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Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded. According to the nebular theory, stars form in massive and dense clouds of molecular hydrogen—giant molecular clouds (GMC). These clouds are gravitationally unstable, and matter coalesces within them to ...
The Zone of Avoidance (ZOA, ZoA), or Zone of Galactic Obscuration (ZGO), [1] [2] is the area of the sky that is obscured by the Milky Way. [ 3 ] The Zone of Avoidance was originally called the Zone of Few Nebulae in an 1878 paper by English astronomer Richard Proctor that referred to the distribution of " nebulae " in John Herschel 's General ...
Box Nebula NGC 6445: 1786 4.5 11.2 Sagittarius: Eye of Sauron Nebula M 1-42: 10 14 Sagittarius
A nebula that is visible to the human eye from Earth would appear larger, but no brighter, from close by. [6] The Orion Nebula, the brightest nebula in the sky and occupying an area twice the angular diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. [7]
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.
Menzel 1 is a bright planetary nebula that has a prominent central ring of enhanced emission. One model of its structure is a three-dimensional hour-glass shape with a smoothly decreasing density starting from the waist or equator as measured outwardly to the poles. It is radially expanding at a rate of about 23 km/s and estimated to be around ...
The entirety of the Orion Nebula extends across a 1° region of the sky, and includes neutral clouds of gas and dust, associations of stars, ionized volumes of gas, and reflection nebulae. The Nebula is part of a much larger nebula that is known as the Orion molecular cloud complex .
Mz 3 is radially expanding at a rate of about 50 km/s and has its polar axis oriented at an angle of around 30° from the plane of the sky (Lopez & Meaburn 1983; Meaburn & Walsh 1985). It is sometimes compared to the more extensively studied Butterfly Nebula (M 2-9), and it is quite likely that both have a similar evolutionary history. They ...