Porous chondrite interplanetary dust particle. Courtesy of E. K. Jessberger, Institut für Planetologie, Münster, Germany, and Don Brownlee, University of Washington, Seattle, under a cc-a-2. 5 license.

Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0. Dust is a general name for minute Solid particles with Diameters less than 500 micrometers. In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by 1 mm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust, circumplanetary dust, dust clouds around other stars, and the major interplanetary dust components to our own zodiacal dust complex (seen in visible light as the zodiacal light): Comet dust, asteroidal dust plus some of the less significant contributors: Kuiper belt dust, interstellar dust passing through our solar system, and beta meteoroids. The interplanetary dust cloud is Cosmic dust (small particles floating in space which pervade the space between Planets in the Solar System and in The zodiacal light is a faint roughly triangular whitish glow seen in the night sky which appears to extend up from the vicinity of the Sun along the Ecliptic Comet dust refers to Cosmic dust that originates from a Comet. The Kuiper belt (ˈkaɪpɚ to rhyme with "viper" sometimes called the Edgeworth-Kuiper belt, is a region of the Solar System beyond the planets extending

Cosmic dust was once solely an annoyance to astronomers, as it obscures objects they wish to observe. When infrared astronomy began, those so-called annoying dust particles were observed to be significant and vital components of astrophysical processes. Infrared astronomy is the branch of Astronomy and Astrophysics which deals with objects visible in Infrared (IR radiation

For example, Cosmic Dust can drive the mass loss when a star is nearing the end of its life, play a part in the early stages of star formation, and form planets. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime Star Formation is the process by which dense parts of Molecular clouds collapse into a ball of plasma to form a Star. A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is In our own solar system, dust plays a major role in the zodiacal light, Saturn's B Ring spokes, the outer diffuse planetary rings at Jupiter, Saturn, Uranus and Neptune, the resonant dust ring at the Earth, and comets. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. The zodiacal light is a faint roughly triangular whitish glow seen in the night sky which appears to extend up from the vicinity of the Sun along the Ecliptic Saturn has the most extensive Planetary ring system of any planet in the Solar System. A planetary ring is a ring of Cosmic dust and other small particles Orbiting around a Planet in a flat disc-shaped region Neptune ( English|AmE] ] is the eighth and farthest Planet from the Sun in the Solar System. A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail —

The study of dust is a many-faceted research topic that brings together different scientific fields: physics (solid-state, electromagnetic theory, surface physics, statistical physics, thermal physics), (fractal mathematics), chemistry (chemical reactions on grain surfaces), meteoritics, as well as every branch of astronomy and astrophysics. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Solid-state physics, the largest branch of Condensed matter physics, is the study of rigid Matter, or Solids The bulk of solid-state physics theory and Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of Statistical physics is one of the fundamental theories of Physics, and uses methods of Statistics in solving physical problems Thermal physics is the combined study of Thermodynamics, Statistical mechanics, and Kinetic theory. A fractal is generally "a rough or fragmented geometric shape that can be split into parts each of which is (at least approximately a reduced-size copy of the whole" A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called Meteoritics is a science that deals with Meteorites and other extraterrestrial materials that further our understanding of the origin and history of the solar system Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study Astrophysics is the branch of Astronomy that deals with the Physics of the Universe, including the physical properties ( Luminosity, ^[1] These disparate research areas can be linked by the following theme: the cosmic dust particles evolve cyclically; chemically, physically and dynamically. The evolution of dust traces out paths in which the universe recycles material, in processes analogous to the daily recycling steps with which many people are familiar: production, storage, processing, collection, consumption, and discarding. Observations and measurements of cosmic dust in different regions provide an important insight into the universe's recycling processes; in the clouds of the diffuse interstellar medium, in molecular clouds, in the circumstellar dust of young stellar objects, and in planetary systems such as our own solar system, where astronomers consider dust as in its most recycled state. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar Young stellar object (YSO denotes a star in its early stage of evolution The Solar System consists of the Sun and those celestial objects bound to it by Gravity. The astronomers accumulate observational ‘snapshots’ of dust at different stages of its life and, over time, form a more complete movie of the universe's complicated recycling steps.

The detection of cosmic dust points to another facet of cosmic dust research: dust acting as photons. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Once cosmic dust is detected, the scientific problem to be solved is an inverse problem to determine what processes brought that encoded photon-like object (dust) to the detector. An inverse problem is the task that often occurs in many branches of Science and Mathematics where the values of some model parameter(s must be obtained from the Parameters such the particle's initial motion, material properties, intervening plasma and magnetic field determined the dust particle's arrival at the dust detector. In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges Slightly changing any of these parameters can give significantly different dust dynamical behavior. Therefore one can learn about where that object came from, and what is (in) the intervening medium.

Detection methods

Cosmic dust can be detected by indirect methods utilizing the radiative properties of cosmic dust. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter.

Cosmic dust can also be detected directly ('in-situ') using a variety of collection methods and from a variety of collection locations. At the Earth, generally, an average of 40 tons per day of extraterrestrial material falls to the Earth^[2]. The Earth-falling dust particles are collected in the Earth's atmosphere using plate collectors under the wings of stratospheric-flying NASA airplanes and collected from surface deposits on the large Earth ice-masses (Antarctica and Greenland / the Arctic) and in deep-sea sediments. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program Overview Fixed-wing aircraft range from small training and recreational aircraft to Wide-body aircraft and military cargo aircraft. Don Brownlee at the University of Washington in Seattle first reliably identified the extraterrestrial nature of collected dust particles in the later 1970s. Another source is the meteorites, which contain stardust extracted from them (see below). Stardust grains are solid refractory pieces of individual presolar stars. They are recognized by their extreme isotopic compositions, which can only be isotopic compositions within evolved stars, prior to any mixing with the interstellar medium. These grains condensed from the stellar matter as it cooled while leaving the star.

In interplanetary space, dust detectors on planetary spacecraft have been built and flown , some are presently flying, and more are presently being built to fly. The large orbital velocities of dust particles in interplanetary space (typically 10-40 km/s) make intact particle capture problematic. Instead, in-situ dust detectors are generally devised to measure parameters associated with the high-velocity impact of dust particles on the instrument, and then derive physical properties of the particles (usually mass and velocity) through laboratory calibration (i. e. impacting accelerated particles with known properties onto a laboratory replica of the dust detector). Over the years dust detectors have measured, among others, the impact light flash, acoustic signal and impact ionisation. Recently the dust instrument on Stardust captured particles intact in low-density aerogel. Stardust is an American interplanetary mission of the NASA Jet Propulsion Laboratory, whose primary purpose was to investigate the makeup of the

Dust detectors in the past flew on the HEOS-2, Helios, Pioneer 10, Pioneer 11, Giotto, and Galileo space missions, on the Earth-orbiting LDEF, EURECA, and Gorid satellites, and some scientists have utilized the Voyager 1,2 spacecraft as giant Langmuir probes to directly sample the cosmic dust. In Greek mythology the Sun was personified as Helios (ˈhiliˌɑs ( Ἥλιος Latinized as Helius) Pioneer 10 ( Pioneer-F) was the first Spacecraft to travel through the Asteroid belt, which it entered on July 15, 1972 Pioneer 11 was the second mission (after its sister probe Pioneer 10) to investigate Jupiter and the Outer solar system and the first to explore the planet Giotto was a European Robotic spacecraft mission from the European Space Agency, intended to fly by and study Halley's Comet. Galileo was an Unmanned spacecraft sent by NASA to study the Planet Jupiter and its moons Named after the Astronomer NASA 's Long Duration Exposure Facility, or LDEF, was a School bus -sized cylindrical space experiment rack that exposed various material samples to See also Voyager 1 and Voyager 2. The Voyager program consists of a pair of unmanned scientific probes Voyager 1 and A Langmuir probe is a device named after Nobel Prize winning physicist Irving Langmuir, used to determine the electron temperature electron density and electric Presently dust detectors are flying on the Ulysses, Cassini, Proba, Rosetta, Stardust, and the New Horizons spacecraft. Ulysses is a robotic Space probe designed to study the Sun at all latitudes Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its Rosetta is a European Space Agency -led Robotic spacecraft mission launched in 2004 intended to study the comet 67P/Churyumov-Gerasimenko. Stardust is an American interplanetary mission of the NASA Jet Propulsion Laboratory, whose primary purpose was to investigate the makeup of the New Horizons is a Robotic spacecraft mission by NASA currently underway The collected dust at Earth or collected further in space and returned by sample-return space missions is then analyzed by dust scientists in their respective laboratories all over the world. One large storage facility for cosmic dust exists at the NASA Houston JSC.

Infrared light can penetrate the cosmic dust clouds, allowing us to peer into regions of star formation and the centers of galaxies. NASA's Spitzer Space Telescope is the largest infrared telescope ever launched into space. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The Spitzer Space Telescope (formerly SIRTF, the Space Infrared Telescope Facility) was launched into space by a Delta rocket from Cape Canaveral, Florida on 25 August 2003. During its mission, Spitzer will obtain images and spectra by detecting the infrared energy, or heat, radiated by objects in space between wavelengths of 3 and 180 micrometres. Most of this infrared radiation is blocked by the Earth's atmosphere and cannot be observed from the ground. The findings from the Spitzer already revitalized the studies of cosmic dust. A recent report from a Spitzer team shows some evidence that cosmic dust is formed near a supermassive black hole.

Radiative properties of cosmic dust

A dust particle interacts with electromagnetic radiation in a way that depends on its cross section, the wavelength of the electromagnetic radiation, and on the nature of the grain: its refractive index, size, etc. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Geometry, a cross section is the intersection of a body in 2-dimensional space with a line or of a body in 3-dimensional space with a plane etc In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium The radiation process for an individual grain is called its emissivity, dependent on the grain's efficiency factor. The emissivity of a material (usually written \epsilon is the ratio of energy radiated by a particular material to energy radiated by a Black body at Furthermore, we have to specify whether the emissivity process is extinction, scattering, or absorption. Extinction is a term used in Astronomy to describe the absorption and Scattering of Electromagnetic radiation emitted by Astronomical objects Scattering is a general physical process whereby some forms of Radiation, such as Light, Sound or moving particles for example are forced to deviate from In the radiation emission curves, several important signatures identify the composition of the emitting or absorbing dust particles.

Dust particles can scatter light nonuniformly. Forward-scattered light means that light is redirected slightly by diffraction off its path from the star/sunlight, and back-scattered light is reflected light. Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle

The scattering and extinction ("dimming") of the radiation gives useful information about the dust grain sizes. For example, if the object(s) in one's data is many times brighter in forward-scattered visible light than in back-scattered visible light, then we know that a significant fraction of the particles are about a micrometer in diameter.

The scattering of light from dust grains in long exposure visible photographs is quite noticeable in reflection nebulas, and gives clues about the individual particle's light-scattering properties. In Astronomy, reflection nebulae are clouds of dust which are simply reflecting the light of a nearby Star or stars In x-ray wavelengths, many scientists are investigating the scattering of x-rays by interstellar dust, and some have suggested that astronomical x-ray sources would possess diffuse haloes, due to the dust.

Stardust

Stardust grains (see also presolar grains) are contained within meteorites, from which they are extracted in terrestrial laboratories. Presolar grains are isotopically-distinct clusters of material found in the fine-grained matrix of primitive Meteorites, whose differences from the surrounding meteorite So-called carbonaceous chondrites are especially fertile reservoirs of stardust. A carbonaceous chondrite or a C-type chondrite is a type of chondritic Meteorite which contains high levels of Water and Organic compounds Each stardust grain existed before the earth was formed. The meteorites have preserved the previously interstellar stardust grains since that time. Stardust is a scientific term rather than a poetic one, referring to refractory dust grains that condensed from cooling ejected gases from individual presolar stars. Many different types of stardust have been identified by laboratory measurements of the highly unusual isotopic composition of the chemical elements that comprise each stardust grain. Many new aspects of nucleosynthesis have been discovered from those isotopic ratios ^[3]. Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons The following website http://www.dtm.ciw.edu/lrn/psg_main.html contains an excellent introduction to, and photographs of, many differing types of stardust. An important property of stardust is the hard, refractory, high-temperature nature of the grains. Prominent are silicon carbide, graphite, aluminum oxide, aluminum spinel, and other such grains that would condense at high temperature from a cooling gas, such as in stellar winds or in the decompression of the inside of a supernova. Silicon carbide ( is a compound of Silicon and Carbon bonded together to form Ceramics but it also occurs in nature as the extremely rare mineral The Mineral graphite, as with Diamond and Fullerene, is one of the Allotropes of carbon. A supernova (plural supernovae or supernovas) is a stellar Explosion. They differ greatly from the solids formed at low temperature within the interstellar medium. Also important are their extreme isotopic compositions, which are expected to exist nowhere in the interstellar medium. This also suggests that the stardust condensed from the gases of individual stars before the isotopes could be diluted by mixing with the interstellar medium. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides These allow the source stars to be identified. For example, the heavy elements within the SiC grains are almost pure s process isotopes, fitting their condensation within AGB star red giant winds inasmuch as the AGB stars are the main source of s process nucleosynthesis and have atmospheres observed by astronomers to be highly enriched in dredged-up s process elements. The S-process or slow-neutron -capture-process is a Nucleosynthesis process that occurs at relatively low neutron density and intermediate temperature conditions in The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass Stars This is a period of Stellar evolution Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons Another dramatic example comes from the supernova condensates, usually shortened by acronym to SUNOCON to distinguish them from other stardust condensed within stellar atmospheres. SUNOCONs show evidence that they condensed containing abundant radioactive 44Ti, which has a 65 yr halflife. It was thus still alive when the SUNOCON condensed within the expanding supernova interior but would have been extinct after mixing with the interstellar gas. Its discovery proved the prediction from 1975 to identify SUNOCONs in this way. But SiC SUNOCONs are only about 1% as numerous as are SiC stardust.

Exciting as stardust is, it is but a modest fraction of the condensed cosmic dust. It seems that stardust is less than 0. 1% of the mass of total interstellar solids. Its interest lies in the new information that it has brought to the sciences of stellar evolution and nucleosynthesis. Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons

A fascinating aspect to human culture is the study within terrestrial laboratories of solids that existed before the earth existed. This was once thought impossible, especially in the decades when cosmochemists were confident that the solar system began as a hot gas virtually devoid of any remaining solids, which would have been vaporized by high temperature. The very existence of stardust shows that that historic picture was incorrect.

Some bulk properties of cosmic dust

Smooth chondrite interplanetary dust particle. Courtesy of E. K. Jessberger, Institut für Planetologie, Münster, Germany, and on Brownlee, University of Washington, Seattle, under a cc-a-2. 5 license.

Cosmic dust is made of dust grains and aggregates of dust grains. These particles are irregularly-shaped with porosity ranging from fluffy to compact. Porosity is a measure of the void spaces in a material and is measured as a fraction between 0–1 or as a Percentage between 0–100% The composition, size, and other properties depends on where the dust is found, and conversely, a compositional analysis of a dust particle can reveal the much about the dust particle's origin. General diffuse interstellar medium dust, dust grains in dense clouds, planetary rings dust, and circumstellar dust, are each different in their characteristics. Interstellar cloud is the generic name given to an accumulation of gas plasma and dust in our and other galaxies. A planetary ring is a ring of Cosmic dust and other small particles Orbiting around a Planet in a flat disc-shaped region For example, grains in dense clouds have acquired a mantle of ice and on average are larger than dust particles in the diffuse interstellar medium. Interplanetary dust particles (IDPs) are generally larger still.

Major elements of 200 stratospheric interplanetary dust particles. Courtesy of Thomas Stephan, Institut für Planetologie, Münster, Germany, under a cc-a-2. 5 license.

Most of the influx of extraterrestrial matter that falls onto the Earth is dominated by meteoroids with diameters in the range 50 to 500 micrometers, of average density 2. 0 g/cm³ (with porosity about 40%). The densities of most IDPs captured in the earth's stratosphere range between 1 and 3 g/cm³, with an average density at about 2. The interplanetary dust cloud is Cosmic dust (small particles floating in space which pervade the space between Planets in the Solar System and in The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 0 g/cm³. ^[4]

Other specific dust properties:

• In circumstellar dust, astronomers have found molecular signatures of CO, silicon carbide, amorphous silicate, polycyclic aromatic hydrocarbons, water ice, and polyformaldehyde, among others. (In the diffuse interstellar medium, there is evidence for silicate and carbon grains. )
• Cometary dust is generally different (with overlap) from asteroidal dust. Comet dust refers to Cosmic dust that originates from a Comet. Asteroidal dust resembles carbonaceous chondritic meteorites, and cometary dust resembles interstellar grains, which can include the elements: silicates, polycyclic aromatic hydrocarbons, and water ice. A carbonaceous chondrite or a C-type chondrite is a type of chondritic Meteorite which contains high levels of Water and Organic compounds Polycyclic aromatic hydrocarbons ( PAH s are Chemical compounds that consist of fused Aromatic rings and do not contain Heteroatoms or

Dust grain formation

The large grains start with the silicate particles forming in the atmospheres of cool stars, and carbon grains in the atmospheres of cool carbon stars. A carbon star is a late type giant star similar to the Red giants (or occasionally Red dwarf) Star whose atmosphere contains more Carbon than Stars, which have evolved off the main sequence, and which have entered the giant phase of their evolution, are a major source of dust grains in galaxies. The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness A giant star is a Star with substantially larger Radius and Luminosity than a Main sequence star of the same surface temperature. Star dust, sung and written in the popular media, is a colloquial term referring to the birthplace of most dust grains in the Universe. If one indeed traces the origin of the elements out of which our bodies are made, we are star dust.

Astronomers know that the dust is formed in the envelopes of late-evolved stars from specific observational signatures. An (infrared) 9. 7 micrometre emission silicate signature is observed for cool evolved (oxygen-rich giant) stars. And an (infrared) 11. 5 micrometre emission silicon carbide signature is observed for cool evolved (carbon-rich giant) stars. These help provide evidence that the small silicate particles in space came from the outer envelopes (ejecta) of these stars. ^[5]label

It is believed that conditions in interstellar space are generally not suitable for the formation of silicate cores. The arguments are that: given an observed typical grain diameter a, the time for a grain to attain a, and given the temperature of interstellar gas, it would take considerably longer than the age of the universe for interstellar grains to form ^label. Furthermore, grains are seen to form in the vicinity of nearby stars in real-time, meaning in a) nova and supernova ejecta, and b) R Coronae Borealis, which seem to eject discrete clouds containing both gas and dust. A nova (pl novae or novas) is a Cataclysmic nuclear explosion caused by the accretion of hydrogen onto the surface of a White A supernova (plural supernovae or supernovas) is a stellar Explosion.

Most dust in our solar system is highly processed dust, recycled from the material out of which our solar system formed and subsequently collected in the planetesimals, and leftover solid material (for example: comets and asteroids), and reformed in each of those bodies' collisional lifetimes. A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — Asteroids, sometimes called Minor planets or planetoids', are bodies—primarily of the inner Solar System —that are smaller than planets but During our solar system's formation history, the most abundant element was (and still is) H₂. The metallic elements: magnesium, silicon, and iron, which are the principal ingredients of rocky planets, condensed into solids at the highest temperatures. The range of elements of the solar nebula between H₂ and (Mg, Si, Fe) is not known well (Wood, J. , 1999). Some molecules such as CO, N₂, NH₃, and free oxygen, existed in a gas phase. Some molecules, for example, graphite (C) and SiC condensed into solid grains. Some molecules also formed complex organic compounds and some molecules formed frozen ice mantles, of which either could coat the "refractory" (Mg, Si, Fe) grain cores.

The formation of these molecules was determined, in large part, by the temperature of the solar nebula. Since the temperature of the solar nebula decreased with heliocentric distance, scientists can infer a dust grain's origin(s) with knowledge of the grain's materials. Some materials could only have been formed at high temperatures, while other grain materials could only have been formed at much lower temperatures. The materials in a single interplanetary dust particle often show that the grain elements formed in different locations and at different times in the solar nebula. Most of the matter present in the original solar nebula has since disappeared; drawn into the Sun, expelled into interstellar space, or reprocessed, for example, as part of the planets, asteroids or comets.

Due to their highly-processed nature, IDPs are fine-grained mixtures of thousands to millions of mineral grains and amorphous components. An amorphous solid is a Solid in which there is no Long-range order of the positions of the Atoms (Solids in which there is long-range atomic order are We can picture an IDP as a "matrix" of material with embedded elements which were formed at different times and places in the solar nebula and before our solar nebula's formation. The formation and evolution of the Solar System is estimated to have begun Examples of embedded elements in cosmic dust are GEMS, chondrules, and CAIs. Glass with Embedded Metal and Sulfides (GEMS are tiny spheroids in Cosmic dust particles with bulk compositions that are approximately chondritic Most Meteorites that fall on Earth are Chondrites which are characterized by the presence of round grains called chondrules (from Ancient Greek A calcium-aluminium-rich inclusion or Ca-Al-rich inclusion (CAI is a Centimeter -sized light-colored Calcium - and Aluminium -rich inclusion

A Dusty Trail from the Solar Nebula to Earth

A dusty trail from the early solar system to carbonaceous dust today. Courtesy of Amara Graps, Planetary Science Institute, Tucson, Arizona, released to the public domain.

The arrows in the adjacent diagram show one possible path from a collected interplanetary dust particle back to the early stages of the solar nebula.

We can follow the trail to the right in the diagram to the IDPs that contain the most volatile and primitive elements. The trail takes us first from interplanetary dust particles to chondritic interplanetary dust particles. Planetary scientists classify chondritic IDPs in terms of their diminishing degree of oxidation so that they fall into three major groups: the carbonaneous, the ordinary, and the enstatite chondrites. As the name implies, the carbonaceous chondrites are rich in carbon, and many have anomalies in the isotopic abundances of H, C, N, and O (Jessberger, 2000). From the carbonaceous chondrites, we follow the trail to the most primitive materials. They are almost completely oxidized and contain the most low condensation temperature elements ("volatile" elements) and the largest amount of organic compounds. Therefore, dust particles with these elements are thought to be formed in the early life of our solar system. Why? The volatile elements have never seen temperatures above about 500 K, therefore, one can conclude that the IDP grain "matrix" consists of some very primitive solar system material. Such a scenario is true in the case of comet dust^[6].

We can learn more about these particles' origin, by examining their surfaces. If we examine, in the laboratory, dust particles' density of solar flare tracks, their amorphous rims, and the spallogenic isotopes from cosmic rays (Flynn, 1996), then we have good clues for how long a particle has been travelling in space. Nuclear damage tracks are caused by the ion flux from solar flares. Solar wind ions impacting on the particle's surface produce amorphous radiation damaged rims on the particle's surface. And spallogenic nuclei are produced by galactic and solar cosmic rays. A dust particle that originates in the Kuiper Belt at 40AU would have many more times the density of tracks, thicker amorphous rims and higher integrated doses than a dust particle originating in the main-asteroid belt.

Dust grain destruction

How are the interstellar grains destroyed? There are several ultraviolet processes which lead to grain "explosions"^[7][8]. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays In addition, evaporation, sputtering (when an atom or ion strikes the surface of a solid with enough momentum to eject atoms from it), and grain-grain collisions have a major influence on the grain size distribution. Sputtering is a process whereby Atoms are Ejected from a solid target material due to bombardment of the target by energetic Ions It is commonly used for ^label

These destructive processes happen in a variety of places. Some grains are destroyed in the supernovae/novae explosion (and others are formed afterwards). Some of the dust is ejected out of the protostellar disk in the strong stellar winds that occur during a protostar's active T Tauri phase and may be destroyed when passing through shocks, e. A protostar is a large object that forms by contraction out of the gas of a Giant molecular cloud in the Interstellar medium. T Tauri stars ( TTS) are a class of variable Stars named after their prototype – T Tauri. g. in Herbig-Haro objects. Herbig-Haro objects are small patches of nebulosity associated with newly-born Stars and are formed when Gas ejected by young Stars collides Plus there are some gas-phase processes in a dense cloud where ultraviolet photons eject energetic electrons from the grains into the gas.

Dust grains incorporated into stars are also destroyed, but only a relatively small fraction of the mass of a star-forming cloud actually ends up in stars. This means a typical grain goes through many molecular clouds and has mantles added and removed many times before the grain core is destroyed. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar

Some "dusty" clouds in the universe

Our solar system has its own interplanetary dust cloud; extrasolar systems too. The interplanetary dust cloud is Cosmic dust (small particles floating in space which pervade the space between Planets in the Solar System and in

There are different types of nebulae with different physical causes and processes. One might see these classifications:

• diffuse nebula
• infrared (IR) reflection nebula
• supernova remnant
• molecular cloud
• HII regions
• photodissociation regions

Distinctions between those types of nebula are that different radiation processes are at work. In Astronomy, diffuse nebulae is the general term for illuminated Nebulae The three types of diffuse nebulae are Reflection nebulae Emission In Astronomy, reflection nebulae are clouds of dust which are simply reflecting the light of a nearby Star or stars A supernova remnant ( SNR) is the structure resulting from the gigantic explosion of a Star in a Supernova. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar An H II region (also known as Emission nebula) is a cloud of glowing Gas and plasma, sometimes several hundred Light-years across For example, H II regions, like the Orion Nebula, where a lot of star-formation is taking place, are characterized as thermal emission nebulae. The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a Diffuse nebula situated south of Orion 's Belt Supernova remnants, on the other hand, like the Crab Nebula, are characterized as nonthermal emission (synchrotron radiation). The Crab Nebula  (catalogue designations M 1 NGC 1952 Taurus A is a Supernova remnant and Pulsar wind nebula in the Constellation This article concerns the physical phenomenon of synchrotron radiation

Some of the better known dusty regions in the universe are the diffuse nebula in the Messier catalog, for example: M1, M8, M16, M17, M20, M42, M43 Messier Catalog

Some larger 'dusty' catalogs that you can access from the NSSDC, CDS, and perhaps other places are:

• Sharpless (1959) A Catalogue of HII Regions
• Lynds (1965) Catalogue of Bright Nebulae
• Lunds (1962) Catalogue of Dark Nebulae
• van den Bergh (1966) Catalogue of Reflection Nebulae
• Green (1988) Rev. The Crab Nebula  (catalogue designations M 1 NGC 1952 Taurus A is a Supernova remnant and Pulsar wind nebula in the Constellation The Lagoon Nebula (also known as Messier Object 8 ( M8) and NGC 6523) is a giant interstellar cloud classified as an Emission nebula For an object in the constellation of Canis Major also called Eagle nebula see Seagull Nebula. The Omega Nebula (also known as the Swan Nebula, Messier 17 or NGC 6618) is an H II region in the Constellation Sagittarius The Trifid Nebula (also known as Messier 20 and NGC 6514) is an H II region located in Sagittarius. The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a Diffuse nebula situated south of Orion 's Belt Messier 43 (also known as M43, De Mairan's Nebula, and NGC 1982) is an H II region in the Orion constellation. Reference Cat. of Galactic SNRs

at

• The National Space Sciences Data Center (NSSDC)
• CDS Online Catalogs

Images

Comet dust

Asteroidal dust

NASA airplane collector plate

Collecting pool

References

^backEvans94  Evans, Aneurin (1994). The Dusty Universe. Ellis Horwood.  

^backJess92  Jessberger, Elmar K. ; Bohsung, Joerg; Chakaveh, Sepideh; Traxel, Kurt (August 1992). "The volatile element enrichment of chondritic interplanetary dust particles". Earth and Planetary Science Letters 112, No. 1-4: 91–99.  

External links

• Cosmic Dust Glossary