I was seeing a size comparison video of the size of the Sun with other stars, and I could see there are stars hundreds of times larger than the Sun. I understand the Circumstellar Habitable Zone depends on temperature and luminosity. Given proper temperature and luminosity, Is the Circumstellar Habitable Zone larger for larger stars, or not necessarily? Do some of these giant stars have giant Circumstellar Habitable Zones?


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When our Sun expands into a humungous red giant in a few billion years, the habitable zone will indeed increase in size with it. It is expected to evolve into an AGB (asymptotic giant branch) star, which generally have a couple hundred solar radii. During this phase, it will be a cold M-Type star, but its utterly gigantic surface area will make up for its temperature, far exceeding the Sun's current energy output - even though it is a nice toasty G2V.

With that being said, colder planets like Jupiter and Saturn will heat up, theoretically becoming temperate or similar to Earth's current climate depending on how big the Sun ends up becoming. As for Earth itself, if it isn't completely engulfed, will be absolutely scorched by the now nearby surface.

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    $\begingroup$ Due to the Sun's gradually increasing luminosity, the Earth will be uninhabitable in a billion years or so, well before the Sun becomes a red giant. See en.wikipedia.org/wiki/… $\endgroup$
    – PM 2Ring
    Commented Jan 8 at 22:41
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    $\begingroup$ Thank you for the reference. By "will no longer be suitable for life after this event", I just meant that the red giant will essentially finish sealing the planet's fate, not inherently cause it. To clarify, I will rephrase that segment to make it more concise, thanks again for the information. $\endgroup$
    – 4NT4R3S
    Commented Jan 8 at 22:51

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