(Hypothetical Concept) But is it possible to depend on a white dwarf as our power source? Provided we harness its 99% of energy? Can life be sustained?(If it is possible we can easily colonize an exoplanet which is located at a suitable distance from dwarf star)
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6$\begingroup$ I'm voting to close this question as off-topic because it is unrelated to space exploration. $\endgroup$– Organic MarbleCommented Jun 8, 2018 at 21:22
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1$\begingroup$ This might work on Worldbuilding. For this site it's far too speculative. $\endgroup$– kim holderCommented Jun 9, 2018 at 0:48
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The Dyson-sphere is gravitationally unstable. The planets have a circular orbit, but a the Dyson-sphere is a sphere. Where could it rotate? It doesn't matter, on the poles it would fall into the star.
The current technological reality is that the fusion energy, and then heating and lighting a planet with it, is not far from being possible. We could do in same decades, we would only need a peaceful, well-organized humanity for that :-)
But building a Dyson-sphere is far, far away. There is nothing from which it could be built.
However, a planet having life around a white dwarf is possible even without such things. The power what it gets from its Sun, increases quadratically with the recipe of the distance. I.e. if the planet is halfway to the star, it gets 4 times more power.
An imaginary solar system, whose star is a white dwarf with the power output of 1% of the Sun, may have habitable planets 15million km from it. (The Earth-Sun distance is 150million km.)
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$\begingroup$ A paragraph could have been inserted about the tidal locking, but it is a sad friday afternoon and I think the OP is not interested in so deep details. $\endgroup$– peterhCommented Jun 8, 2018 at 23:43
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1$\begingroup$ There have been some recent articles that suggest the radiation flux from a white dwarf is far too high to sustain life in its habitable zone. $\endgroup$– HobbesCommented Jun 9, 2018 at 12:22
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$\begingroup$ @Hobbes I am surprised on that, a white dwarf is a black body radiator with not a very big temperature. Maybe it gives far more ultraviolet light, if it is a young one. $\endgroup$– peterhCommented Jun 9, 2018 at 12:28
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1$\begingroup$ I might be misremembering. I'll see what I can dig up. $\endgroup$– HobbesCommented Jun 9, 2018 at 13:21
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$\begingroup$ @Hobbes Young white dwarves can be hotter as the Sun, thus while they give the same power output, it comes in larger part in UV. This may be a huge problem. However, they don't make coronal ejections and similar. The increased power output would also result an increased ozone concentration on an imaginary habitable planet around it. I think it depends on, how the protection of the ozone layer depends on the increased UV. $\endgroup$– peterhCommented Jun 10, 2018 at 17:20