The Visible Universe: "Seven Trillion Dwarfs and Billions of Undetected Galaxies" (Weekend Feature)

The European Space Agency’s Herschel space telescope has discovered that previously unseen distant galaxies are responsible for a cosmic fog of infrared radiation. The galaxies are some of the faintest and furthest objects seen by Herschel, and opened a new window on the birth of stars in the early Universe.

Astronomers estimate that their are billions and billions of galaxies in the observable universe (as well as some seven trillion dwarf galaxies) . Here's how astronomers breakout the visible universe within 14 billion light years:

Superclusters in the visible universe = 10 million

Galaxy groups in the visible universe = 25 billion

Large galaxies in the visible universe = 350 billion

Dwarf galaxies in the visible universe = 7 trillion

Stars in the visible universe = 30 billion trillion (3x10²²)

Astronomers realized this past year that they may have underestimated the number of galaxies in some parts of the universe by as much as 90 percent, according to a study in 2011 by Matthew Hayes of the University of Geneva's observatory, who led the investigation using the world's most advanced optical instrument -- Europe's Very Large Telescope (VLT) in Chile, which has four 8.2-meter (26.65-feet) behemoths. They turned two of the giants towards a well-studied area of deep space called the GOODS-South field.

In the case of very distant, old galaxies, the telltale light may not reach Earth as it is blocked by interstellar clouds of dust and gas -- and, as a result, these galaxies are missed by the map-makers.
"Astronomers always knew they were missing some fraction of the galaxies... but for the first time we now have a measurement. The number of missed galaxies is substantial," said Matthew Hayes of the University of Geneva's observatory, who led the investigation.

more here: http://www.dailygalaxy.com/my_weblog/2013/02/the-visible-universe-seven-trillion-dwarfs-and-billions-of-undetected-galaxies-weekend-feature.html