Five Hundred Million Planets in Milky Way Alone Theoretically Capable of Sustaining Life

Assuming there is around one planet per star. In many cases there are more than five, our own solar system has eight. There will be some there that have over fifty planets orbiting a star. Many of course would be gas giants or uninhabitable planets of methane but planets that would satisfy the so-called Goldilocks Zone would still number around 50 billion.

Goldilocks Zone

Planets that inhabit a region known as the Goldilocks Zone are planets that would not be too hot or too cold for life to comfortably exist here. Much like our own Earth. In the fairy-tale of Goldilocks and the Three Bears, Goldilocks helped herself to the Bear’s porridge, finding the first one too hot, the second too cold, and the third just right. She had a similar experience with the Bear’s beds. Planets that are too close to the sun it orbits would be too warm for life to exist comfortably here and similarly with planets that orbit too far away from the sun it orbits.

Habitable Planets in the whole Universe

Well so we have found that there are 1,236 planets that Kepler has discovered thus far. Kepler has only touched on 0.25 per cent of the Milky Way. So by using this sample there should be 50 billion planets in the Milky Way. Fifty million of which would be Goldilocks planets. 

Now the math gets hairy. There are estimated to be 100 billion galaxies, many like The Milky Way, in our universe. That means there are around 50 quintillion (that is 5 followed by 19 Zeros) planets that could sustain life in our universe.

Arthur C Clarke

Mr Clarke, novelist and physicist, he is the one who wrote 2001: A Space Odyssey. He once said, “The idea that we are the only intelligent creatures in a cosmos of a hundred billion galaxies is so ridiculous that there are virtually no astronomers today who would take it seriously.”