Star lifting is any of several hypothetical processes by which a sufficiently advanced civilization (specifically, one of
Kardashev-II or higher) could remove a substantial portion of a
star's matter which can then be re-purposed, while possibly optimizing the star's energy output and lifespan at the same time. The term appears to have been coined by
David Criswell
David R. Criswell (July 17, 1941 – September 10, 2019) was the Director of the Institute for Space Systems Operations at the University of Houston. ISSO is the operational agent for the Houston Partnership for Space Exploration.
Criswell receiv ...
.
Stars already lose a small flow of mass via
solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sol ...
,
coronal mass ejection
A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accept ...
s, 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 proportion 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 well
The Hill sphere of an astronomical body is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere. That moon would, in turn, have a Hil ...
s, so the energy required for such operations is large. For example, lifting solar material from the surface of the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
to infinity requires 2.1
× 1011 J/
kg. This energy could be supplied by the star itself, collected by a
Dyson sphere
A Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures a large percentage of its solar power output. The concept is a thought experiment that attempts to explain how a spacefaring civilization would meet ...
; using 10% of the Sun's total power output would allow 5.9 × 10
21 kilograms of matter to be lifted per year (0.0000003% of the Sun's total mass), or 8% of the mass of
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
's
moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
.
Methods for lifting material
Thermal-driven outflow
The simplest system for star lifting would increase the rate of solar wind outflow by directly heating small regions of the star's atmosphere, using any of a number of different means to deliver energy such as
microwave
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...
beams,
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...
s, or
particle beam
A particle beam is a stream of charged or neutral particles. In particle accelerators, these particles can move with a velocity close to the speed of light. There is a difference between the creation and control of charged particle beams and ne ...
s – whatever proved to be most efficient for the engineers of the system. This would produce a large and sustained eruption similar to a
solar flare
A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other sol ...
at the target location, feeding the solar wind.
The resulting outflow would be collected by using a
ring current
A ring current is an electric current carried by charged particles trapped in a planet's magnetosphere. It is caused by the longitudinal drift of energetic (10–200 k eV) particles.
Earth's ring current
Earth's ring current is responsible f ...
around the star's equator to generate a powerful
toroidal magnetic field with its
dipole
In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways:
*An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system ...
s over the star's rotational poles. This would deflect the star's solar wind into a pair of jets aligned along its rotational axis passing through a pair of magnetic rocket
nozzles. The
magnetic nozzle A magnetic nozzle is a convergent-divergent magnetic field that guides, expands and accelerates a plasma jet into vacuum for the purpose of space propulsion. The magnetic field in a magnetic nozzle plays a similar role to the convergent-divergent ...
s would convert some of the plasma's thermal energy into outward velocity, helping cool the outflow. The ring current required to generate this magnetic field would be generated by a ring of
particle accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams.
Large accelerators are used for fundamental research in particle ...
space stations in close orbit around the star's equator. These accelerators would be physically separate from each other but would exchange two counterdirected beams of oppositely charged
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
s with their neighbor on each side, forming a complete circuit around the star.
"Huff-n-Puff"
David Criswell
[ ] proposed a modification to the polar jet system in which the magnetic field could be used to increase solar wind outflow directly, without requiring additional heating of the star's surface. He dubbed it the "Huff-n-Puff" method, inspired from the Big Bad Wolf's threats in the fairy tale of ''
Three Little Pigs
"The Three Little Pigs" is a fable about three pigs who build three houses of different materials. A Big Bad Wolf blows down the first two pigs' houses which made of straw and sticks respectively, but is unable to destroy the third pig's house ...
''.
In this system the ring of particle accelerators would not be in orbit, instead depending on the outward force of the magnetic field itself for support against the star's gravity. To inject energy into the star's atmosphere the ring current would first be temporarily shut down, allowing the particle accelerator stations to begin falling freely toward the star's surface. Once the stations had developed sufficient inward velocity the ring current would be reactivated and the resulting magnetic field would be used to reverse the stations' fall. This would "squeeze" the star, propelling stellar atmosphere through the polar magnetic nozzles. The ring current would be shut down again before the ring stations achieved enough outward velocity to throw them too far away from the star, and the star's gravity would be allowed to pull them back inward to repeat the cycle.
A single set of ring stations would result in a very intermittent flow. It is possible to smooth this flow out by using multiple sets of ring stations, with each set operating in a different stage of the Huff-n-Puff cycle at any given moment so that there is always one ring "squeezing". This would also smooth out the power requirements of the system over time.
Centrifugal acceleration
An alternative to the Huff-n-Puff method for using the toroidal magnetic field to increase solar wind outflow involves placing the ring stations in a polar orbit rather than an equatorial one. The two magnetic nozzles would then be located on the star's equator. To increase the rate of outflow through these two equatorial jets, the ring system would be rotated around the star at a rate significantly faster than the star's natural rotation. This would cause the stellar atmosphere swept up by the magnetic field to be flung outward.
This method suffers from a number of significant complications compared to the others. Rotating the ring in this manner would require the ring stations to use powerful rocket thrust, requiring both large
rocket
A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...
systems and a large amount of
reaction mass
Working mass, also referred to as reaction mass, is a mass against which a system operates in order to produce acceleration.
In the case of a chemical rocket, for example, the reaction mass is the product of the burned fuel shot backwards to prov ...
. This reaction mass can be "recycled" by directing the rockets' exhausts so that it impacts the star's surface, but harvesting fresh reaction mass from the star's outflow and delivering it to the ring stations in sufficient quantity adds still more complexity to the system. Finally, the resulting jets would spiral outward from the star's equator rather than emerging straight from the poles; this could complicate harvesting it, as well as the arrangement of the
Dyson sphere
A Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures a large percentage of its solar power output. The concept is a thought experiment that attempts to explain how a spacefaring civilization would meet ...
powering the system.
Harvesting lifted mass
The material lifted from a star will emerge in the form of plasma jets hundreds or thousands of
astronomical unit
The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits ...
s long, primarily composed of
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
and
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
and highly diffuse by current engineering standards. The details of extracting useful materials from this stream and storing the vast quantities that would result have not been extensively explored. One possible approach is to purify useful elements from the jets using extremely large-scale
mass spectrometry, cool them by
laser cooling
Laser cooling includes a number of techniques in which atoms, molecules, and small mechanical systems are cooled, often approaching temperatures near absolute zero. Laser cooling techniques rely on the fact that when an object (usually an atom) a ...
, and condense them on particles of dust for collection. An alternative method could involve using large
solenoids
upright=1.20, An illustration of a solenoid
upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines
A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...
to slow the jets down and separate out the components. Electricity would also be generated via this system. Small artificial
gas giant
A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...
planets could be constructed from excess hydrogen and helium to store it for future use. Excess gas could also be used to build new earthlike planets to custom specifications.
Stellar husbandry
The lifespan of a star is determined by the size of its supply of nuclear "fuel" and the rate at which it uses up that fuel in
fusion
Fusion, or synthesis, is the process of combining two or more distinct entities into a new whole.
Fusion may also refer to:
Science and technology Physics
*Nuclear fusion, multiple atomic nuclei combining to form one or more different atomic nucl ...
reactions in its core. Larger stars have a larger supply of fuel, but the increased core pressure resulting from that additional mass increases the reaction rate even more; large stars have a significantly shorter lifespan than small ones. Current theories of stellar dynamics also suggest that there is very little mixing between the bulk of a star's atmosphere and the material of its core, where fusion takes place, so most of a large star's fuel will never be used naturally. Small
red dwarf stars, which are naturally fully convective, allow their core helium to mix with the outer layers of hydrogen which allows extremely long stellar lifespans on the order of trillions of years.
As a star's mass is reduced by star lifting its rate of nuclear fusion will decrease, reducing the amount of energy available to the star lifting process but also reducing the gravity that needs to be overcome. Theoretically, it would be possible to remove an arbitrarily large portion of a star's total mass given sufficient time. In this manner a civilization could control the rate at which its star uses fuel, optimizing the star's power output and lifespan to its needs. The hydrogen and helium extracted in the process could also be used as fusion reactor fuel. Alternatively, the material could be assembled into additional smaller stars, to improve the efficiency of its use. Theoretically, most of the energy stored in the matter lifted from a star could be harvested if it is made into small
black holes, via the mechanism of
Hawking radiation
Hawking radiation is theoretical black body radiation that is theorized to be released outside a black hole's event horizon because of relativistic quantum effects. It is named after the physicist Stephen Hawking, who developed a theoretical a ...
.
In fiction
*In the series ''
Stargate Universe
''Stargate Universe'' (often abbreviated as ''SGU'') is a military science fiction television series and part of MGM's ''Stargate'' franchise. It follows the adventures of a present-day, multinational exploration team traveling on the Ancient ...
'', the Ancient ship Destiny and the seed ships sent 2,000 years before Destiny are fueled by plasma from stars. The ship skims over the surface of a star just before dipping below the star's photosphere to scoop in plasma using its retractable collectors.
*In the ''
Star Wars'' franchise of ''
Knights of the Old Republic'', the Star Forge is capable of star lifting. In a way, Starkiller Base in the seventh canonical film star lifts in order to power its planet-destroying laser cannon, although it consumes the entire star to do so.
*The novel ''
Star Trek: Voyager –
The Murdered Sun'' featured a reptilian race using the material from a star to sustain the opening of a
wormhole
A wormhole ( Einstein-Rosen bridge) is a hypothetical structure connecting disparate points in spacetime, and is based on a special solution of the Einstein field equations.
A wormhole can be visualized as a tunnel with two ends at separate p ...
. However, the novel depicted the process as shortening the star's lifespan precipitously rather than extending it.
*In ''
The Night's Dawn Trilogy
British author Peter F. Hamilton's ''The Night's Dawn Trilogy'' consists of three science fiction novels: '' The Reality Dysfunction'' (1996), ''The Neutronium Alchemist'' (1997), and '' The Naked God'' (1999). A collection of short stories, ...
'' by
Peter F. Hamilton, the alien species the Kiint created an arc of custom made planets around their sun from mass extracted from their star.
*In the
Doctor Who episode "
42" the crew of the starship ''Pentallian'' use a
Sun scoop to draw matter from a star to use as fuel for their ship.
*In the novella ''
Palimpsest
In textual studies, a palimpsest () is a manuscript page, either from a scroll or a book, from which the text has been scraped or washed off so that the page can be reused for another document. Parchment was made of lamb, calf, or kid skin an ...
'' by
Charles Stross
Charles David George "Charlie" Stross (born 18 October 1964) is a British writer of science fiction and fantasy. Stross specialises in hard science fiction and space opera. Between 1994 and 2004, he was also an active writer for the magazine '' ...
, the Stasis uses star lifting to replace the core of the Sun with a black hole, producing a "necrostar" with vastly expanded lifespan.
*In the novel ''
The Time Ships
''The Time Ships'' is a 1995 hard science fiction novel by Stephen Baxter. A canonical sequel to the 1895 novella ''The Time Machine'' by H. G. Wells, it was officially authorized by the Wells estate to mark the centenary of the original's pub ...
'' by
Stephen Baxter, the Morlocks create a Dyson sphere inside the orbit of Earth using matter lifted from the Sun.
*In the short story ''
The Golden Apples of the Sun
''The Golden Apples of the Sun'' is an anthology of 22 short stories by American writer Ray Bradbury. It was published by Doubleday & Company in 1953.
The book's title is also the title of the final story in the collection. The words "the go ...
'' by
Ray Bradbury
Ray Douglas Bradbury (; August 22, 1920June 5, 2012) was an American author and screenwriter. One of the most celebrated 20th-century American writers, he worked in a variety of modes, including fantasy, science fiction, horror, mystery fictio ...
, humans fly the rocket Copa de Oro to the Sun and dip a mechanical cup into it to capture the star's warmth for Earth.
*In the video game series ''
Destiny
Destiny, sometimes referred to as fate (from Latin ''fatum'' "decree, prediction, destiny, fate"), is a predetermined course of events. It may be conceived as a predetermined future, whether in general or of an individual.
Fate
Although often ...
'', the mechanical race known as the Vex use star lifts to artificially extend the life of their Forge Star
2082 Volantis.
References
*''Interstellar Migration and the Human Experience'', editors Ben R. Finney and Eric M. Jones, University of California Press, {{ISBN, 0-520-05898-4, Chapter 4: Solar System Industrialization, by David R. Criswell
Star Liftingby Isaac Arthur
Hypothetical technology
Megastructures
Lifting