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NGC 7027 has a rich and highly ionized spectrum caused by its hot central star. [7] The progenitor star of NGC 7027 is believed to have been about 3 to 4 times the mass of the Sun before the nebula was formed. [7] It is possible that the central white dwarf of NGC 7027 has an accretion disk that acts as a source of high temperatures. [24]
NGC 6781, also known as the Snowglobe Nebula, [5] is a planetary nebula located in the equatorial constellation of Aquila, about 2.5° east-northeast of the 5th magnitude star 19 Aquilae. [3] It was discovered July 30, 1788 by the Anglo-German astronomer William Herschel. [6] The nebula lies at a distance of 1,500 ly from the Sun. [2]
All planetary nebulae form at the end of the life of a star of intermediate mass, about 1-8 solar masses. It is expected that the Sun will form a planetary nebula at the end of its life cycle. [8] They are relatively short-lived phenomena, lasting perhaps a few tens of millennia, compared to considerably longer phases of stellar evolution. [9]
N44 is classified as an emission nebula because it contains large regions of ionized hydrogen. However, the three strongest emission lines in the nebula are singly ionized oxygen atoms, which emit at an ultraviolet wavelength of 372.7 nm , doubly-ionized oxygen atoms, which emit at a blue-green wavelength of 500.7 nm, and neutral hydrogen atoms ...
IC 11, Sh2-184, [3] Sharpless 184, [1] LBN 616, LBN 123.17-06.28, Pacman Nebula See also: Lists of nebulae NGC 281 , IC 11 or Sh2-184 is a bright emission nebula and part of an H II region in the northern constellation of Cassiopeia and is part of the Milky Way 's Perseus Spiral Arm .
Still other nebulae form as planetary nebulae. This is the final stage of a low-mass star's life, like Earth's Sun. Stars with a mass up to 8–10 solar masses evolve into red giants and slowly lose their outer layers during pulsations in their atmospheres.
The nebula was formed about 70,000 years ago by the star EZ Canis Majoris throwing off its outer hydrogen layers, revealing inner layers of heavier elements. [2] Fast stellar winds, blowing at 1,700 km/s (3.8 million mph) from this star, create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of the star's evolution.
NGC 3132 (also known as the Eight-Burst Nebula, [2] the Southern Ring Nebula, [2] or Caldwell 74) is a bright and extensively studied planetary nebula in the constellation Vela. Its distance from Earth is estimated at 613 pc or 2,000 light-years .