habitable zones for star types in miles ?

[Keklas Rekobah]

Whipsnade: How wide the HZ? About 4130 A.U.
Sudnadja: Which ruleset? This was based on "In The Real-World" (ITRW) Values.

Spectral Class: O0
Luminosity Type: Ia0 or I0
Mass: ~160 Sols
Luminosity: ~34,100,000 Sols
Radius: ~80.2 Sols
Temperature: ~50,000°K

9000-year long seasons ... that's longer than any recorded ITRW polity.

Given that ITRW, 12,000 years have passed since the advent of agriculture (~10,000 BCE), the domestication of animals, and village communities, a 27,000-year period is not too much to imagine a global civilization rising, stabilizing, and then falling into oblivion, especially if the people were confined to only the northern or southern hemisphere.

I supposed that one could develop a history that goes back about 8-1/2 "years" ago, to the "Big War of the Winged Gods"...

 

[Timerover51]

Those orbital periods are fascinating. As Whip points out, a 9000-year-long winter brings a whole new dimension to planetary life. Hmmm....I'm going to have to yoink this idea and play with it for my next game.

That is not that much shorter since the end of the last Ice Age. Depending on the axial tilt to the star, you could have recurring mini-Ice Ages in the northern and southern hemispheres, with considerable pressure of maximum adaptability on the part of plant and animal life, as well as any intelligent life. As the Spring, Summer, and Fall would run about 27,000 years, that would be more than enough time for major civilizations to develop in the non-winter hemisphere.

 

[Keklas Rekobah]

Just keep in mind that the lifetime of a hypergiant is very short in astronomical timescales: only a few million years compared to around 10 billion years for stars like the Sun.

Earth's Hadean Era lasted some 600 million years. This means that any planet that formed in the HZ along with an O0-I0 star would still be in a molten or semi-molten state by the time the star went supernova. A habitable planet would likely be a captured 'Rogue' planet.

If a habitable planet was at the stated "sweet spot" orbit, it would need a very extensive cloud cover to block the star's UV flux. Otherwise, not only would the entire surface be sterilized, but the ionizing properties of the UV would prevent any complex molecules from forming (other than metal-silicates). No amino acids, no DNA, no proteins ... no native life.

I envision a possible captured world of size 9 or 10 (A) orbiting near the outer edge of the HZ, with a thick atmosphere (ATM 8 or 9) blocking the UV and providing just enough of a greenhouse effect to keep the planet warm enough to have liquid water. Jonkereen might tolerate the environment, but pure-strain humans might need to wear something with SPF-2000.

The star would be seen from the ground as a large patch of blue-white brightness in the cloud cover. Space vessels might have to navigate solely by radar and heavily-filtered optics.