eyes (see ‘Galactic portrait’). Starting in the 1970s and 1980s, new generations of ground- and space-based telescopes began mapping the Milky Way at wavelengths ranging from microwaves to X-rays, revealing an unimagined richness. By the 2000s, syste-matic observing programmes were tracing galactic structures that sprawl across most of the heavens, and are so big that no one had noticed them before. By the present decade, teams of astronomers were racing to build ever-more powerful computer simulations to model the origins of galaxies on every scale from cosmos to star clusters. And by next year, the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile will be mapping the Galaxy at unprecedented levels of detail.
Astronomers are still struggling to assimilate all this new information. Disagreements, uncertainties and unanswered questions abound. But no one today would argue that our cosmic home town is a quiet backwater. The emerging picture of the Milky Way reveals that the Galaxy was born in chaos and shaped by violence, that it lives in a state of turbulent complexity, and that its future holds certain catastrophe.
To read more, click here.