Using NASA’s Kepler data, they estimate 1 Earth for every 5 Suns:
“My calculations place an upper limit of 0.18 Earth-like planets per G-type star,” says UBC researcher Michelle Kunimoto, co-author of the new study in The Astronomical Journal. “Estimating how common different kinds of planets are around different stars can provide important constraints on planet formation and evolution theories, and help optimize future missions dedicated to finding exoplanets.”
According to UBC astronomer Jaymie Matthews: “Our Milky Way has as many as 400 billion stars, with seven per cent of them being G-type. That means less than six billion stars may have Earth-like planets in our Galaxy.”
Previous estimates of the frequency of Earth-like planets range from roughly 0.02 potentially habitable planets per Sun-like star, to more than one per Sun-like star.
Typically, planets like Earth are more likely to be missed by a planet search than other types, as they are so small and orbit so far from their stars. That means that a planet catalogue represents only a small subset of the planets that are actually in orbit around the stars searched. Kunimoto used a technique known as ‘forward modelling’ to overcome these challenges.
“I started by simulating the full population of exoplanets around the stars Kepler searched,” she explained. “I marked each planet as ‘detected’ or ‘missed’ depending on how likely it was my planet search algorithm would have found them. Then, I compared the detected planets to my actual catalogue of planets. If the simulation produced a close match, then the initial population was likely a good representation of the actual population of planets orbiting those stars.”University of British Columbia, “As many as six billion Earth-like planets in our galaxy, according to new estimates” at ScienceDaily
The basic problem is that it’s speculation with numbers. Only a few changes in variable factors are needed to upset such reasoning.
There’s got a reason why so much science is beginning to sound like the National Enquirer for STEM nerds. But we are waiting for the Big Explain book to come out. Should be a classic.
The 36 intelligent civilizations? See also: New “Astrobiological Copernican Limit” claims 36 intelligent civilizations. It’s all malarkey. In the real world, it would be awfully nice to find fossil bacteria on Mars. When that seems to be taking some time, we hear about 36 alien civs. That’s because there’ll always be a market for We Are Not Alone. The thing is, it used to be called religion, not science. And it still IS religion, not science.