How the Stars Were Born

For the first time ever, scientists are taking an incredible journey to the dawn of the universe

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    Guessing how the very first stars formed is relatively easy, since the universe was so simple at the start of the Dark Ages. By the end, however, things were starting to get complicated. The stars had begun to affect their environment, and the environment in turn affected the stars in feedback loops that nobody has completely figured out. That's why astronomers want to test their theories with observation, and they will need a new generation of telescopes to do so.


    To spot the earliest objects, however, astronomers will have to stop looking for ordinary light. The universe has expanded vastly since its earliest days--but it isn't that galaxies and other objects are flying apart. Rather, it's that space itself has been stretching--a difficult concept even for a physicist to grasp, but which must be true according to the equations of relativity. Cosmologists say you should imagine the universe as a balloon with dots painted on its surface. As the balloon inflates, the dots will get farther apart--not because they're sliding around but because the balloon is stretching.

    That being the case, a light beam traveling through expanding space is stretched as well, its wavelength getting longer as it goes. Long-wavelength light is red; stretch it out longer and it becomes infrared light and then microwaves and, finally, long-wavelength radio waves. The flash that came from the Big Bang started out as visible light; by now, 13.7 billion years later, it's still streaming through space, but it has been stretched so much that astronomers have to use microwave antennas to detect it. The earliest galaxies came after the Big Bang, so their light isn't quite as old, hasn't been traveling as long and thus isn't stretched as much. That light should be detectable not as microwaves but as infrared--which is why the new telescopes will be fitted with infrared sensors. It's also why the James Webb telescope, NASA's planned successor to the Hubble, will be optimized to see infrared, not visible light.

    Still other telescopes will be trying to take pictures not of the first stars and galaxies, but of the clouds of hydrogen atoms they formed from and that they eventually destroyed. The hydrogen atoms emitted radiation too, in the form of radio waves, and several competing projects in various stages of completion in India, China, the Netherlands and Australia are being designed to see them. The last, known as the Mileura Widefield Array, is considered the most promising because its 500 separate antennas will be located on a remote cattle station in western Australia, far from any interference from earthly radio broadcasts. "The South Pole would be good too," says Jacqueline Hewitt, director of the Institute for Astrophysics and Space Research at M.I.T., which is a partner in the project, "but this is a bit more accessible. We'll need to cut some roads, though."

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