How many worlds exist in our galaxy?


Estimating the number of worlds (planets) in our galaxy involves several scientific and probabilistic calculations. According to Sara Seager, an expert discussed on the Lex Fridman Podcast, the variable to consider includes the number of stars accessible to surveys and the characteristics that make those stars likely to host planets. For instance, she mentions looking specifically at around 30,000 red dwarf stars in one project, highlighting that this is just a subset of a much larger number of stars which could potentially host planets 1.

Additionally, discussions on the podcast indicate that many stars are likely to have habitable planets. This high probability stems from extensive data from missions like the Kepler space telescope, which observed that a significant fraction of stars in the Milky Way galaxy probably have planets in their habitable zones 2.

Thus, while an exact number is hard to pinpoint due to numerous variables and uncertainties, it is likely that there are billions of planets in the Milky Way galaxy that could be considered "worlds" under current astronomical criteria and observations.

Habitable Planets

Sara explains her equation for determining the number of inhabited planets that show signs of life and breaks down the variables involved, including the number of stars available and the fraction of those stars that are quiet and can be searched for planets.

Lex Fridman Podcast

Sara Seager: Search for Planets and Life Outside Our Solar System | Lex Fridman Podcast #116

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