Star lifting is any of several hypothetical processes by which a highly advanced civilization (at least Kardashev-II) could remove a substantial portion of a star's matter in a controlled manner for other uses. The term appears to have been coined by David Criswell.
Stars already lose a small flow of mass via solar wind, coronal mass ejections, and other natural processes. Over the course of a star's life on the main sequence this loss is usually negligible compared to the star's total mass; only at the end of a star's life when it becomes a red giant or a supernova is a large amount of material ejected. The star lifting techniques that have been proposed would operate by increasing this natural plasma flow and manipulating it with magnetic fields.
Stars have deep gravity wells, so the energy required for such operations is large. For example, lifting solar material from the surface of the Sun to infinity requires 2.1 × 1011 J/kg. This energy could be supplied by the star itself, collected by a Dyson sphere; using only 10% of the Sun's total power output would allow 5.9 × 1021 kilograms of matter to be lifted per year (0.0000003% of the Sun's total mass). The Dyson sphere would need to be designed to allow the lifted material to egress through it.
Read more about Star Lifting: Harvesting Lifted Mass, Stellar Husbandry, In Fiction
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