News Stories

Found: 7 Percent of the Universe

Newswise - A big part of the universe has been missing for 10 billionyears, since the time when the stars first formed, but nowscientists have solved the mystery. Where is it? It'sfloating in super-hot rivers of gas that are invisible tothe naked eye, surrounding galaxies like our own. And acompletely different kind of mystery matter?dark matter?mayhave put it there.

The current issue of Nature reports that astronomers workingwith NASA's Chandra X-ray Observatory found the missingmatter. They had previously detected the rivers of gas withthe X-ray telescope, but this is the first time they've beenable to study it in enough detail to figure out how much isthere. And guess what? The amount matches the amount ofmaterial that's been missing for the past 10 billion years.

Scientists now think that when the universe began, itcontained a certain amount of normal matter?the protons andneutrons that today make up all normal atoms. Astronomerscan use optical telescopes to look back in time and see whathappened to all these normal atoms, called baryons. Around10 billion years ago, when half of the baryons became starsand galaxies, while the other half just seemed to disappear.This new study shows they're still out there, they're justfloating in gas that is too hot to see with an opticaltelescope.

For example, the gas that surrounds our galaxy is 100 timeshotter than the sun?so hot that it shines in X-rays insteadof lower-energy visible light. Before X-ray telescopes wereinvented, astronomers couldn't see this gas?or these atoms.

Are aliens here but we just can't see them? Or maybesome of uscan.

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