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A-type star In the Harvard spectral classification system, a class of main-sequence star having spectra dominated by Balmer absorption lines of hydrogen. Stars of spectral class A are typically blue-white or white in color, measure between 1.4 and 2.1 times the mass of the Sun, and have surface temperatures of 7,600–10,000 kelvin.
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.
The nebula's color depends on its chemical composition and degree of ionization. Due to the prevalence of hydrogen in interstellar gas, and its relatively low energy of ionization, many emission nebulae appear red due to strong emissions of the Balmer series. If more energy is available, other elements will be ionized, and green and blue ...
The Kelvin–Helmholtz mechanism is an astronomical process that occurs when the surface of a star or a planet cools. The cooling causes the internal pressure to drop, and the star or planet shrinks as a result.
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 .
A similar effect, known as the magnetic draping effect, occurs when a super-Alfvénic plasma flow impacts an unmagnetized object such as what happens when the solar wind reaches the ionosphere of Venus: [20] the flow deflects around the object draping the magnetic field along the wake flow.
SN 1054 remnant (Crab Nebula).. A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova.The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.
It is a type of stellar explosion that ejects material with an unusually high kinetic energy, an order of magnitude higher than most supernovae, with a luminosity at least 10 times greater. Hypernovae release such intense gamma rays that they often appear similar to a type Ic supernova , but with unusually broad spectral lines indicating an ...