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The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting the Sun which clumped up together to form the planets.
A major difficulty was that, in this supposition, turbulent dissipation took place over the course of a single millennium, which did not give enough time for planets to form. The nebular hypothesis was first proposed in 1734 by Swedish scientist Emanuel Swedenborg [6] and later expanded upon by Prussian philosopher Immanuel Kant in 1755.
The first planetary nebula discovered (though not yet termed as such) was the Dumbbell Nebula in the constellation of Vulpecula.It was observed by Charles Messier on July 12, 1764 and listed as M27 in his catalogue of nebulous objects. [10]
Objects named nebulae belong to four major groups. Before their nature was understood, galaxies ("spiral nebulae") and star clusters too distant to be resolved as stars were also classified as nebulae, but no longer are. H II regions, large diffuse nebulae containing ionized hydrogen; Planetary nebulae; Supernova remnants (e.g., Crab Nebula ...
1968 – Kenneth Nordtvedt studies a possible violation of the weak equivalence principle for self-gravitating bodies and proposes a new test of the weak equivalence principle based on observing the relative motion of the Earth and Moon in the Sun's gravitational field. [162] 1969 – William B. Bonnor introduces the Bonnor beam. [163]
The Eagle Nebula (catalogued as Messier 16 or M16, and as NGC 6611, and also known as the Star Queen Nebula) is a young open cluster of stars in the constellation Serpens, discovered by Jean-Philippe de Cheseaux in 1745–46.
It was proposed as a replacement for the Laplacian version of the nebular hypothesis that had prevailed since the 19th century. The hypothesis was based on the idea that a star passed close enough to the sun early in its life to cause tidal bulges to form on its surface, which along with the internal process that leads to solar prominences ...
The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus.The common name comes from a drawing that somewhat resembled a crab with arms produced by William Parsons, 3rd Earl of Rosse, in 1842 or 1843 using a 36-inch (91 cm) telescope. [6]