Tidal downsizing is a hypothetical mechanism for the formation of

planets A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young ...

. The process begins with the formation of large clumps of gas, of roughly 10

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandt ...

masses, via

gravitational instability The key idea in explaining the way in which structures evolve in the universe is gravitational instability. If material is to be brought together to form structures, then a long-range force is required, and gravity is the only known possibility. ( ...

in the outer parts of the

protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, ...

. The clumps migrate inward due to gravitational interactions with the gas disk. Solid grains within the clump collide and grow and settle toward the center forming a massive core. The clump is disrupted due to tidal forces or heating from the

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

when it approaches within a few AU of the star leaving behind a smaller object. Depending on the extent and timing of the mass loss the remnant may be a

terrestrial planet A terrestrial planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun: Mercury, ...

, an

ice giant An ice giant is a giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur. There are two ice giants in the Solar System: Uranus and Neptune. In astrophysics and planetary science th ...

or 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" ...

References

{{Reflist Astronomy