21. UCL Centre For Cosmic Chemistry And Physics University College London. Research into the chemistry which occurs throughout the universe in interstellar space. http://www.chem.ucl.ac.uk/cosmicdust/

@import url(/css/fonts.css); @import url(/css/extras.css); UCL Centre for Cosmic Chemistry and Physics CCCP About the Centre The People Contact Us Our Publications ... Stars 'R' Us About the Centre for Cosmic Chemistry and Physics The purpose of the Centre is to apply research to fundamental chemical processes which are believed to occur throughout the universe. A recent review of the activities of the Centre can be found here Using a unique combination of theoretical and experimental techniques , such processes are investigated in the laboratory. Comparison of these results with astronomical models and observations serves to increase our knowledge and understanding of the cosmos. Our first major project concerns the formation of hydrogen molecules on surfaces of interstellar dust grains and the second expands upon this to study the formation of more complex molecules such as methanol. You can view a pdf document explaining the motivations and experimental activities of the centre here and we now have a resource available following our successful Stars 'R' Us display at the recent Royal Society Summer Exhibition.

22. Interstellar Molecules-Evolutionary Cycle Evolutionary cycle of Interstellar Organic Molecules - Fullerenes, PAHs, Polyyenes, and biomolecules. http://www.shantanurastogi.homestead.com/files/ismol.html

Welcome to the Universe of Astrophysical Molecules Molecules have been observed in astronomical environments as diverse as comets in the solar system and galaxies at the highest redshifts. They act as excellent probes of the physical structure and dynamics of such regions, owing to the complexity of their energy level structure and the resulting emission and absorption spectra. In addition, molecules also play an active role in the energy balance of clouds. Interstellar space is a unique laboratory in which chemical processes can occur that are not normally found on Earth. Astrochemistry, a highly interdisciplinary subject, links the macrocosm (galaxies, stars, planets) with the microcosm (basic chemical processes and spectroscopy). The ground-and space-based observational facilities over complete wavelength range makes it possible to study the development of molecular complexity throughout the universe. The illustration, taken from Carbon plays a very important role also in Space Astrochemistry . The interstellar clouds contain simple Carbonaceous molecules such as CO, formaldehyde, ether etc. but also more complex species like polyynes Polycyclic aromatic hydrocarbons Fullerenes etc., which along with graphite and chains makeup for a large fraction of Interstellar Carbon. CO and Cyanide can be detected in young stellar objects. Amino acids and formic acid are detected in meteorites and comets.

23. Interstellar Medium - Article And Reference From OnPedia.com The interstellar medium (or ISM) is a term used in astronomy to describe the rarefied gas and dust th http://www.onpedia.com/encyclopedia/interstellar-medium

Other Definitions interstellar medium (dict) Interstellar Medium The interstellar medium (or ISM ) is a term used in astronomy to describe the rarefied gas and dust that exists between the stars (or their immediate "circumstellar" environment) within a galaxy . The matter normally consists of about 99% gas particles and usually 1% of dust. It fills interstellar space . This compound is usually extremely tenuous, with typical densities ranging from a few single to a few hundreds of a particles per cubic centimeter. Generally the gas is roughly 90% hydrogen and 10% helium, with additional elements (" metals " in astronomical parlance) present in trace amounts. The medium is also responsible for cosmic extinction , namely the decreasing light intensity of a star as the light travels through the medium. This extinction is caused by refraction and absorption of photons in certain wavelengths. For example, a typical absorption wavelength of atomic hydrogen lies at ca. 121.5 nm, the Lyman-alpha transition. Therefore, it is nearly impossible to see light emitted at that wavelength from a star, because most of it is absorbed during the trip to Earth by Lyman-alpha absorption. The interstellar medium is usually divided into three phases , depending on the temperature of the gas: hot (millions of kelvins ), warm (thousands of kelvins), and cold (tens of kelvins). This "three-phase" model of the ISM was initially developed by

24. Seth Redfield Has A New URL and visualizations of the Local Interstellar Cloud, a column density calculator for it, and links to popular articles and research papers....... http://cobalt.as.utexas.edu/~sredfield/

Seth Redfield's web site has moved to: https://wesfiles.wesleyan.edu/home/sredfield/web/ Please bookmark this new URL. You will automatically be redirected in 20 seconds.

25. The Interstellar Medium Although space is very empty and the stars in the Milky Way are very far apart, the space between the stars contains a very diffuse medium of gas and dust astronomers call the http://cass.ucsd.edu/public/tutorial/ISM.html

University of California, San Diego Gene Smith's Astronomy Tutorial The Interstellar Medium Although space is very empty and the stars in the Milky Way are very far apart, the space between the stars contains a very diffuse medium of gas and dust astronomers call the interstellar medium (ISM) . This medium consists of neutral hydrogen gas (HI), molecular gas (mostly H ), ionized gas (HII), and dust grains. Although the interstellar medium is, by several orders of magnitude, a better vacuum than any physicists can create in the laboratory there is still about of 5-10 billion M of gas and dust out there, comprising approximately 5% of the mass of visible stars in the Galaxy. Neutral Hydrogen Gas The Milky Way Galaxy is filled with a very diffuse distribution of neutral hydrogen gas which has a typical density of about 1 atom/cm g/cm ). The interstellar medium is far too cool to excite the UV or optical transitions of hydrogen, but there is a feature at 21 cm wavelength in the radio produced by the spins (magnetic fields) of the hydrogen atom's nuclear proton and orbiting electron. Because the proton and electron are spinning distributions of electric charge they create minute magnetic fields which interact, creating a small energy difference between the state in which the poles are aligned versus counter-aligned. This energy difference corresponds to the energy of radio waves at 21-centimeters. Every once in a while (about once per 500 years) hydrogen atoms will collide, exciting an atom into the higher energy spin-aligned configuration. It will take as long as 30 million years for the atom to jump back to the lower energy state via a

26. FusEdWeb | Fusion Education Part of a site on plasma physics. http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula/Reflection.html

skip to: page content links on this page site navigation footer (site information) Bringing The Power Source of the Stars Down to Earth Home CPEP: Online Fusion Course Plasmas - the 4 th ... Nebulae CPEP: Online Fusion Course Main Topics Energy Sources and Conversions Two Key Fusion Reactions How Fusion Reactions Work Creating the Conditions for Fusion ... Achieving Fusion Conditions More Info About CPEP Fusion Chart Images: English + 6 More Languages Main CPEP Web Site Printed Charts in 3 Sizes Webby Awards Honoree April 10, 2007 Links Go - Fusion November 9, 1998 Overview The Guided Tour Reflection Nebulae The Pleiades (Click for a larger image) Photo Credit: David Malin at the Anglo-Australian Observatory ; used with permission - please do not redistribute without permission! Reflection nebulae are not glowing plasmas but are visible because of light from nearby bright stars scattering off of dust particles. The nearby star or stars are not hot enough to cause ionization in the gas of the nebula but are bright enough to give sufficient scattering to make the dust visible. Since wavelengths in the blue are scattered more readily than red, reflection nebula tend to have a blue shading. (This is the same scattering process that gives us blue skies and red sunsets.) Among the nicest of the reflection nebulae are those surrounding the stars of the Pleiades. A blue reflection nebula can also be seen in the same area of the sky as the

27. Interstellar Medium And The Milky Way Gas Chapter index in this window — — Chapter index in separate window This material (including images) is copyrighted!. See my copyright notice for fair use practices. http://www.astronomynotes.com/ismnotes/s3.htm

Gas Chapter index in this window Chapter index in separate window This material (including images) is . See my for fair use practices. Select the photographs to display the original source in another window. Most of the ground-based telescope pictures here are from the Anglo-Australian Observatory (AAO-used by permission). Links to external sites will be displayed in another window. About 99% of the interstellar medium is gas with about 90% of it in the form of hydrogen (atomic or molecular form), 10% helium, and traces of other elements. At visible wavelengths, however, dust has a greater effect on the light than the gas. The presence of interstellar gas can be seen when you look at the spectral lines of a binary star system. Among the broad lines that shift as the two stars orbit each other, you see narrow lines that do not move. The narrow lines are from much colder gas in the interstellar medium between us and the binary system. The hydrogen gas is observed in a variety of states: in ionized, neutral atomic, and molecular forms. The ionized hydrogen emits light in the visible band as the electrons recombine with the protons and the neutral atomic and molecular hydrogen emits light in the radio band of the electromagnetic spectrum. H II Regions H II regions Below is a famous H II region called the Orion Nebula . It is the fuzzy patch you can see in the sword part of the Orion constellation. It is the closest large star formation factory to us and is explored in more detail in the

28. Interstellar Medium | Universe Today List of Constellations; List of Messier Objects; OneWay, One-Person Trip to Mars; Maximizing Survival Time Inside the Event Horizon of a Black Hole http://www.universetoday.com/tag/interstellar-medium/

29. Planetary Nebula Sampler General information and photos. http://www.noao.edu/jacoby/pn_gallery.html

NOAO Outreach A Planetary Nebula Sampler Other NOAO Image pages Image Gallery Planetary Nebula Advanced Observing Program AOP Planetary Nebula Index of Nebula Abell 35 Abell 39 Abell 78 M 22 ... Saturn Nebula A planetary nebula forms when a star can no longer support itself by fusion reactions in its center. The gravity from the material in the outer part of the star takes its inevitable toll on the structure of the star, and forces the inner parts to condense and heat up. The high temperature central regions drive the outer half of the star away in a brisk stellar wind, lasting a few thousand years. When the process is complete, the remaining core remnant is uncovered and heats the now distant gases and causes them to glow. Why "Planetary" Nebula? Despite the name, these objects are totally unrelated to "planets". It is commonly thought that they may represent the final episode of the Sun's existence as a star. This concept has been questioned recently by Jacoby, Fullton, Morse, Kwitter and Henry ( 1997) and Bond (2001) - wherein evidence from globular cluster stars indicates that stars must be about 20% heavier than the Sun to form a PN. It is estimated that there are about 10,000 planetary nebulae in our galaxy, so they are a relatively common, although short-lived phase (about 25,000 years) of the stellar life cycle.

30. Interstellar Medium Interstellar Medium This set of notes by Nick Strobel covers the interstellar mediumthe effect of dust, emission nebulae, 21 cm radiation, mapping galactic structure, and http://www.maa.mhn.de/Scholar/interstmat.html

Interstellar Medium This set of notes by Nick Strobel covers: the interstellar mediumthe effect of dust, emission nebulae, 21 cm radiation, mapping galactic structure, and molecules.These notes will be in outline form to aid in distinguishing various concepts. As a way to condense the text down I'll often use phrases instead of complete sentences. The vocabulary terms are italicized. Contents Interstellar Medium (ISM) Dust Extinction Reddening ... Molecules Molecular clouds Photo Gallery of Nebulae (Under construction) Interstellar Medium (ISM) Index Stuff between the stars. 10-15% of the visible mass of the Galaxy. 99% of the ISM mass is gas; 1% dust. ``So what?'' Why do we worry about the interstellar medium? The interstellar medium affects starlight and stars are formed from ISM! A. Dust Dust -about the size of the wavelength blue light or smaller. Water ice, graphite (Carbon), Silicon in highly flattened flakes or needles. Effects of dust on light: Extinction Extinction dimming of starlight at all wavelengths. In 1930 R.J. Trumpler plots angular diameter of clusters vs. distance to cluster. Distance found from inverse square law of brightness. IF clusters all have nearly same linear diameter s , then the angular diameter should equal a constant size / distance ( theta = s/D ). But he found a

31. FusEdWeb | Fusion Education A short discussion, part of a web page on plasmas. http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula/Planetary.html

skip to: page content links on this page site navigation footer (site information) Bringing The Power Source of the Stars Down to Earth Home CPEP: Online Fusion Course Plasmas - the 4 th ... State of Matter CPEP: Online Fusion Course Main Topics Energy Sources and Conversions Two Key Fusion Reactions How Fusion Reactions Work Creating the Conditions for Fusion ... Achieving Fusion Conditions More Info About CPEP Fusion Chart Images: English + 6 More Languages Main CPEP Web Site Printed Charts in 3 Sizes Webby Awards Honoree April 10, 2007 Links Go - Fusion November 9, 1998 Overview The Guided Tour Planetary Nebulae A planetary nebula can result as a star with mass of less than several times the solar mass ("low mass" star) ejects mass in the red giant stage, near the end of the star's life. In this stage, the central part of the star, which is about the size of the earth, consists of a carbon ash core, a shell in which helium is fusing to carbon, and a shell where fusion of hydrogen to helium has temporarily ceased. The rest of the star's envelope has expanded to about 70 times larger than it had during most of its lifetime (almost the size of the orbit of Mars). The star at the center of the nebula is extremely hot, reaching temperatures of 200,000 K, emitting a large amount of the ultraviolet radiation which is necessary for ionization of hydrogen in the expanding gas. The resulting plasma is similar to that in the

32. Interstellar Matter: Information From Answers.com Content of the region between the stars, including vast, diffuse clouds of gases and minute solid particles. Such tenuous matter in the Milky Way Galaxy accounts for about 5% http://www.answers.com/topic/interstellar-medium-2

var isReferenceAnswers = true; BodyLoad('s'); On this page Library Animal Life Health History, Politics, Society ... Technology interstellar matter Britannica Concise Encyclopedia: interstellar medium Home Library Miscellaneous Britannica Concise Encyclopedia Content of the region between the stars, including vast, diffuse clouds of gases and minute solid particles. Such tenuous matter in the Milky Way Galaxy accounts for about 5% of its total mass. By no means a complete vacuum, the interstellar medium contains mainly hydrogen gas, with a smaller amount of helium and sizable quantities of dust particles of uncertain composition. Primary cosmic ray s also travel through interstellar space, and magnetic fields extend across much of it. Most interstellar matter occurs in cloudlike concentrations, which can condense to form star s. Stars, in turn, continually lose mass through stellar winds ( see solar wind Supernova s and planetary nebula e also feed mass back to the interstellar medium, where it mixes with matter that has not yet formed stars ( see Populations I and II For more information on interstellar medium , visit Britannica.com

33. Variability Of Planetary Nebula Central Stars General information and links. http://www.astro.psu.edu/users/rbc/res_puls.html

34. Interstellar Medium Definition Of Interstellar Medium In The Free Online Encyclo interstellar medium. Content of the region between the stars, including vast, diffuse clouds of gases and minute solid particles. Such tenuous matter in the Milky Way Galaxy accounts http://encyclopedia2.thefreedictionary.com/interstellar medium

35. Planetary Nebulae Gallery A data table with links to images. http://home.austarnet.com.au/mhorn/pneb.html

Planetary Nebulae Gallery Object Const Mag Size R.A. Dec. Type Cent.Star Abell 1 CEP 18.3 47" 00 12.6 +69 11 2b 19.9 Abell 2 CAS 14.4 33"x29" 00 45.6 +57 57 2c 19.8 Abell 3 CAS 18.2 60" 02 12.2 +64 09 3b 18.1 Abell 35 Text HYA 12.0 709" 12 53.6 -22 52 3a 9.6 Abell 39 Text HER 12.9 174" 16 27.5 +27 54 2c 15.8 Abell 78 Text CYG 14.3 101" 21 35.5 +31 42 4 13.3 Abell 79 LAC 15.8 59"x49" 22 26.6 +54 49 4(3) 18.4 Ack 277-03.1 CRL 2688 Text CYG 13.5 27" 21 02.3 +36 42 Note Egg Nebula CRL 2688 Text IC 418 Text LEP 10.7 14"x11" 05 27.5 -12 42 4 11.0 IC 2149 Text AUR 10.0 12"x6" 05 56.3 +46 07 3b(2) 10.5 IC 4406 LUP 11.0 28" 14 22.4 -44 09 4(3) 14.7 IC 4593 Text HER 11.0 12" 16 12.2 -12 04 2(2) 11.2 J 320 Text ORI 12.9 11"x8" 05 05.6 +10 42 2(4) 13.5 Text MON 13.9 3" 07 37.3 -09 39 ?(4) 16.9 Text OPH 14.6 39"x15" 17 05.7 -10 09 ?(6) Menzel 1 NOR 12.5 26" 15 34.2 -59 09 4(6) Text Hourglass Nebula NGC 650-1 Text PER 11.0 65" 01 42.4 +51 34 3(6) 17.0 NGC 650-1 Text NGC 1360 FOR 7.0 360" 03 33.3 -25 51 3 11.4

36. Interstellar Medium Interstellar medium . in order for an interstellar cloud to collapse gravitationally, it must A not have any spin. B have a very large mass. http://webs.wichita.edu/astronomy/Testbank/ism.htm

Interstellar medium in order for an interstellar cloud to collapse gravitationally, it must A not have any spin. B have a very large mass. C be made mostly of hydrogen. D have a low internal pressure compared to its gravity. E have a high internal pressure compared to its gravity. 21-cm radiation has yielded important information about A the density of helium in the universe B the physical structure of our galaxy C the prevalence of water in the universe D the spin-flip propensities of methyl alcohol (ch2oh) dark clouds are best studied through examination of A interstellar absorption lines in the spectra of distant stars B Balmer emission lines C radio waves emitted by molecules D ultraviolet radiation emitted by the gas interstellar molecules are most abundant in A dark clouds B emission nebulae C reflection nebulae D between spiral arms interstellar 21-cm radiation is emitted by A water B methyl alcohol C helium D hydrogen most interstellar molecules reveal their presence by radiating A infrared wavelengths B ultraviolet wavelengths C x-rays D radio wavelengths the 21-centimeter line arises from which of the following?

37. FusEdWeb | Fusion Education Part of a site on plasma physics. http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula/Emission.html

skip to: page content links on this page site navigation footer (site information) Bringing The Power Source of the Stars Down to Earth Home CPEP: Online Fusion Course Plasmas - the 4 th ... Nebulae CPEP: Online Fusion Course Main Topics Energy Sources and Conversions Two Key Fusion Reactions How Fusion Reactions Work Creating the Conditions for Fusion ... Achieving Fusion Conditions More Info About CPEP Fusion Chart Images: English + 6 More Languages Main CPEP Web Site Printed Charts in 3 Sizes Webby Awards Honoree April 10, 2007 Links Go - Fusion November 9, 1998 Overview The Guided Tour Emission Nebulae The Trifid Nebula (Click for larger rendering) Photo Credit: David Malin at the Anglo-Australian Observatory ; used with permission - please do not redistribute without permission! (See also the false-color Hubble Telescope image of the Orion Nebula ; this has buttons for text and for either jpeg or gif images. The HII regions (emission nebulae) are so named because they are composed mostly of a plasma of ionized hydrogen (HII) and free electrons. The hydrogen atoms of the interstellar medium are ionized by the ultraviolet radiation from a nearby star or stars. Only very hot stars, typically young stars, have enough radiation in the ultraviolet region at wavelengths necessary to ionize the hydrogen. The excess energy beyond that needed to ionize the hydrogen goes to kinetic energy of the ejected electrons. Eventually, by collision, this energy is shared by other particles in the gas. An equilibrium is established in a typical emission nebula when the temperature equivalent of this kinetic motion is between 7000 K and 20,000 K. For a typical emission nebulae, the density of ions (and electrons) is 1.0E8 to 1.0E10 particles per m^3.

38. Interstellar Medium: Cold When one looks up into the night sky we only see stars and the occasional planet. Most of outer space is empty, meaning that the density of atoms is much lower than even the best http://abyss.uoregon.edu/~js/ast122/lectures/lec22.html

Interstellar Medium When one looks up into the night sky we only see stars and the occasional planet. Most of outer space is empty, meaning that the density of atoms is much lower than even the best vacuums in our labs. Deep imaging of the skies showed that there are numerous regions where interstellar matter, in the form of gas and dust, collects to form clouds and nebula. Since these clouds are diffuse, they are difficult to see with the naked eye. The first indication that there was interstellar gas and dust was dark lanes in the Milky Way. Since we live in a disk galaxy, then looking outward we see a band of light in the sky which, if magnified, breaks down into the many stars in our Galaxy. A deep photo of the Milky Way shows that there are dark regions or lanes. We understand now that there is gas and dust blocking the starlight which produces these dark lanes, such as the CoalSack Nebula . In fact, most of our Galaxy is blocked from our view by patches of gas and dust Interstellar Extinction Astrophotograph in the 19th century showed that the dark lanes or holes in the Milky Way did not have sharp edges. That, in fact, detail studies of star clusters at various distances from us showed that the intensity of light from remote stars is reduced as it passes through the sparse material of the interstellar medium. Herschel tried to use star counts to measure the size of the Galaxy and where our position is within it. His result was the diagram below, but what he really discovered was that interstellar extinction limits our line of sight.

39. Cyanodiacetylene Spectroscopy And Photochemistry Paper by Marcin Gronowski, Institute of Physical Chemistry, Polish Academy of Sciences. Results of spectroscopy, photochemistry and theoretical study on the cyanodiacetylene and related isomers in the interstellar medium. http://marcingronowski.googlepages.com/2008_03_20_CDA_Marcin_Gronowski.pdf

40. Lecture 11: Interstellar Medium ``They cannot scare me with their empty spaces Between stars on stars where no human race is. I have it in me so much nearer home To scare myself with my own desert places.'' http://www.astronomy.ohio-state.edu/~ryden/ast162_3/notes11.html

Astronomy 162: Professor Barbara Ryden Tuesday, January 21 INTERSTELLAR MEDIUM ``They cannot scare me with their empty spaces Between stars - on stars where no human race is. I have it in me so much nearer home To scare myself with my own desert places.'' - Robert Frost Key Concepts The interstellar medium consists of low-density gas and dust. Interstellar gas consists of cool clouds embedded in hot intercloud gas. The interstellar medium emits, absorbs, and reflects radiation. (1) The interstellar medium (that's just a fancy name for the matter between stars) consists of low-density gas and dust. The fact that we can look out far into the galaxy means that there must be very little matter between stars otherwise it would absorb all the starlight. Nevertheless, interstellar space is not entirely empty. 99% of the interstellar medium consists of very low density gas. How low in density is it? Let me tell you. The air we breathe has a density of approximately 10 molecules per cubic centimeter. (One cubic centimeter = 1 milliliter = 1/1000 liter). By contrast, the lowest density regions of interstellar space contains approximately 0.1 atoms per cubic centimeter.

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