Our Place in the Galaxy

July 01, 2003

Imp1 copy

Provided by: Philippe Moussette
Summary authors & editors: Martin Ruzek; Philippe Moussette

Summer is a great time for observing the Milky Way, our home galaxy. Urban light pollution makes a view such as this difficult for many of us. The 5 minute exposure captured above through a 16 mm lens treats us to a detailed view of our galactic neighborhood, spiral arms and dust lanes. Actually, the view on a dark clear night far from city lights comes close to the above. The galactic plane of rotation is seen edge on in this view from Mont Cosmos observatory in Canada, from the galactic rim in the upper left towards the core of the Milky Way below the horizon in the lower right. Nearby Vega (only 25 light years distant) dominates the top center. But how does our galaxy relate to the Earth system? As we move through our solar neighborhood (we are approaching Vega at a rate of 19 km/sec), distant gravitational forces shift and may perturb comets from the Oort cloud to visit our solar system - some may impact Earth. The galactic core lies some 27,000 light years distant, and our solar system oscillates above and below the galactic plane by more than 50 light years with a frequency of 60-90 million years. On an even longer time scale, our solar system migrates through successive spiral arms over hundreds of millions of years as it revolves around the galactic center, increasing the chance of encounters with perturbing objects such as supernovae and large molecular clouds which may directly or indirectly impact life on Earth. Cosmic, isn't it? Just look up!

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