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Similar nebulae not illuminated by stars do not exhibit visible radiation, but may be detected as opaque clouds blocking light from luminous objects behind them; they are called dark nebulae. [ 25 ] Although these nebulae have different visibility at optical wavelengths, they are all bright sources of infrared emission, chiefly from dust within ...
Abell 35, also known as Sh 2-313, is a nebula located in the constellation of Hydra, at a distance of 400 light years. The nebula is characterised by its unusual appearance, which features a central bow shock surrounded by symmetric emission. [2] In the centre of the nebula lies a binary star, composed of a G-type star and a white dwarf. [3]
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. [40] (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 ...
In many emission nebulae, an entire cluster of young stars is contributing energy. [1] [2] Stars that are hotter than 25,000 K generally emit enough ionizing ultraviolet radiation (wavelength shorter than 91.2 nm) to cause the emission nebulae around them to be brighter than the reflection nebulae. [3]
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.
The cores range in mass from a fraction to several times that of the Sun and are called protostellar (protosolar) nebulae. [2] They possess diameters of 0.01–0.1 pc (2,000–20,000 AU) and a particle number density of roughly 10,000 to 100,000 cm −3. [a] [35] [37] The initial collapse of a solar-mass protostellar nebula takes around 100,000 ...
In astronomy, Bok globules are isolated and relatively small dark nebulae containing dense cosmic dust and gas from which star formation may take place. Bok globules are found within H II regions, and typically have a mass of about two [1] to 50 solar masses contained within a region about a light year or so across (about 4.5 × 10 47 m 3). [2]
NGC 1501 (also known as the Camel's Eye Nebula [3] or the Oyster Nebula [4]) is a complex planetary nebula located in the constellation of Camelopardalis, it was discovered on 27 August 1787 by William Herschel.