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  2. Nebular hypothesis - Wikipedia

    en.wikipedia.org/wiki/Nebular_hypothesis

    Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded. According to the nebular theory, stars form in massive and dense clouds of molecular hydrogen—giant molecular clouds (GMC). These clouds are gravitationally unstable, and matter coalesces within them to ...

  3. Strömgren sphere - Wikipedia

    en.wikipedia.org/wiki/Strömgren_sphere

    The Rosette Nebula, an example of a Strömgren sphere In theoretical astrophysics , there can be a sphere of ionized hydrogen (H II) around a young star of the spectral classes O or B . The theory was derived by Bengt Strömgren in 1937 and later named Strömgren sphere after him.

  4. Nebula - Wikipedia

    en.wikipedia.org/wiki/Nebula

    The Westbrook Nebula, a protoplanetary nebula. A protoplanetary nebula or preplanetary nebula [ 27 ] (PPN, plural PPNe) is an astronomical object which is at the short-lived episode during a star 's rapid evolution between the late asymptotic giant branch (LAGB) [a] phase and the subsequent planetary nebula (PN) phase.

  5. Formation and evolution of the Solar System - Wikipedia

    en.wikipedia.org/wiki/Formation_and_evolution_of...

    The Ring nebula, a planetary nebula similar to what the Sun will become. This is a relatively peaceful event, nothing akin to a supernova, which the Sun is too small to undergo as part of its evolution. Any observer present to witness this occurrence would see a massive increase in the speed of the solar wind, but not enough to destroy a planet ...

  6. History of Solar System formation and evolution hypotheses

    en.wikipedia.org/wiki/History_of_Solar_System...

    French philosopher and mathematician René Descartes was the first to propose a model for the origin of the Solar System in his book The World, written from 1629 to 1633.. In his view, the universe was filled with vortices of swirling particles, and both the Sun and planets had condensed from a large vortex that had contracted, which he thought could explain the circular motion of the plane

  7. Jeans instability - Wikipedia

    en.wikipedia.org/wiki/Jeans_instability

    The Jeans mass is named after the British physicist Sir James Jeans, who considered the process of gravitational collapse within a gaseous cloud. He was able to show that, under appropriate conditions, a cloud, or part of one, would become unstable and begin to collapse when it lacked sufficient gaseous pressure support to balance the force of gravity.

  8. Interstellar cloud - Wikipedia

    en.wikipedia.org/wiki/Interstellar_cloud

    Reflection nebula IRAS 10082-5647 observed by the Hubble Space Telescope. These interstellar clouds possess a velocity higher than can be explained by the rotation of the Milky Way. [5] By definition, these clouds must have a v lsr greater than 90 km s −1, where v lsr is the local standard rest velocity.

  9. Astrophysical plasma - Wikipedia

    en.wikipedia.org/wiki/Astrophysical_plasma

    Lagoon Nebula is a large, low-density cloud of partially ionized gas. [1] Astrophysical plasma is plasma outside of the Solar System. It is studied as part of astrophysics and is commonly observed in space. [2] The accepted view of scientists is that much of the baryonic matter in the universe exists in this state. [3]