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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 not be considered an accretion disk; while the two are similar, an accretion disk is hotter and spins much faster. It is also found on black holes, not stars. This ...
Large disks are routinely observed in many star-forming regions such as the Orion nebula. [18] Artist's impression of the disc and gas streams around young star HD 142527. [53] The lifespan of the accretion disks is about 10 million years. [17] By the time the star reaches the classical T-Tauri stage, the disk becomes thinner and cools. [45]
A protostar is a very young star that is still gathering mass from its parent molecular cloud.It is the earliest phase in the process of stellar evolution. [1] For a low-mass star (i.e. that of the Sun or lower), it lasts about 500,000 years. [2]
A protoplanetary nebula or preplanetary nebula [1] (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) phase and the subsequent planetary nebula (PN) phase. A PPN emits strongly in infrared radiation, and is a kind of reflection nebula.
[8] [9] Every nebula begins with a certain amount of angular momentum. Gas in the central part of the nebula, with relatively low angular momentum, undergoes fast compression and forms a hot hydrostatic (non-contracting) core containing a small fraction of the mass of the original nebula. This core forms the seed of what will become a star. [8]
Over about 100,000 years, [9] the competing forces of gravity, gas pressure, magnetic fields, and rotation caused the contracting nebula to flatten into a spinning protoplanetary disc with a diameter of about 200 AU [11] and form a hot, dense protostar (a star in which hydrogen fusion has not yet begun) at the centre. [25]
In astronomy or planetary science, the frost line, also known as the snow line or ice line, is the minimum distance from the central protostar of a solar nebula where the temperature is low enough for volatile compounds such as water, ammonia, methane, carbon dioxide and carbon monoxide to condense into solid grains, which will allow their accretion into planetesimals.
Terraria (/ t ə ˈ r ɛər i ə / ⓘ tə-RAIR-ee-ə [1]) is a 2011 action-adventure sandbox game developed by Re-Logic. The game was first released for Windows and has since been ported to other PC and console platforms.