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The number of nebulae was then greatly increased by the efforts of William Herschel and his sister, Caroline Herschel. Their Catalogue of One Thousand New Nebulae and Clusters of Stars [16] was published in 1786. A second catalog of a thousand was published in 1789, and the third and final catalog of 510 appeared in 1802.
Spiral nebula surrounding NGC 262, which is one of the largest known galaxies. Ivory Nebula: 1,190,500 ly (365,000 pc) [2] Enormous Lyα nebula (ELAN) Also called MLAN1 at z=2.31. Another ELAN, called MLAN 10 is nearby. Q0042−2627 nebula 1,040,000 ly (320,000 pc) [10] Enormous Lyα nebula (ELAN) Around the quasar LBQS 0042-2627, at z=3.280
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 .
The Veil Nebula is a cloud of heated and ionized gas and dust in the constellation Cygnus. [4]It constitutes the visible portions of the Cygnus Loop, [5] a supernova remnant, many portions of which have acquired their own individual names and catalogue identifiers.
A typical planetary nebula is roughly one light year across, and consists of extremely rarefied gas, with a density generally from 100 to 10,000 particles per cm 3. [42] (The Earth's atmosphere, by comparison, contains 2.5 × 10 19 particles per cm 3.) Young planetary nebulae have the highest densities, sometimes as high as 10 6 particles per ...
Reflection nebula are usually blue because the scattering is more efficient for blue light than red (this is the same scattering process that gives us blue skies and red sunsets). Reflection nebulae and emission nebulae are often seen together and are sometimes both referred to as diffuse nebulae. Some 500 reflection nebulae are known.
The Horsehead Nebula (also known as Barnard 33 or B33) is a small dark nebula in the constellation Orion. [2] The nebula is located just to the south of Alnitak , the easternmost star of Orion's Belt , and is part of the much larger Orion molecular cloud complex .
In 1852 Stephen Alexander supposed that Milky Way is also a spiral nebula. [35] The question of whether such objects were separate galaxies independent of the Milky Way, or a type of nebula existing within our own galaxy, was the subject of the Great Debate of 1920, between Heber Curtis of Lick Observatory and Harlow Shapley of Mount Wilson ...