Hundreds of billions of Earth-like planets may host alien life

A team of scientists estimates that there may be hundreds of billions of Earth-like planets in the Milky Way galaxy that can support alien life.

New studies and new projections are frequently published by researchers because incredible space tools, like NASA’s Kepler space telescope, are providing scientists with more data than has ever been available. For example, in 2012, astronomers analyzed data from the European Southern Observatory’s HARPS (High Accuracy Radial velocity Planet Searcher) planet-hunting telescope, and concluded that there could be tens of billions of Earth-like planets in our galaxy. And, in 2014, a research team evaluated the list of confirmed exoplanets, leading to the conclusion that the Milky Way is home to one hundred million planets that could support complex alien life.

Artist’s illustration of Kepler. (Credit: NASA Ames/ W Stenzel)

For this recent study, scientists applied an idea known as the Titius-Bode hypothesis to the exoplanets detected by Kepler. Science World Report explains, “The Titius-Bode relation is a hypothesis that the bodies in some orbital systems, including the sun’s, orbit at semi-major axes in a function of planetary sequence.”

Kepler’s observation method makes it biased towards detecting planets that are very close to their stars. So scientists applied the 200-year-old Titius-Bode idea to Kepler’s data. “We used the Titius-Bode relation and Kepler data to predict the positions of planets that Kepler is unable to see,” says Associate Professor Charley Lineweaver from The Australian National University.

The results lead researchers to conclude that “the standard star has about two planets in the so-called goldilocks zone, the distance from the star where liquid water, crucial for life, can exist.”

Habitable zone predictions. (Credit: ANU)

Lineweaver states, “The ingredients for life are plentiful, and we now know that habitable environments are plentiful.”

But he speculates, “However, the universe is not teeming with aliens with human-like intelligence that can build radio telescopes and space ships. Otherwise we would have seen or heard from them. It could be that there is some other bottleneck for the emergence of life that we haven’t worked out yet. Or intelligent civilisations evolve, but then self-destruct.”

The team’s findings are published in the journal Monthly Notices of the Royal Astronomical Society.

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