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In the case of an earth-like planet (considering not just composition and size, but also orbit + host star similarity) that's difficult to do when the transit o

In the case of an earth-like planet (considering not just composition and size, but also orbit + host star similarity) that's difficult to do when the transit only occurs every 365 days Even finding just one such planet will require a lot of observation: The "geometric probability" of the orbital plane being aligned for an earth-like orbit seems to be around 0.5% [0]. Assuming every star has an earthlike planet [1], only 1 in 200 observed stars will be correctly aligned. So observing 365*200=73,000 stars over an entire day (also not possible for ground-based telescopes due to the day/night cycle) should statistically result in one transit observation. The transit duration is also a problem, for an earth-like exoplanet it is 13 hours, so if the observation time is too short, one would only catch the beginning or end of the transit [0] https://www.researchgate.net/figure/Transit-Properties-for-Solar-System-Objects_tbl1_226590554 https://www.researchgate.net/figure/Transit-Properties-for-S... [1] The current hypothesis seems to be that every star has at least one planet https://en.wikipedia.org/wiki/Planet-hosting_star https://en.wikipedia.org/wiki/Planet-hosting_star), but it's all a bit up in the air as not many exoplanets (and especially earth-like ones) have been observed yet. The sample size is too low.

zuminator 3y ago
> The current hypothesis seems to be that every star has at least one planet I think you mean, that stars have at least one planet on average. E.g. in the unlikely event that only one third of stars had planets, but each one of those stars had on average 3 stars, then it would fit the hypothesis of averaging at least one planet per star. It's not a stretch at all since our rather boring star has at least 8 planets, and of the 4,051 stars we can currently detect with exoplanets, they have a total of 5,438 planets, meaning over 1.34 planets per star not including the unknown but unquestionably vast number of planets we currently don't have the capability of detecting. Still, just as we suspect large numbers of rogue planets that have lost their stars, there must be at least some stars out there that have lost their planets, whether to passing neutron stars or perhaps indigestion. [0] https://en.wikipedia.org/wiki/Lists_of_exoplanets#:~:text=These%20are%20,systems https://en.wikipedia.org/wiki/Lists_of_exoplanets#:~:text=Th...

zuminator 3y ago

> The current hypothesis seems to be that every star has at least one planet I think you mean, that stars have at least one planet on average. E.g. in the unlikely event that only one third of stars had planets, but each one of those stars had on average 3 stars, then it would fit the hypothesis of averaging at least one planet per star. It's not a stretch at all since our rather boring star has at least 8 planets, and of the 4,051 stars we can currently detect with exoplanets, they have a total of 5,438 planets, meaning over 1.34 planets per star not including the unknown but unquestionably vast number of planets we currently don't have the capability of detecting. Still, just as we suspect large numbers of rogue planets that have lost their stars, there must be at least some stars out there that have lost their planets, whether to passing neutron stars or perhaps indigestion. [0] https://en.wikipedia.org/wiki/Lists_of_exoplanets#:~:text=These%20are%20,systems https://en.wikipedia.org/wiki/Lists_of_exoplanets#:~:text=Th...