The diagram above shows how the total mass of stars in the Universe should have changed over the last 11 billion years based on the new observations (lines) and how it actually did (symbols; different measurements by other teams). This provides an excellent agreement between both and strengthens the prediction of the new results that no more than a further 5% of stars will come into existence, even if we wait forever.

February 03, 2013

“Potential for Life in the Universe –Is It Reaching its Peak?” (Weekend Feature)

The Universe is passing through the stelliferous era –its peak of star formation–but appears to be still peaking in its formation of planets, according to Dimitar Sasselov, Professor of Astronomy at Harvard University and director of the Harvard Origins of Life Initiative. There are more stars in the Universe than there are grains of sand on Earth and there are an equal number of planets.

There are 200 billion stars in the Milky Way and 90% are small enough and old enough to have planets in orbit. And only 10% of these stars were formed with enough heavy elements to have Earth-like planets with 2% of these –or 100 million super-Earths and Earths– will orbit within their star’s habitable zone.
Differing from Sasselov, an important study by an international team of astronomers has established that the rate of formation of new stars in the Universe is now only 1/30th of its peak and that this decline is only set to continue.

The accepted model for the evolution of the Universe predicts that stars began to form about 13.4 billion years ago, or around three hundred million years after the Big Bang. Many of these first stars are thought to have been monsters by today’s standards, and were probably hundreds of times more massive than our Sun. Such beasts aged very quickly, exhausted their fuel, and exploded as supernovae within a million years or so. Lower mass stars in contrast have much longer lives and last for billions of years. Much of the dust and gas from stellar explosions was (and is still) recycled to form newer and newer generations of stars.

Read more: "Potential for Life in the Universe –Is It Reaching its Peak?" (Weekend Feature) — Daily Galaxy.

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