21. The Astrophysics Spectator: An Introduction To The Interstellar Medium Gas, dust, magnetic field, and cosmic rays fill the space between the stars. http://www.astrophysicsspectator.com/topics/milkyway/InterstellarMedium.html

The Astrophysics Spectator Home Topics Interactive Pages Commentary ... Information Search Site Milky Way Galaxy Structure of the Milky Way The Galactic Center The Sagittarius A Complex Massive Stars of Sgr A* ... Cold Clouds, Warm Gas Tables Properties of the Galaxy Orbital Parameters of Stars Orbiting Sgr A* Milky Way Galaxy The Interstellar Medium The space between the stars is not a pure vacuum, as is attested by the gaps in the Milky Way; cool clouds of gas and dust within the Galactic plane block out the light of the more distant stars. Less apparent is the tenuous, warm gas that pervades the Galactic disk. Together these two components of the interstellar medium (ISM in the astronomical jargon) fill about half of the space of the Galactic disk. The remainder is fill with extremely low-density gas, much of which is extremely hot. Even the most dense regions of the Galaxy are hard vacuums, with the number of molecules reaching only 10 per cubic centimeter. These regions are the cores of molecular clouds, and they are very cold, with a temperature of around 10° Kelvin. The more common cool regions have a density of several 10s of atoms per cubic centimeter and a temperature below 100° K. In the warm-gas regions of the Galaxy, the density is only about 1 atom per cubic centimeter, but the temperature is several thousand degrees K. The region within 50 parsecs of the Sun is an example of the lowest-density regions of the Galaxy; the hot bubble we sit in has a density of only 0.1 atoms per cubic centimeter and a temperature of about 1 million degrees K. Besides these hot low-density regions, there are cool low-density regions. All total, the average density at the Galactic plane is a little over 1 atom per cubic centimeter. But because of the great distances between the stars, the amount of mass in the interstellar medium rivals the amount of mass in stars. Recent research places the mass density at the galactic plane at 0.076 solar masses per cubic parsec, which means the fraction of mass in gas and dust is about 30% of the total mass.

22. According To An Interstellar Medium... Within about 50000 years, the solar system could enter a much denser portion of the interstellar medium. How would that affect our atmosphere? http://whyfiles.org/017planet/gas_cloud2.html

It looks as if our trusty ol' solar system is poised to enter a "dense" cloud of interstellar gas, an event that would change our atmosphere in unpredictable ways. But not to worry it's not going to happen for several tens of thousands of years. Within about 50,000 years, the solar system could enter a much denser portion of the interstellar medium. How would that affect our atmosphere? Yellow arrow: sun's movement through space. White arrows: movement of gas cloud. Courtesy of Priscilla Frisch, the University of Chicago. Could the denser gas in "outer space" affect the atmosphere, and conditions on our planet? That's something that Priscilla Frisch, an astronomer at University of Chicago, wonders about. She notes that for the past 5 to 10 million years, Earth has occupied a region that's "virtually empty." When she says "virtually," she's serious : The interstellar medium now has about 0.1 hydrogen atom per cubic centimeter (and that's 1,000 times as dense as the last cloud). Astronomers don't bother comparing the density of the medium to that of liquid water, which weighs one gram per cubic centimeter (cc). Instead, they count the number of hydrogen atoms per cc. (For comparison, there are 700 billion billion hydrogen atoms in a cc of pure hydrogen gas at the pressure at Earth's surface). Frisch suggests that the vacuum-like interstellar medium may have promoted a stable atmosphere. "If the sun was being buffeted by a dense interstellar medium, it would probably affect our climate, although we don't know exactly how."

23. Interstellar Medium And Star Formation interstellar medium and Star Formation. The general goals of the research group can be formulated as follows. $\bullet$ To investigate the physical and http://www.astro.helsinki.fi/report/1998/node11.html

Next: Infrared studies with ISO: Up: Research Activities Previous: Research Activities Interstellar Medium and Star Formation The general goals of the research group can be formulated as follows: To investigate the physical and chemical propetrties of interstellar molecular clouds, especially the initial conditions for star formation , i.e. the temperature, density, radiation field and chemical composition. The radio spectroscopical studies performed by the group have been directed towards the following three main fields: 1) Dynamical processes and chemistry in nearby low-mass star forming regions 2) Physical properties and chemical composition of giant molecular cloud cores and their variation as a function of the galactocentric radius 3) Modeling of the structure of dense molecular clouds with the aid of Monte Carlo radiative transfer calculations of spectral line profiles and three-dimensional cloud models These three lines of investigation are interrelated and are instrumental to the understanding of the evolution of molecular clouds and the star formation process in general. To investigate the properties and composition of interstellar dust grains in dense and diffuse clouds, especially by means of the infrared emission and scattered radiation.

24. INTERSTELLAR MEDIUM AND STELLAR PHYSICS The study of the interstellar medium, with particular reference to the problems of chemistry, star formation and early stellar evolution, is one of the main http://www.arcetri.astro.it/pubblicazioni/GenReport/Rapp1996/node4.html

Next: EXTRAGALACTIC AND HIGH ENERGY Up: Title Page Previous: SUN AND SOLAR SYSTEM INTERSTELLAR MEDIUM AND STELLAR PHYSICS Contributors: V. Calamai, P. Caselli, R. Cesaroni, A. Falchi, M. Felli, D. Galli, C. Giovanardi, M. Landolfi, A. Natta, E. Oliva, F. Palla, S. Randich, A. Richichi, G. Torricelli-Ciamponi, R. Valdettaro, M. Walmsley INTERSTELLAR MEDIUM AND STAR FORMATION The study of the interstellar medium, with particular reference to the problems of chemistry, star formation and early stellar evolution, is one of the main fields of interest of the Arcetri community. In the following subsections, a brief outline is presented of the main observational and theoretical projects and results obtained during the last year. The IV Arcetri-Saclay-Grenoble meeting on Star Formation has taken place this year in Gif-sur-Yvette (Saclay, France) on September 9-10 and has been attended by a large number of researchers of this group. [ Light Element Abundances The work on the abundance of the light elements, in particular D and He, has been developed on both the theoretical and observational side. Current models of stellar evolution predict a production of

25. Interstellar Medium - Space And Astronomy Definition - Online Dictionary And Glo interstellar medium from an ever growing glossary of space and astronomy definitions. Find the definitions for interstellar medium and all your space and http://space.about.com/od/glossaries/g/interstellmed.htm

zGCID=" test0" zGCID=" test0 test6" zJs=10 zJs=11 zJs=12 zJs=13 zc(5,'jsc',zJs,9999999,'') You are here: About Education Space / Astronomy Astronomy and Space Basics ... Astronomy Dictionary interstellar medium - Space and Astronomy Definition - Online Dictionary and Glossary Definition of interstellar medium Space / Astronomy Education Space / Astronomy Essentials ... Submit to Digg Free Email Courses Space Tragedies 9 Planets in Nine Days Astronomy 101 Recent Discussions Stuff Race To Mars Race To Mars Recent Discussions Apollo 1 Fire Comet Man First Lady of Astronomy Most Popular Earth Globe Visual Tour of Solar System V838 Monocerotis Earth Pictures - A Growing Collection of Earth Pictures ... Neil Armstrong Biography "interstellar medium" From Nick Greene Your Guide to Space / Astronomy FREE Newsletter. Sign Up Now! Definition: interstellar medium: The gas and dust between stars, which fills the plane of the Galaxy much like air fills the world we live in. For centuries, scientists believed that the space between the stars was empty. It wasn't until the eighteenth century, when William Herschel observed nebulous patches of sky through his telescope, that serious consideration was given to the notion that interstellar space was something to study. It was only in the last century that observations of interstellar material suggested that it was not even uniformly distributed through space, but that it had a unique structure. Free Email Courses Space Tragedies 9 Planets in Nine Days Astronomy 101 Recent Discussions Stuff Race To Mars Race To Mars Recent Discussions

26. Solar Wind Interacting With Interstellar Medium This animation illustrates how the constant outflow of particles from the sun, called the solar wind, interacts with the surrounding interstellar medium http://techtv.mit.edu/file/449

PokkariPlayer.BARISTA_ENDPOINT = "http://barista.blip.tv:9393/barista/resolve"; Pokkari.siteUrl = "http://techtv.mit.edu"; Pokkari.imagesUrl = "http://static.blip.tv"; Learn about MIT TechTV and check out our resource page for media makers at MIT. Search: Solar wind interacting with interstellar medium File: Newsoffice-SolarWindInteractingWithInterstellarMedium519.flv Full-screen Play video in alternate format: Select a format Email Share Comment Close Email This to a Friend Let your friends and family know about this! Just tell us their e-mail addresses (we promise not to use them for anything but this e-mail ) and the e-mail address you'd like the message to come from. We'll take care of the rest. From: To: Message: Type the code above: This helps us prevent automated submissions. More information Close Share Solar wind interacting with interstellar medium Permalinks Blogging del.icio.us Flickr ... Social This post, including its media, can be accessed at the following URL: This post's media file can be accessed directly at the following URL:

27. [astro-ph/0702158] Transport Of Positrons In The Interstellar Medium Abstract This work investigates some aspects of the transport of lowenergy positrons in the interstellar medium (ISM). We consider resonance interactions http://arxiv.org/abs/astro-ph/0702158

arXiv.org astro-ph Search or Article-id Help Advanced search All papers Titles Authors Abstracts Full text Help pages Full-text links: Download: PostScript PDF Other formats Citations SLAC-SPIRES HEP (refers to , cited by , arXiv reformatted) NASA ADS CiteBase p revious ... ext Astrophysics Title: Transport of positrons in the interstellar medium Authors: W. Gillard P. Jean A. Marcowith K. Ferriere (Submitted on 6 Feb 2007) Abstract: This work investigates some aspects of the transport of low-energy positrons in the interstellar medium (ISM). We consider resonance interactions with magnetohydrodynamic waves above the resonance threshold. Below the threshold, collisions take over and deflect positrons in their motion parallel to magnetic-field lines. Using Monte-Carlo simulations, we model the propagation and energy losses of positrons in the different phases of the ISM until they annihilate. We suggest that positrons produced in the disk by an old population of stars, with initial kinetic energies below 1 MeV, and propagating in the spiral magnetic field of the disk, can probably not penetrate the Galactic bulge. Comments: 4 pages, 3 figures, accepted for publication in the proceeding of the 6th INTEGRAL workshop

28. Triggered Star Formation In A Turbulent Interstellar Medium (IAU S237) - Cambrid It summarizes the current state of understanding of triggered star formation in a turbulent interstellar medium. Topics covered range from observations and http://www.cambridge.org/catalogue/catalogue.asp?isbn=9780521863469

29. Interstellar Medium The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. Whilst the ISM refers to the http://www.sciencedaily.com/articles/i/interstellar_medium.htm

Science Reference Share Blog Print Email Bookmark Interstellar medium The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. See also: Astrophysics Nebulae Galaxies Stars ... Dark Matter Whilst the ISM refers to the matter (interstellar matter, also abbreviated by ISM) that exists between the stars within a galaxy, the energy, in the form of electromagnetic radiation, that occupies the same volume is called the interstellar radiation field (or ISRF). The ISM consists of an extremely dilute (by terrestrial standards) plasma, gas and dust, consisting of a mixture of ions, atoms, molecules, larger dust grains, electromagnetic radiation, cosmic rays, and magnetic fields. The matter consists of about 99% gas and 1% dust by mass. It fills interstellar space. This mixture is usually extremely tenuous, with typical gas densities ranging from a few hundred to a few hundred million particles per cubic meter. As a result of primordial nucleosynthesis, the gas is roughly 90% hydrogen and 10% helium by number, with additional elements ("metals" in astronomical parlance) present in trace amounts. The ISM plays a crucial role in astrophysics precisely because of its intermediate role between stellar and galactic scales. Stars form within the densest regions of the ISM, molecular clouds, and replenish the ISM with matter and energy through planetary nebulae, stellar winds, and supernovae.

30. The Interstellar Medium At Wisconsin An active program of research into the composition of the interstellar medium exists at the UWMadison Physics department. This includes efforts in both http://wisp.physics.wisc.edu/ism/ism.html

The Interstellar Medium An active program of research into the composition of the interstellar medium exists at the UW-Madison Physics department. This includes efforts in both theory and observation. ISM theory: Professor Don Cox heads the ISM Theory effort at Madison. His research interests are many,but his present work includes: modeling the Local Bubble surrounding our Solar System, modeling the evolution of supernova remnants, modeling spiral density waves as hydraulic jumps, to name only a few. Click on the picture to the right for further details on Don's interests and research. DXS- The Diffuse X-Ray Spectrometer The Diffuse X-ray Spectrometer instruments were flown on the STS-54 mission of the Space Shuttle Endeavour in January of 1993. DXS obtained the first-ever spectra of the diffuse soft x-ray background in the energy band from 0.15 to 0.284 keV (wavelength 42 to 84 Angstroms). SHS-The Spatial Heterodyne Spectrometer: This innovative class of Fourier Transform Spectrometer does not require mechanical scanning of mirrors or other components. A rocket-borne SHS instrument is being developed, with the goal of making an all-sky survey of emissions from the hot (100,000 K) component of the interstellar medium (ISM). The lines of interest, which act as tracers of the hot gas, are emitted by triply-ionized carbon, or CIV, in a doublet at 1548-1550 Angstroms. XQC-The X-Ray Quantum Calorimeter: On June 3rd, 1996, the X-ray Quantum Calorimeter was launched from White Sands Missle Range, New Mexico. This flight obtained the first high-resolution, wide-bandwidth spectrum of the ISM. The instrument consists of an array of 36 microcalorimeters which measure the heat deposited by individual x-rays. In order to work effectively, these detectors run at 60mK, making this the coldest payload ever launched into space.

31. MIS interstellar medium Modeling http://aristote.obspm.fr/MIS/

32. Interstellar Medium / Research @ CITA / CITA Stars and the interstellar medium are the two components of the Galaxy, and they have a close and intricate relationship. Stars form out of clouds of gas http://www.cita.utoronto.ca/index.php/research_cita/interstellar_medium

Featured Research Preprints Galaxies High Energy Astrophysics ... Computational Astrophysics Interstellar Medium Related CITA preprints Stars and the interstellar medium are the two components of the Galaxy, and they have a close and intricate relationship. Stars form out of clouds of gas and dust. Stellar radiation and winds, as well as supernova explosions, play crucial roles in sculpting the ISM. The Canadian Galactic Plane Survey, for which Martin serves as a scientific director, is conducting an HI and continuum radio survey at 1 arc minute resolution. Combined with other data sets with similar resolution, this provides an excellent resource for studying the interplay between stars and the ISM. Much of the ISM-related research at CITA focusses on the process of star formation. We know that stars form when dense "cores" within molecular clouds collapse under their own self-gravity, but the details of the collapse have not yet been elucidated. Magnetic fields appear to play an important role. Recent Related Preprints Molecular Cloud Evolution. II. From Cloud Formation to the Early Stages of Star Formation in Decaying Conditions

33. SEGway - About Exploring The Interstellar Medium Exploring The interstellar medium includes descriptions of interstellar medium and several handson activities. Within this unit, students will explore the http://cse.ssl.berkeley.edu/SEGwayed/abtintmedium.html

SEGway home SEGwayEd space science Exploring The Interstellar Medium Exploring The Interstellar Medium includes descriptions of Interstellar Medium and several hands-on activities. Within this unit, students will explore the science concepts of heat and temperature and the interactions between light and matter. Key Questions 1. What is interstellar medium? 2. What is the local bubble? 3. Why are matter and energy conserved between stars and interstellar medium? 4. What is the connection between interstellar medium and stars? Learning Objectives 1. Students will be able to use scientific experimentation to demonstrate why the sky is blue and to study the differences between heat and temperature. 2. Students will be able to calculate the volume of interstellar space in an average part of the galaxy. 3. Students will be able to name at least two ways the interstellar medium can be heated. 4. Students will be able to explain how interstellar medium is connected to the birth of stars. General Subject Areas Space Science Author: CSE @ SSL VIEW THE LESSON Student Activities The lesson starts with a review of interstellar medium. Students are encouraged to read the information given on the web and take note of the main ideas. Students answer review questions and attempt several math problems with the teacher. Students will then explore, through a lab activity, why the sky is blue and explore the differences between heat and temperature.

34. HEA Research:Hot Interstellar Medium HEA Research Hot interstellar medium. Normal spiral galaxies such as our own Milky Way contain immense volumes of very hot gas, with temperatures of http://cfa-www.harvard.edu/hea/eg/him.html

Contacts CfA Home HCO Home SAO Home ... Press Room Resources for . . . Scientists Software Users The Public CfA Staff HEA Research HEA Centers HEA Missions HEA Technology ... CfA Intranet HEA Research: Hot Interstellar Medium Normal spiral galaxies such as our own Milky Way contain immense volumes of very hot gas, with temperatures of millions of degrees. We are beginning to understand the sources and life cycle of this gas, heated by supernova explosions and the winds from young, hot stars. It is still not clear, for example, how this gas, rich in newly synthesized elements such as carbon, oxygen, and iron, cools and is recycled into future generations of stars and planets (e.g. in starbursts and galaxy mergers ). Gas at these temperatures is a potent source of x-rays, smoothly distributed over large areas of the sky. We have used Chandra and other x-ray observatories to survey our own and other galaxies for bubbles of hot gas. Teasing apart the foreground heliospheric x-ray emission from Galactic hot gas, and from extragalactic x-ray sources, is tricky, but can be approached due to the superb angular resolution of the Chandra X-ray Observatory. This hot gas fills voids in cooler gas, which can be seen in absorption with satellites such as HST and FUSE. Five-times ionized Oxygen in the boundaries of hot regions can be studied with FUSE, and combined with x-ray observations of six- and seven-times ionized oxygen to provide a more complete picture of the hot interstellar medium.

35. Astronomy 622: The Interstellar Medium Origin and fate of interstellar matter Mass loss stars, planetary nebulae, Supernovae, evolution and balance of interstellar medium http://www.ifa.hawaii.edu/gradprog/astro_622.htm

Astronomy Education - Site Map: Astronomy Education - Graduate Program - Undergraduate Education ... - 800: PhD dissertation Modified by JEB on May 30, 2007 Astronomy 622: The Interstellar Medium Overview of ISM : phases, properties of gas and dust, distribution of ISM Ionized gas: Stromgren spheres, partially ionized regions, recombination lines, free-free radiation, bound-free radiation, forbidden line emission, determining temperatures, densities and abundances in HII regions, thermal balance in HII regions, diffuse ionized gas, radio propagation effects. Neutral gas: the 21-cm line: interstellar abundances, diffuse interstellar bands, heating, cooling, instabilities and phases of ISM. Molecular gas: Interstellar chemistry, mm-wave emission, cloud models, typical properties of molecular clouds, interstellar masers. Interstellar dust: extinction, reddening, scattering, polarization, thermal equilibrium of dust grains, VSGs and PAH emission, size and nature of dust grains, origin and destruction mechanisms. Non-thermal phenomena: Interstellar magnetism cosmic rays, synchrotron emission, supernova remnants.

36. Interstellar Medium --  Britannica Online Encyclopedia Britannica online encyclopedia article on interstellar medium region between the stars that contains vast, diffuse clouds of gases and minute solid http://www.britannica.com/eb/article-9042624/interstellar-medium

var britAdCategory = "other"; Already a member? LOGIN Encyclopædia Britannica - the Online Encyclopedia Home Blog Advocacy Board ... Free Trial Britannica Online Content Related to this Topic This Article's Table of Contents interstellar medium Print this Table of Contents Linked Articles hydrogen radio telescopes infrared Shopping New! Britannica Book of the Year The Ultimate Review of 2007. 2007 Britannica Encyclopedia Set (32-Volume Set) Revised, updated, and still unrivaled. New! Britannica 2008 Ultimate DVD/CD-ROM The world's premier software reference source. interstellar medium Page 1 of 1 region between the stars that contains vast, diffuse clouds of gases and minute solid particles. Such tenuous matter in the interstellar medium of the Milky Way system, in which the Earth is located, accounts for about 5 percent of the Galaxy's total mass. The interstellar medium is filled primarily with hydrogen interstellar medium... (75 of 387 words) To read the full article, activate your FREE Trial Close Enable free complete viewings of Britannica premium articles when linked from your website or blog-post.

37. ICE - Molecular Astrophysics And Interstellar Medium Research Cosmology and Gravitation Galaxies Stellar Physics Molecular Astrophysics and interstellar medium High Energy Astrophysics http://www.ice.csic.es/en/research_area.php?areaId=3

38. Interstellar Medium@Everything2.com The interstellar medium (hereafter ISM) was first discovered in 1904, with the observation of stationary calcium absorption lines superimposed on the http://everything2.com/index.pl?node_id=1021468

39. Details For Interstellar Medium This site offers information about the interstellar medium. It discusses what the interstellar medium is, how it has developed, how astronomers know what http://www.astronomycenter.org/items/detail.cfm?ID=1064

40. The Local Interstellar Medium The Local interstellar medium. We turn now from a consideration of the most global aspect of the ISM to a consideration of its properties in the immediate http://praxis.pha.jhu.edu/papers/papers/afdscirev_b/node7.html

Next: Origin of Ultraviolet Up: Scientific Results Previous: The Galactic Corona The Local Interstellar Medium about K and number density around . This gas is highly ionized and therefore provides no opacity for observations within 100 pc or so. Numerous investigations have shown, however, that there is a minimum column density of neutral atomic hydrogen of about toward all stars observed, and this minimum is all that is seen for stars in the local bubble. Thus, it appears that the Sun must be surrounded by a small, at least partially neutral cloud with approximately this column density. An atomic-hydrogen density of about 0.1 cm and a bubble size of 3-5 pc are consistent with the existing data. There is completely independent evidence of partially neutral interstellar gas in the immediate vicinity of the Sun from observations of solar Lyman- in the gas flowing through the solar system and a neutral-hydrogen density about five times as large with a temperature of about 8,000 K. The low observed ratio of H to He compared with the nominal cosmic abundance ratio of 10 has usually been interpreted to indicate that the hydrogen is significantly ionized, whereas the helium is largely neutral. However, known sources of ionizing radiation in the solar neighborhood are insufficient to maintain such a high degree of hydrogen ionization in the local cloud. ). We found a hydrogen column density of

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