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11 MAR 2004 |
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1. Message from ancient universe 2. Old photos of young galaxies
On Mar. 1, French and Swiss scientists announced the discovery of the most distant object ever located, at a distance of (yow!) 13.23 billion light years. The galaxy is seen when the universe was about 470 million years young, barely 3 percent of its current age. (Top left): A near-infrared image of Abell 1835 IR1916 (circle in the square), behind a galaxy cluster. Top right: Detail of the ancient galaxy, still in the white circle. Bottom: The detail region, seen in visible and infrared light. The galaxy is invisible in visible light, but visible in infrared radiation (especially the H-band) indicating a huge red-shift. This puff of photons came from the most distant object ever seen. Photos: European Southern Observatory
Two weeks ago, this galaxy (outlined in white) was the furthest object on record, imaged when the universe was just 750 million years old. The old gal is behind a cluster of galaxies called Abell 2218, and appears several times due to the focusing of the gravitational lens in Abell 2218. Photo: J.P. Kneib and Richard Ellis, Advanced Camera for Surveys, Hubble Space Telescope
Looking long and hard into one of the darkest parts of the sky, the Hubble telescope made this image of 10,000 galaxies, in this 13-day exposure. About 100 small, red galaxies may date to 800 million years after the Big Bang. The nearest galaxies -- the larger, brighter, well-defined spirals and ellipticals -- thrived about 1 billion years ago, when the cosmos was 13 billion years old. Photo: NASA
If you're looking for the stuff of the universe, you better be prepared to deal with invisible and unbelievable stuff. Dark energy matters more than dark matter. |
 Geezer galaxies found?
Scientists have just released photos of two astonishingly distant galaxies that burned in the first billion years of the universe. The ancient light traveled more than 13 billion light years, was focused by a gazillion-ton lens, and finally was scooped up in monster telescopes in Chile, and Hawaii. Based on how the starlight was stretched by the Doppler effect, these galaxies must have been cooking within a few hundred million years of the Big Bang. (Background blip: The Doppler effect happens when a source of sound or light is moving relative to an observer. When you're standing next to a highway and a semitrailer zooms past, the pitch of its engine suddenly drops when the sound waves start being stretched as the truck moves away from you. Same with the light of distant stars. A higher Doppler shift indicates a faster truck -- or star.)
If the results survive further scrutiny, the photos of these two galaxies would be the earliest direct evidence of conditions soon after the Big Bang. You remember: The mind-bogglingly huge explosion in which a, an, er, well, something really tiny, exploded and blossomed into everything there is -- or at least, the predecessor of everything that is? What happened next is a bit murky: The first billion years of the universe are a dark spot. Maybe there were no stars. Maybe there were stars, but their light was blocked by immense clouds of hydrogen gas, and could not reach us across the billions of light years and billions of time-years separating us from the primitive universe.
As universe expands, explanation wanted
You might think that by now we would have a rough idea of what's in the universe. True, except for two itsy-bitsy problems: dark matter, and dark energy. About 30 years ago, astronomers realized the galaxies were spinning too fast: The mass of their stars would not make enough gravity to hold them together. Long ago, they should have spun to smithereens. Astronomers cooked up "dark matter" as the source of gravity to prevent that unseemly outcome. Dark matter: Convenient jargon for "stuff we can't see"...
Since dark matter was s'posed to be way more common than the stuff we could see, dark matter mattered. Now we hear of another trifling omission: Why did the expansion of the universe start speeding up about 7 billion years ago? Theunexpected action on the gas pedal (for 70 years, astronomers thought gravity would be slowing the expansion ) has astronomers scrambling for an explanation. Meet "dark energy." This illuminating name masks a pathetic inability to explain exactly why the universe would be expanding. To skeptics, dark energy seems nothing more than a polite way of saying, "I have no answer to your question about why the universe is expanding faster."
We'll return to dark energy, but first, what's new with old galaxies?
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2 3 pages in this feature. Terry Devitt, editor; Sarah Goforth, project assistant; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive ©2004, University of Wisconsin, Board of Regents. |
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