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  2. Nebula - Wikipedia

    en.wikipedia.org/wiki/Nebula

    Reflection nebulae themselves do not emit significant amounts of visible light, but are near stars and reflect light from them. [25] Similar nebulae not illuminated by stars do not exhibit visible radiation, but may be detected as opaque clouds blocking light from luminous objects behind them; they are called dark nebulae. [25]

  3. Planetary nebula - Wikipedia

    en.wikipedia.org/wiki/Planetary_nebula

    NGC 6326, a planetary nebula with glowing wisps of outpouring gas that are lit up by a binary [3] central star. A planetary nebula is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. [4] The term "planetary nebula" is a misnomer because they are unrelated to ...

  4. Cosmic dust - Wikipedia

    en.wikipedia.org/wiki/Cosmic_dust

    Cosmic dust – also called extraterrestrial dust, space dust, or star dust – is dust that occurs in outer space or has fallen onto Earth. [ 1 ] [ 2 ] Most cosmic dust particles measure between a few molecules and 0.1 mm (100 μm ), such as micrometeoroids (<30 μm) and meteoroids (>30 μm). [ 3 ]

  5. Nebulae and Star Clusters - Wikipedia

    en.wikipedia.org/wiki/Nebulae_and_Star_Clusters

    Nebulae become visible if the gas glows, or if the cloud reflects starlight or obscures light from more distant objects. The catalogues that it may refer to: Catalogue des nébuleuses et des amas d'étoiles (Messier "M" catalogue) first published 1771; Catalogue of Nebulae and Clusters of Stars (William Herschel 'CN'/"H" catalogue) first ...

  6. Nebular hypothesis - Wikipedia

    en.wikipedia.org/wiki/Nebular_hypothesis

    The cores range in mass from a fraction to several times that of the Sun and are called protostellar (protosolar) nebulae. [2] They possess diameters of 0.01–0.1 pc (2,000–20,000 AU) and a particle number density of roughly 10,000 to 100,000 cm −3. [a] [35] [37] The initial collapse of a solar-mass protostellar nebula takes around 100,000 ...

  7. 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.

  8. Star formation - Wikipedia

    en.wikipedia.org/wiki/Star_formation

    The W51 nebula in Aquila - one of the largest star factories in the Milky Way (August 25, 2020). Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. [1]

  9. Emission nebula - Wikipedia

    en.wikipedia.org/wiki/Emission_nebula

    Planetary nebulae, represented here by the Ring Nebula, are examples of emission nebulae. An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star .