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Most Earth-Like Worlds Are Unborn

Credit: ESA/NASA

An artist's impression of innumerable Earth-like planets that have yet to be born over the next trillion years in the evolving universe. Credit: ESA/NASA

Astronomers have peered behind the Milky Way and determined that 92% of habitable planets have not yet been born.

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An assessment of data collected by NASA’s Hubble Space Telescope and the Kepler space observatory has determined that only 8% of the potentially habitable planets that will ever form in the universe existed when our solar system was born 4.6 billion years ago.

“Our main motivation was understanding the Earth’s place in the context of the rest of the universe,” said study author Peter Behroozi of the Space Telescope Science Institute in Baltimore. “Compared to all the planets that will ever form in the universe, the Earth is actually quite early.”

Looking far back in time, Hubble has given astronomers a “family album” of galaxy observations that chronicle the universe’s star formation history as galaxies grew. The data show that the universe was making stars at a fast rate 10 billion years ago, but the fraction of the universe’s hydrogen and helium gas that was involved was very low.

Today, star birth is happening at a much slower rate than long ago, but there is so much leftover gas available that the universe will keep cooking up stars and planets for a very long time to come.

Kepler’s planet survey indicates that Earth-sized planets in a star’s habitable zone, the perfect distance that could allow water to pool on the surface, are everywhere in our galaxy. Scientists predict that there should be one billion Earth-sized worlds in the Milky...

The full text of this article can be purchased from Informit.