When NASA's infrared Spitzer Space Telescope snapped pictures of a distant quasar in the Draco constellation in October 2003, the photo shoot was only intended to calibrate the instrument. Those images, however, just may have provided a glimpse of the very first stars in the universe.
"We think we are seeing the collective light from millions of the first objects to form in the universe," explains Alexander Kashlinsky of the NASA Goddard Space Flight Center, who details the finding in the current issue of Nature. "The objects disappeared eons ago, yet their light is still traveling across the universe."
Scientists have theorized that the first stars appeared as early as 100 million years after the big bang, which occurred 13.7 billion years ago. Prior to that point, the universe lacked light and was a featureless space filled with hydrogen and helium. Clumps of these elements eventually coalesced into stars, nascent galaxies and ultimately formed the brilliant universe of today.
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According to the researchers, the light from the earliest stars is still detectable amidst the infrared light that makes up the background of the observable universe. Although this light was initially high energy, ultraviolet light, it has shifted to lower and lower energies and wavelengths over time as the universe has expanded, the so-called redshift. By subtracting out light from the camera itself, along with that from our solar system, interstellar gas and dust, and, finally, the estimated light from all the stars, galaxies and other light sources from the last 13 billion years or so, the team isolated what it believes is the dawn of light.
"We removed everything we knew--all the stars and galaxies both near and far," says co-author John Mather, also at Goddard. "We were left with a picture of a part of the sky with no stars or galaxies, but it still had this infrared glow with giant blobs that we think could be the glow from the very first stars." (In the image above, the top half shows a section of space in Draco and the bottom half shows the same section once all stars, galaxies and other light sources have been removed. The remaining yellow and orange glow is believed to come from the first stars.)
Subsequent observations, such as those planned for the James Webb Space Telescope, scheduled to launch in 2013, may tell a different story. But the team is confident that these images reveal the earliest stars because the picture remains the same over the four different infrared wavelengths observed.
"It took us over a year to convince ourselves that we did [the calculations] well," Kashlinsky notes. "But we found the same signal at all wavelengths."
