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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.
Nova remnants when compared to supernova remnants or planetary nebulae generate much less both in energy and mass. They can be observed for perhaps a few centuries. [ 1 ] Notably, more nova remnants have been found with the new novae, due to improved imaging technology like CCD and at other wavelengths.
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 .
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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.
Artist's conception of a white dwarf, right, accreting hydrogen from the Roche lobe of its larger companion star A nova (pl. novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", Latin for "new") that slowly fades over weeks or months.
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This effect was observed for light from the Crab Nebula by Martin, Illing and Angel. [19] An optically thick circumstellar environment can potentially produce much larger CP than the interstellar medium. Martin [18] suggested that LP light can become CP near a star by multiple scattering in an optically thick asymmetric circumstellar dust cloud.