A gas torus is a toroidal cloud of gas or

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

that encircles a planet. In the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

, gas tori tend to be produced by the interaction of a satellite's

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

with the

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

of a planet. The most famous example of this is the

Io plasma torus The magnetosphere of Jupiter is the cavity created in the solar wind by the planet's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosp ...

, which is produced by the ionization of roughly 1 ton per second of oxygen and sulfur from the tenuous atmosphere of Jupiter's volcanic moon Io. Before being ionized, these particles are part of a neutral torus, also centered on the orbit of Io. Energetic particle observations also suggest the presence of a neutral torus around the orbit of Jupiter's moon

Europa Europa may refer to: Places * Europe * Europa (Roman province), a province within the Diocese of Thrace * Europa (Seville Metro), Seville, Spain; a station on the Seville Metro * Europa City, Paris, France; a planned development * Europa Cliff ...

although such a torus would be merged with the outer portions of an Io torus. Other examples include the largely neutral torus of oxygen and hydrogen produced by Saturn's moon

Enceladus Enceladus is the sixth-largest moon of Saturn (19th largest in the Solar System). It is about in diameter, about a tenth of that of Saturn's largest moon, Titan. Enceladus is mostly covered by fresh, clean ice, making it one of the most refl ...

. The Enceladus and Io tori differ in that particles in the Io torus are predominantly ionized while in the Enceladus torus, the neutral density is much greater than the ion density. After the Voyager encounters, the possibility of a torus of

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

produced by Saturn's moon Titan was proposed. Subsequent observations by the Cassini spacecraft showed no clear evidence of such a torus. While neutral nitrogen could not be measured, the ions near the orbit of Titan were primarily hydrogen or water group (O⁺, OH⁺, H₂O⁺ and H₃O⁺) from the Enceladus torus. Trace amounts of nitrogen ions were detected but at levels consistent with an Enceladus source. A fictional gas torus is the setting for

Larry Niven Laurence van Cott Niven (; born April 30, 1938) is an American science fiction writer. His best-known works are ''Ringworld'' (1970), which received Hugo, Locus, Ditmar, and Nebula awards, and, with Jerry Pournelle, ''The Mote in God's Eye'' ...

's novels ''

The Integral Trees ''The Integral Trees'' is a 1984 science fiction novel by American writer Larry Niven (first published as a serial in ''Analog'' in 1983). Like much of Niven's work, the story is heavily influenced by the setting: a gas torus, a ring of air arou ...

'' and '' The Smoke Ring'', in which a

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" ...

in orbit around a

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...

generates a gas torus of sufficient density and free oxygen to support life (including humans).

External links

''Life in a gas torus around a neutron star'' worldbuilding.stackexchange.com

''Gas torus'' academic.microsoft.com

Notes

{{DEFAULTSORT:Gas Torus Astrophysics