The First Sources of Light in the Universe

Galaxies - enormous collections of hundreds of billions of stars - are the basic assemblages of structure in the universe. A crucial question in modern astronomy is, How did these objects begin to form?

The Big Bang set the stage for the birth of stars and galaxies. Observations with ground-and space-based radio telescopes have now shown that the universe began almost entirely smooth, as a rapidly expanding hot sea of particles and intense light that followed the Big Bang. Within this sea rolled subtle waves. These gentle undulations in matter and energy density grew slowly but steadily under the influence of gravity. A few hundred thousand years after the Big Bang, the strength of these ripples was only one- thousandth of a percent above the smooth background. Although this process occurred long ago, even today light continues to stream in from this ancient time, and the primeval waves, destined to grow into great superclusters of galaxies, are clearly seen by our most sophisticated instruments. Over the hundreds of millions of years that followed, gravity continued its work until giant clouds of cooling gas, the forerunners of today’s galaxies, began to condense. Within these developed much smaller, denser clouds that gave birth to stars. The light from this first generation of stars, born some 12 to 13 billion years ago, brought the dawn of the modern universe with the birth of countless points of light that dot our night skies.

The Hubble Space Telescope has carried us back to within a few billion years of the Big Bang, allowing us to watch the growing up of young galaxies. But the actual birth of galaxies remains beyond our grasp. Within a billion years after the Big Bang, gravity had organized galaxy-sized clouds of gas, and stars condensed within these clouds and first ignited their nuclear furnaces. Looking back to that time is the primary goal of the Next Generation Space Telescope (NGST), the highest priority of the Astronomy and Astrophysics Survey Committee for the new decade. NGST will allow astronomers to peer into the distant past and see, for the first time, the birth of the modern universe.

Read More About The Next Generation Space Telescope (NGST)

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