NH Notes: More Planets Than Stars Update

Artist’s representation of the “habitable zone,” the range of orbits where liquid water is permitted on the surface of a planet. The authors find that 22% of Sun-like stars harbor a planet between one and two times the size of Earth in the habitable zone. (Credit: Petigura/UC Berkeley, Howard/UH-Manoa, Marcy/UC Berkeley)

Artist’s representation of the “habitable zone,” the range of orbits where liquid water is permitted on the surface of a planet. The authors find that 22% of Sun-like stars harbor a planet between one and two times the size of Earth in the habitable zone. (Credit: Petigura/UC Berkeley, Howard/UH-Manoa, Marcy/UC Berkeley)d

Our solar system comes with planets of all sorts of sizes and compositions.   Not long ago, it was possible to debate if there were any other planets in the Universe other than those of our solar system.   Now, there doesn’t seem to be any question that other planets, called exoplanets, do exist. The question now is how many and what do they look like.   The latter question is difficult but becoming increasing possible to answer.   The first planets identified were inferred to be massive gas giants like Jupiter and Saturn but with more experience and more precise instruments the ability to identify planets in the so-called habitable zone around stars has become increasingly possible.  The habitable zone refers to the region of space that is neither too close or too far away from a sun/star for conditions on that planet to be earth-like.  This only means that liquid water and an atmosphere would be possible not that all planets in this zone would have these characteristics.

In a previous article (More Planets than Stars: Exoplanets and Our Little Blue Planet)  I reported a first estimate of the number of these earth-like planets in our galaxy and explored some of the theological and scientific implications.  I refer you back to that post for my thoughts on the significance of these findings. I only wish to report an update here on the current estimates of habitable planets in the Universe.   At the time of my previous article I had said that data at the time suggested that there could be as many as 1 sextillion earth-like (size and distance from a sun like ours) planets in the Universe.  A new and more rigorous analysis puts that number a bit lower but not by much.   The authors of this recent analysis estimate 22% of sun-like stars in our galaxy have planets in the “habitable” zone.  That would mean that there are 8 to 10 billion planets 1-2 times the size of earth in this zone around stars just in our own milky way galaxy. With these new numbers we could extrapolate that out to a Universe with 80 to 400 quintillion earth-like planets.    Writing that out to show how mind-boggling big that number is you get:  400,000,000,000,000,000,000 planets.  There would probably be 10 times as many total planets that are more like Mercury or Saturn that Earth-like planets thus giving us an estimated 4 sextillion total planets in the Universe give or take a few sextillion:-)   The numbers are so large it would probably be just simply to say that it now appears that there are a gazillion or an uncountable number of planets in the Universe.

In Genesis 26:4 God told Abraham:  “I will make your descendants as numerous as the stars in the sky.”  The point was that his descendants would be an uncountable number.  If God were communicating to today’s audience He could well have said that He would make Abrahams’ descendants as numerous as the planets in the Universe.  This is an example of where God is speaking both literally and figuratively at the same time.  Literally if we take the intent of his words to mean “uncountable” (this what he literally meant in his communication) but figuratively in that we know that his descendants will never literally number in the sextillions.

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