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  2. Nebula - Wikipedia

    en.wikipedia.org/wiki/Nebula

    The Carina Nebula is an example of a diffuse nebula. Most nebulae can be described as diffuse nebulae, which means that they are extended and contain no well-defined boundaries. [24] Diffuse nebulae can be divided into emission nebulae, reflection nebulae and dark nebulae.

  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. Herbig–Haro object - Wikipedia

    en.wikipedia.org/wiki/Herbig–Haro_object

    Both George Herbig and Guillermo Haro made independent observations of several of these objects in the Orion Nebula during the 1940s. Herbig also looked at Burnham's Nebula and found it displayed an unusual electromagnetic spectrum, with prominent emission lines of hydrogen, sulfur and oxygen. Haro found that all the objects of this type were ...

  5. Bipolar nebula - Wikipedia

    en.wikipedia.org/wiki/Bipolar_nebula

    2 Examples. 3 References. ... Download as PDF; Printable version; In other projects ... A bipolar nebula is a type of nebula characterized by two lobes either side of ...

  6. Angular diameter - Wikipedia

    en.wikipedia.org/wiki/Angular_diameter

    Carina Nebula: 2° by 2° Note: brightest nebula in the night sky, 1.0 apparent magnitude (V) North America Nebula: 2° by 100 ′ Earth in the Moon's sky: 2° - 1°48 ′ [12] Appearing about three to four times larger than the Moon in Earth's sky The Sun in the sky of Mercury: 1.15° - 1.76° [13] Orion Nebula: 1°5 ′ by 1°

  7. Cometary knot - Wikipedia

    en.wikipedia.org/wiki/Cometary_knot

    [1] [2] They are believed to be a common feature of the evolution of planetary nebulae, but can only be resolved in the nearest examples. [2] They are generally larger than the size of the Solar System (i.e. the orbit of Pluto ), with masses of around 0.00001 times the mass of the Sun , which is comparable to the mass of the Earth .

  8. Nebular hypothesis - Wikipedia

    en.wikipedia.org/wiki/Nebular_hypothesis

    A protoplanetary disk forming in the Orion Nebula. The main problem in the physics of accretion disks is the generation of turbulence and the mechanism responsible for the high effective viscosity. [2] The turbulent viscosity is thought to be responsible for the transport of the mass to the central protostar and momentum to the periphery of the ...

  9. Stellar-wind bubble - Wikipedia

    en.wikipedia.org/wiki/Stellar-wind_bubble

    The Bubble Nebula (NGC 7635), imaged by the Hubble Space Telescope, is seven light years across. A stellar-wind bubble is a cavity light-years across filled with hot gas blown into the interstellar medium by the high-velocity (several thousand km/s) stellar wind from a single massive star of type O or B.