"pyrimidine, found in meteorites. Pyrimidine, like polycyclic aromatic hydrocarbons (PAHs), the most carbon-rich chemical found in the Universe, may have been formed in red giants or in interstellar dust and gas clouds, according to the scientists. The Solar System has its own interplanetary dust cloud, as do extrasolar systems. There are different types of nebulae with different physical causes and processes: diffuse nebula, infrared (IR) reflection nebula, supernova remnant, molecular cloud, HII regions, photodissociation regions, and dark nebula. Distinctions between those types of nebula are that different radiation processes are at work. For example, H II regions, like the Orion"
"Nebula A nebula (Latin for ""cloud"" or ""fog""; pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, the term was used to describe any diffuse astronomical object, including galaxies beyond the Milky Way. The Andromeda Galaxy, for instance, was once referred to as the ""Andromeda Nebula"" (and spiral galaxies in general as ""spiral nebulae"") before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble and others. Most nebulae are of vast size; some are hundreds of light years in diameter. A nebula that"
"Interstellar cloud An interstellar cloud is generally 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, (ISM), the matter and radiation that exists in the space between the star systems in a galaxy. Depending on the density, size, and temperature of a given cloud, its hydrogen can be neutral, making an H I region; ionized, or plasma making it an H II region; or molecular, which are referred to simply as molecular clouds, or sometimetimes dense clouds. Neutral and ionized clouds are sometimes also"
"Cloud In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture (usually in the form of water vapor) from an adjacent source to raise the dew point to the ambient temperature. They are seen in the Earth's homosphere (which includes the troposphere, stratosphere,"
"Interplanetary dust cloud The interplanetary dust cloud, or zodiacal cloud, consists of cosmic dust (small particles floating in outer space) that pervades the space between planets within planetary systems such as the Solar System. This system of particles has been studied for many years in order to understand its nature, origin, and relationship to larger bodies. In our Solar System, the interplanetary dust particles have a role in scattering sunlight and in emitting thermal radiation, which is the most prominent feature of the night sky's radiation with wavelengths ranging 5–50 μm. The particle sizes of grains characterizing the infrared emission"
"metallicity is needed. High-velocity clouds are identified with an HVC prefix, as with HVC 127-41-330. Interstellar cloud An interstellar cloud is generally 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, (ISM), the matter and radiation that exists in the space between the star systems in a galaxy. Depending on the density, size, and temperature of a given cloud, its hydrogen can be neutral, making an H I region; ionized, or plasma making it an H II region; or molecular, which are referred to"
"Cosmic dust Cosmic dust, also called extraterrestrial dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles are between a few molecules to 0.1 µm in size. Cosmic dust can be further distinguished by its astronomical location: intergalactic dust, interstellar dust, interplanetary dust (such as in the zodiacal cloud) and circumplanetary dust (such as in a planetary ring). In the Solar System, interplanetary dust causes the zodiacal light. Solar System dust includes comet dust, asteroidal dust, dust from the Kuiper belt, and interstellar dust passing through the Solar System. Thousands"
"They range from a few light years to dozens of light years across. While they are not technically cirrus clouds, the dust clouds are referred to as ""cirrus"" because of their similarity to the clouds on Earth. They also emit infrared radiation, similar to the way cirrus clouds on Earth reflect heat being radiated out into space. Footnotes Bibliography Cirrus cloud Cirrus (cloud classification symbol: Ci) is a genus of atmospheric cloud generally characterized by thin, wispy strands, giving the type its name from the Latin word ""cirrus"", meaning a ringlet or curling lock of hair. This cloud can form"
"called ""diffuse clouds"". An interstellar cloud is formed by the gas and dust particles from a red giant in its later life. The chemical composition of interstellar clouds is determined by studying electromagnetic radiation or EM radiation that they emanate, and we receive – from radio waves through visible light, to gamma rays on the electromagnetic spectrum – that we receive from them. Large radio telescopes scan the intensity in the sky of particular frequencies of electromagnetic radiation which are characteristic of certain molecules' spectra. Some interstellar clouds are cold and tend to give out EM radiation of large wavelengths."
"Veil Nebula The Veil Nebula is a cloud of heated and ionized gas and dust in the constellation Cygnus. It constitutes the visible portions of the Cygnus Loop, a supernova remnant, many portions of which have acquired their own individual names and catalogue identifiers. The source supernova was a star 20 times more massive than the Sun, which exploded around 8,000 years ago. The remnants have since expanded to cover an area of the sky roughly 3 degrees in diameter (about 6 times the diameter, or 36 times the area, of the full Moon). The distance to the nebula is"
"much of the optical and X-ray emission from supernova remnants originates from ionized gas, a great amount of the radio emission is a form of non-thermal emission called synchrotron emission. This emission originates from high-velocity electrons oscillating within magnetic fields. Nebula A nebula (Latin for ""cloud"" or ""fog""; pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, the term was used to describe any diffuse astronomical object, including galaxies beyond the Milky Way. The Andromeda Galaxy, for instance, was once referred to as the ""Andromeda Nebula"" (and spiral galaxies in general"
"this assumption in observations of some other galaxies. Within molecular clouds are regions with higher density, where lots of dust and gas cores reside, called clumps. These clumps are the beginning of star formation, if gravity can overcome the high density and force the dust and gas to collapse. Within the Milky Way, molecular gas clouds account for less than one percent of the volume of the interstellar medium (ISM), yet it is also the densest part of the medium, comprising roughly half of the total gas mass interior to the Sun's galactic orbit. The bulk of the molecular gas"
"found within these lanes, mix together and combine to form stars and planets. Dust lane A dust lane is a relatively dense obscuring band of interstellar dust, observed as a dark swath against the background of a brighter object, especially a galaxy. These dust lanes can usually be seen in spiral galaxies (e.g., the Milky Way) when viewed from the edge. Due to the dense and relatively thick nature of this dust, light from the galaxy is reduced by several magnitudes. In the Milky Way, this reduction of light makes it impossible to see the light from the central bulge"
"Intergalactic dust Intergalactic dust is cosmic dust in between galaxies in intergalactic space. Evidence for intergalactic dust has been suggested as early as 1949, and study of it grew throughout the late 20th century. There are large variations in the distribution of intergalactic dust. The dust may affect intergalactic distance measurements, such as to supernova and quasars in other galaxies. Intergalactic dust can form intergalactic dust clouds, known to exist around some galaxies since the 1960s. By the 1980s, at least four intergalactic dust clouds had been discovered within several megaparsec (Mpc) of the Milky Way galaxy, exemplified by the"
"""Pioneer 10"", ""Pioneer 11"", ""Ulysses"" (heliocentric orbit out to the distance of Jupiter), ""Galileo"" (Jupiter Orbiter), ""Cassini"" (Saturn orbiter), and ""New Horizons"" (see Venetia Burney Student Dust Counter). Interplanetary dust cloud The interplanetary dust cloud, or zodiacal cloud, consists of cosmic dust (small particles floating in outer space) that pervades the space between planets within planetary systems such as the Solar System. This system of particles has been studied for many years in order to understand its nature, origin, and relationship to larger bodies. In our Solar System, the interplanetary dust particles have a role in scattering sunlight and in"
"a dense plume of particles. The ash density and constant motion within the volcanic plume produces charge by frictional interactions (triboelectrification), resulting in very powerful and very frequent flashes as the cloud attempts to neutralize itself. Due to the extensive solid material (ash) content, unlike the water rich charge generating zones of a normal thundercloud, it is often called a dirty thunderstorm. Lightning has been observed within the atmospheres of other planets, such as Jupiter and Saturn. Although in the minority on Earth, superbolts appear to be common on Jupiter. Lightning on Venus has been a controversial subject after decades"
"of two smaller galaxies that were rotating in opposite directions to each other. Bright stars in galaxies can also help determine the distance to a galaxy, which may be a more accurate method than parallax or standard candles. The interstellar medium is matter that occupies the space between star systems in a galaxy. 99% of this matter is gaseous - hydrogen, helium, and smaller quantities of other ionized elements such as oxygen. The other 1% is dust particles, thought to be mainly graphite, silicates, and ices. Clouds of the dust and gas are referred to as nebulae. There are three"
"matter may appear in. In the outer Solar System, hydrogen and helium are referred to as ""gases""; water, methane, and ammonia as ""ices""; and silicates and metals as ""rock"". Because Uranus and Neptune are primarily composed of, in this terminology, ices, not gas, they are increasingly referred to as ice giants and separated from the gas giants. Gas giants can, theoretically, be divided into five distinct classes according to their modeled physical atmospheric properties, and hence their appearance: ammonia clouds (I), water clouds (II), cloudless (III), alkali-metal clouds (IV), and silicate clouds (V). Jupiter and Saturn are both class I."
"Smith's Cloud Smith's Cloud is a high-velocity cloud of hydrogen gas located in the constellation Aquila at Galactic coordinates ""l"" = 39°, ""b"" = −13°. The cloud was discovered in 1963 by Gail Bieger, ""née"" Smith, who was an astronomy student at Leiden University in the Netherlands. Using the National Science Foundation's Robert C. Byrd Green Bank Telescope, radio astronomers have found that Smith's cloud has a mass of at least one million solar masses and measures long by wide in projection. The cloud is between and from Earth and has an angular diameter of 10 to 12 degrees, approximately"
"Dust lane A dust lane is a relatively dense obscuring band of interstellar dust, observed as a dark swath against the background of a brighter object, especially a galaxy. These dust lanes can usually be seen in spiral galaxies (e.g., the Milky Way) when viewed from the edge. Due to the dense and relatively thick nature of this dust, light from the galaxy is reduced by several magnitudes. In the Milky Way, this reduction of light makes it impossible to see the light from the central bulge of the galaxy from Earth. This dust, as well as the gasses also"
"Oort cloud The Oort cloud (), named after the Dutch astronomer Jan Oort, sometimes called the Öpik–Oort cloud, is a theoretical cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years). It is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud. Both regions lie beyond the heliosphere and in interstellar space. The Kuiper belt and the scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth as far from the Sun as the Oort"
"astronomy. Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, CO (CO with oxygen as the O isotope), CS, NH (ammonia), HCO (formaldehyde), c-CH (cyclopropenylidene) and a molecular ion NH (diazenylium), all of which are relatively transparent. These clouds are the spawning grounds of stars and planets, and understanding their development is essential to understanding star formation. The form of such dark clouds is very irregular: they have no clearly defined outer boundaries and sometimes take"
"Cosmic wind Cosmic wind is a powerful cosmic force that can push interstellar dust clouds of low density into intergalactic space. Although it easily pushes low density gas and dust clouds, it can not easily push high density clouds. As the cosmic winds start to push the clouds, they start to separate and start looking like taffy being pulled apart. It has a primary composition of photons ejected from large stars and sometimes thermal energy from exploding stars. It can be caused by orbital motion of gas in the cluster of a galaxy, or can be ejected from a black"
"400–450 light years distant in the ρ Ophiuchi cloud complex. A more compact site of star formation is the opaque clouds of dense gas and dust known as Bok globules, so named after the astronomer Bart Bok. These can form in association with collapsing molecular clouds or possibly independently. The Bok globules are typically up to a light year across and contain a few solar masses. They can be observed as dark clouds silhouetted against bright emission nebulae or background stars. Over half the known Bok globules have been found to contain newly forming stars. An interstellar cloud of gas"
"Fog Fog is a visible aerosol consisting of minute water droplets or ice crystals suspended in the air at or near the Earth's surface. Although it has no Latin name, fog can be considered a type of low-lying cloud, usually resembling stratus, and is heavily influenced by nearby bodies of water, topography, and wind conditions. In turn, fog has affected many human activities, such as shipping, travel, and warfare. The term ""fog"" is typically distinguished from the more generic term ""cloud"" in that fog is low-lying, and the moisture in the fog is often generated locally (such as from a"
"Perseus molecular cloud The Perseus molecular cloud (Per MCld) is a nearby (600 ly) giant molecular cloud in the constellation of Perseus and contains over 10,000 solar masses of gas and dust covering an area of 6 by 2 degrees. Unlike the Orion molecular cloud it is almost invisible apart from two clusters, IC 348 and NGC 1333, where low-mass stars are formed. It is very bright at mid and far-infrared wavelengths and in the submillimeter originating in dust heated by the newly formed low-mass stars. It shows a curious ring structure in maps made by the IRAS and MSX"
"more ""end on"" than ""side on"". The Keyhole, or Keyhole Nebula, is a small dark cloud of cold molecules and dust within the Carina Nebula, containing bright filaments of hot, fluorescing gas, silhouetted against the much brighter background nebula. John Herschel used the term ""lemniscate-oval vacuity"" when first describing it, and subsequently referred to it simply as the ""oval vacuity"". The term lemniscate continued to be used to describe this portion of the nebula until popular astronomy writer Emma Converse described the shape of the nebula as ""resembling a keyhole"" in an 1873 ""Appleton's Journal"" article. The name Keyhole Nebula"
"space, observed by the Infrared Space Observatory and the Spitzer Space Telescope, has made it clear that carbon-containing molecules are ubiquitous in space. These include polycyclic aromatic hydrocarbons (PAHs), fullerenes and diamondoids (hydrocarbons that have the same crystal structure as diamond). If dust in space has a similar concentration, a gram of it would carry up to 10 quadrillion of them, but so far there is little evidence for their presence in the interstellar medium; they are difficult to tell apart from diamondoids. A 2014 study led by James Kennett at the University of California Santa Barbara identified a thin"
"hole. Because new stars and planets form from gases, the cosmic winds that push the gases away are preventing new stars from forming. Cosmic wind Cosmic wind is a powerful cosmic force that can push interstellar dust clouds of low density into intergalactic space. Although it easily pushes low density gas and dust clouds, it can not easily push high density clouds. As the cosmic winds start to push the clouds, they start to separate and start looking like taffy being pulled apart. It has a primary composition of photons ejected from large stars and sometimes thermal energy from exploding"
"Molecular cloud A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit the formation of molecules, most commonly molecular hydrogen (H). This is in contrast to other areas of the interstellar medium that contain predominantly ionized gas. Molecular hydrogen is difficult to detect by infrared and radio observations, so the molecule most often used to determine the presence of H is carbon monoxide (CO). The ratio between CO luminosity and H mass is thought to be constant, although there are reasons to doubt"
"Diamond dust Diamond dust is a ground-level cloud composed of tiny ice crystals. This meteorological phenomenon is also referred to simply as ""ice crystals"" and is reported in the METAR code as IC. Diamond dust generally forms under otherwise clear or nearly clear skies, so it is sometimes referred to as clear-sky precipitation. Diamond dust is most commonly observed in Antarctica and the Arctic, but can occur anywhere with a temperature well below freezing. In the polar regions of Earth, diamond dust may persist for several days without interruption. Diamond dust is similar to fog in that it is a"
"satellites and the Spitzer Space Telescope and has recently detected by the COSMOSOMAS at microwave frequencies as a source of anomalous ""spinning dust"" emission. Perseus molecular cloud The Perseus molecular cloud (Per MCld) is a nearby (600 ly) giant molecular cloud in the constellation of Perseus and contains over 10,000 solar masses of gas and dust covering an area of 6 by 2 degrees. Unlike the Orion molecular cloud it is almost invisible apart from two clusters, IC 348 and NGC 1333, where low-mass stars are formed. It is very bright at mid and far-infrared wavelengths and in the submillimeter"
"mostly emitted by dust. Wreath Nebula The Wreath Nebula (also known as Barnard 3 or IRAS Ring G159.6-18.5 is an emission nebula and H II region with a radius of about 22 light-years, located about 1,000 light-years away within our Milky Way galaxy in the Perseus Molecular Cloud complex, near the boundary with the constellation of Taurus. Interstellar clouds like these are stellar nurseries, places where baby stars are being born. The green ring (evergreen) is made of tiny particles of warm dust whose composition is very similar to smog found here on Earth. The red cloud (bow) in the"