Nebulae Nebulae A Bok globule is a dark cloud of dense dust and gas in which star formation is sometimes taking place. Bok globules are found within H II regions, and typically have a mass of about 10–50 solar masses contained within a region about a light year or so across[1]. They contain molecular hydrogen (H2), carbon oxides and helium, and around 1% (by mass) of silicate dust. Bok globules most commonly result in the formation of double or multiple star systems[2]. ...more on Wikipedia about "Bok globule"
A dark nebula is a large cloud which appears as star-poor regions where the dust of interstellar medium seems to be concentrated. ...more on Wikipedia about "Dark nebula"
In astronomy, diffuse nebulae is the general term for illuminated nebulae. The three types of diffuse nebulae are reflection nebulae, emission nebulae and supernova remnants. They are diffuse as opposed to the non-diffuse dark nebulae. ...more on Wikipedia about "Diffuse nebula"
An emission nebula is a cloud of ionized gas (i.e. a plasma) emitting light of various colors. The most common source for ionization are high-energy photons emitted from a nearby hot star. Among the several different types of emission nebula are H II regions, in which star formation is taking place and young, massive stars are the source of the ionising photons; and planetary nebulae, in which a dying star has thrown off its outer layers, with the exposed hot core then ionizing them. ...more on Wikipedia about "Emission nebula"
An H I region (pronounced "aitch one region") is an interstellar cloud composed of neutral atomic hydrogen (H1). These regions are non-luminous but are detectable because molecules present in small quantities emit radiation in the 21-cm (1,420 MHz) region of the radio-spectrum, even at low temperatures. At ionization fronts, where HI regions collide with expanding ionized gas (such as an H II region), the latter glows brighter than it otherwise would. The degree of ionization in a neutral hydrogen H I region is very small at around 10-4 (ie one particle in 10,000), but plasma physicists consider it to be a weakly ionized plasma. ...more on Wikipedia about "H I region"
An H II region is a cloud of glowing gas and plasma, sometimes several hundred light years across, in which star formation is taking place. Young, hot, blue stars which have formed from the gas emit copious amounts of ultraviolet light, ionising the nebula surrounding them. ...more on Wikipedia about "H II region"
Herbig-Haro objects are small patches of nebulosity associated with newly-born stars, and are formed when gas ejected by young stars collides with clouds of gas and dust nearby at speeds of several hundred kilometres per second. Herbig-Haro objects are ubiquitous in star-forming regions, and several are often seen around a single star, aligned along its rotational axis. ...more on Wikipedia about "Herbig-Haro object"
Interstellar cloud is the generic name given to an accumulation of gas, plasma and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium. Depending on the density, size and temperature of a given cloud, the hydrogen in it can be neutral ( H I regions), ionized ( H II regions) (ie. a plasma), or molecular ( molecular clouds). ...more on Wikipedia about "Interstellar cloud"
A Molecular cloud is a type of interstellar cloud whose density and size permits the formation of molecular hydrogen, H2. ...more on Wikipedia about "Molecular cloud"
A nebula ( Latin: "mist"; pl. nebulae) is an interstellar cloud of dust, gas and plasma. Originally nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive; for example, the Andromeda Galaxy is sometimes referred to as the Andromeda Nebula). ...more on Wikipedia about "Nebula"
A nova remnant is made up of the materials left behind by the gigantic explosion of a star in a nova. It has an expansion velocity of a thousand km/s usually, and has a lifetime of a few centuries. Nova remnants are much less massive than supernova remnants or planetary nebulae. ...more on Wikipedia about "Nova remnant"
A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. They are in fact unrelated to planets; the name originates from a supposed similarity in appearance to giant planets. They are a short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. About 1,500 are known to exist in our galaxy. ...more on Wikipedia about "Planetary nebula"
A plerion (Greek "full") is also called pulsar wind nebula. Plerions have been found inside the shell of supernova remnants. Usually they emit synchrotron radiation powered by a pulsar. A classical example is the Crab Nebula. ...more on Wikipedia about "Plerion"
In astronomy, reflection nebulae are clouds of dust which are simply reflecting the light of a nearby star or stars. The nearby star or stars are not hot enough to cause ionization in the gas of the nebula like in emission nebulae but are bright enough to give sufficient scattering to make the dust visible. Thus, the frequency spectrum shown by reflection nebulae is similar to that of the illuminating stars. Among the microscopic particles responsible for the scattering are carbon compounds (e. g. diamond dust) and compounds of other elements, in particular iron and nickel. The latter two are often aligned with the galactic magnetic field and cause the scattered light to be slightly polarized (Kaler, 1998). The distinction between these two types of nebulae was done by Hubble in 1922. ...more on Wikipedia about "Reflection nebula"
It's real shortopedia feeling!
A stellar nursery is a massive cosmic dust cloud in which microscopic particles may slowly aggregrate due to gravitational attraction and eventually give rise to protostars and subsequently solar systems, with one or more stars and planets. ...more on Wikipedia about "Stellar nursery"
A supernova remnant (SNR) is a plasma made up of the materials left behind by the gigantic explosion of a star in a supernova. There are two possible routes to this end: either a massive star may cease to generate fusion energy in its core, and collapse inward under the force of its own gravity, or a white dwarf star may accumulate material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion. In either case, the resulting supernova explosion expels much or all of the stellar material with great force. This plasma may reach temperatures of 10,000 to 1,000,000 K, and with densities of about 10,000,000 particles per cubic meter. ...more on Wikipedia about "Supernova remnant"
This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia . Direct links to the original articles are in the text.
If you use exact copy or modified of this article you should preserve above paragraph and put also : It uses material from
the Shortopedia article about "Nebulae".
| MAIN PAGE | MAIN INDEX | CONTACT US |