NASA Telescope Picks Up Glow of Universe's First Objects
Using a telescope as a time machine, scientists at NASA’s Goddard Space Flight Center, Greenbelt, Md., are closer to identifying the first objects of the universe. Recent observations from the Spitzer Space Telescope strongly suggest that infrared light detected in a prior study comes from clusters of bright, monstrous objects more than 13 billion light-years away.
Image right: The right panel is an image from NASA's Spitzer Space Telescope of stars and galaxies in the Ursa Major constellation. The left panel is the same image after stars, galaxies and other sources were masked out. Image credit: NASA/JPL-Caltech/GSFC+ Full image and caption+ Timeline of the universe
Astronomers have gathered compelling evidence that everything – space, time, and matter – was created 13.7 billion years ago in a tremendous explosion called the Big Bang. What was left after all that fury, though, has been something of a letdown. Just a thin gas of mostly hydrogen and helium, all alone in the dark. Scientists want to know how all the interesting stuff – people, planets, and stars – came to be.
If you look at a sunset, you see the sun as it existed about eight minutes ago, because that's how long it took its light to cross the 93 million miles between the sun and Earth. We see the closest star system, Alpha Centauri, as it appeared about 4.5 years ago, and the closest large galaxy, Andromeda, as it existed around two million years ago. Look far enough, and you can see what ended the long night after the Big Bang -- the glow of the first brilliant objects to exist.
That's what researchers did with the Spitzer Space Telescope. They observed five areas of the sky for about 25 hours per region, patiently collecting light from even the faintest objects. Then they meticulously subtracted light from things that were in front of the remotest objects, like foreground galaxies and dust in our solar system or in interstellar clouds.
Image left: One still from an artist's animation that illustrates the universe's early years, from its explosive formation to its dark ages to its first stars and mini-galaxies. Image credit: NASA/JPL-Caltech+ Go to animation
"We are pushing our telescopes to the limit and are tantalizingly close to getting a clear picture of the very first collections of objects," said Alexander Kashlinsky of Goddard, lead author on two reports to appear in the Astrophysical Journal Letters. "Whatever these objects are, they are intrinsically incredibly bright and very different from anything in existence today."
Astronomers believe the objects are either the first stars - hundreds of times more massive than our sun - or voracious black holes that are consuming gas and spilling out tons of energy. If the objects are stars, then the observed clusters might be the first mini-galaxies containing a mass of less than about one million suns. Our own Milky Way galaxy holds the equivalent of approximately 100 billion suns and was probably created when mini-galaxies like these merged.
"There's ongoing debate about what the first objects were and how galaxies formed," said Harvey Moseley of Goddard, a co-author on the papers. "We are on the right track to figuring this out. We've now reached the hilltop and are looking down on the village below, trying to make sense of what's going on."
This study is a thorough follow-up to an initial observation presented in Nature in November 2005 by Kashlinsky and his team. "We used significantly longer (deeper) observations in different areas of the sky (four new locations in total). Longer observations allow us to remove still fainter foreground populations than in the earlier study and to better isolate the signal originating from faint and more distant populations," said Kashlinsky.
The new measurements also confirmed that the signal really came from remote objects and not just from the telescope itself, or the instrument. "In the new observations, we took a very sensitive picture of the sky, and then took another one of the same part of the sky with the telescope flipped upside down. This was done to see if any of the bumps on the sky seen in the previous observations arose from the telescope or instrument. If they did, the pattern should rotate when the telescope did. In fact, the sky looked the same independent of the orientation of the telescope. This confirms that the signals we saw actually arise from the sky," said Moseley.
With Spitzer, Kashlinsky's group studied the cosmic infrared background, a diffused light from this early epoch when the Big Bang leftovers first clumped into structures. Some of the light comes from an object so distant that, although it originated as ultraviolet and optical light, its wavelengths have been stretched to infrared wavelengths by the growing space-time that causes the universe's expansion. Other parts of the cosmic infrared background are from distant starlight absorbed by dust and re-emitted as infrared light.
"We know these objects lived within the first billion years after the Big Bang. From the strength of their infrared light signal, we can estimate the total amount of energy produced by these objects during that time. That total energy is so large, it must have been produced very efficiently. The only objects capable of doing this are either very large stars or black holes consuming lots of matter," said Kashlinsky.
The observations were made by Spitzer's infrared array camera, which was built by Goddard. Once the light was removed from the foreground, leaving only the most ancient light, scientists studied fluctuations in the intensity of infrared brightness. The fluctuations revealed a clustering of objects that produced the observed light pattern.
"Imagine trying to see fireworks at night from across a crowded city," said Kashlinsky. "If you could turn off the city lights, you might get a glimpse at the fireworks. We have shut down the lights of the universe to see the outlines of its first fireworks."
Observations of the cosmic microwave background by a co-author of the recent Spitzer studies, Dr. John Mather of Goddard, and his science team strongly support this theory. Mather is a co-winner of the 2006 Nobel Prize for Physics for this work. Another few hundred million years or so would pass before the first stars would form, ending the so-called dark age of the universe.
Mather, who is senior project scientist for NASA's future James Webb Space Telescope, said, "Spitzer has paved the way for the James Webb Space Telescope, which should be able to identify the nature of the clusters."
The Goddard team includes Kashlinsky, Moseley, Mather, and Dr. Rick Arendt.
For graphics and more information about Spitzer:
Additional media contact: Josh Chamot of National Science Foundation, 703-292-7730.
Goddard Space Flight Center