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Topic: Interstellar medium

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In the News (Thu 25 Apr 19)

  The Interstellar Medium
Approximately 99% of the mass of the interstellar medium is in the form of gas with the remainder primarily in dust.
Interstellar dust grains are typically a fraction of a micron across (approximately the wavelength of blue light), irregularly shaped, and composed of carbon and/or silicates.
One important probe of the interstellar medium is the distribution of the radioactive isotope aluminum-26.
csep10.phys.utk.edu /astr162/lect/milkyway/ism.html   (1215 words)

 Interstellar medium - Wikipedia, the free encyclopedia
In astronomy, the interstellar medium (or ISM) is the matter (interstellar matter, also abbreviated by ISM) and energy (interstellar radiation field, ISRF) content that exists between the stars within a galaxy.
The medium is also responsible for extinction and reddening, the decreasing light intensity and dominant observable wavelengths of a star as the light travels through the medium.
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).
en.wikipedia.org /wiki/Interstellar_medium   (946 words)

 ASTR 103: Interstellar Medium
Interstellar matter is not uniformly spread throughout the Galaxy but is clumped together in interstellar clouds that vary in size and the complexity of their association in our Galaxy.
Throughout that part of the interstellar medium that has been studied, the abundances of the chemical elements that are heavier than helium are similar generally to what they are in the Sun and other stars.
Some of the organic interstellar molecules have not yet been produced in a chemistry laboratory, so that study of the interstellar medium is adding a new dimension to organic chemistry.
www.physics.gmu.edu /~jevans/astr103/CourseNotes/Text/Lec24_interstellarMedium.htm   (6662 words)

 Nat' Academies Press, Exploration of the Outer Heliosphere and the Local Interstellar Medium: A Workshop Report (2004)
Exploration of the Outer Heliosphere and the Local Interstellar Medium: A Workshop Report 1 Introduction One remarkable, and to some extent unexpected, outcome of the Voyager mission is that after the Jovian and Saturnian encounters, the science that Voyager was accomplishing became as much the science of the interstellar medium as of the solar wind.
Interstellar space is a largely unknown frontier that, along with the Sun as the source of the solar wind, determines the size, shape, and variability of the heliosphere, the first and outermost shield against the influence of high-energy cosmic rays.
The interstellar medium is the cradle of the stars and planets, and its physical state and composition hold clues to understanding the evolution of matter in our galaxy and the universe.
www.nap.edu /openbook.php?record_id=11135&page=4   (1589 words)

 Interstellar medium   (Site not responding. Last check: 2007-09-17)
The interstellar medium (or ISM) is a term used in astronomy to describe the rarefied gas and that exists between the stars (or their immediate "circumstellar" environment) within galaxy.
The interstellar medium is usually divided into phases depending on the temperature of the hot (millions of Kelvin) warm (thousands of Kelvin) and cold of Kelvin).
The Dense Interstellar Medium in Galaxies: Proceedings of the 4th Cologne-Bonn-Zermatt-Symposium "The Dense Interstellar Medium in Galazies" Zermatt,...
www.freeglossary.com /Interstellar_matter   (534 words)

 ESA Human Spaceflight | Users » Interstellar Medium
Besides abundant hydrogen and helium, 114 interstellar and circumstellar gaseous molecules are currently identified in the interstellar medium, see Figure 2.
The incorporation of interstellar matter in meteorites and comets in the pre-solar nebula (as evidenced by isotopic measurements) provides the basis of the cosmic dust connection.
A comparison of interstellar and cometary ices using recent ISO data have revealed important similarities between interstellar ices and volatiles measured in the coma of some comets.
www.spaceflight.esa.int /users/index.cfm?act=default.page&level=1f&page=eanaistm   (430 words)

Determine the interstellar spectra of galactic cosmic rays and their contribution to the ionization, heating, and dynamics of the interstellar medium.
Study the deflection of the subsonic solar wind and interstellar plasma flows in the heliosheath, including the effects of thermal pressure gradients, magnetic fields, and the neutral interstellar gas.
Interstellar dust is, of course, eventually melted, sublimated, or evaporated by solar radiation as it falls into the Sun.
science.nasa.gov /ssl/pad/solar/suess/Interstellar_Probe/ISP-Intro.html   (1489 words)

 The Interstellar Medium
interstellar atoms are excited to very high levels from which they are ionized; when the ionization occurs, lines are formed in the ultraviolet.
The observational evidence for the existence of neutral hydrogen in the interstellar medium is
The principal effect(s) of interstellar dust on starlight is (are)
nas.cl.uh.edu /blanford/ASTR3131SQIMedium.htm   (459 words)

 What is the interstellar medium?
Approximately 99% of the interstellar medium is composed of interstellar gas, and of its mass, about 75% is in the form of hydrogen (either molecular or atomic), with the remaining 25% as helium.
The interstellar gas consists partly of neutral atoms and molecules, as well as charged particles, such as ions and electrons.
Interstellar dust is not like the dust that you might find under your bed; it is made of very different substances.
www-ssg.sr.unh.edu /ism/what1.html   (745 words)

 "INTERSTELLAR MEDIUM" related terms, short phrases and links
The interstellar medium is the material which fills the space between the stars.
Astrophysics; interstellar medium in gamma-ray-burst and high-redshift galaxies, the intergalactic medium.
Describes the gas and dust components of the interstellar medium in ionized regions, atomic clouds, and molecular clouds.
www.keywen.com /en/INTERSTELLAR_MEDIUM   (418 words)

 Zoom Astronomy Glossary: I
Interstellar dust is not at all like the dust we have in our houses (which is mostly bits of organic debris and lint).
The interstellar medium is the dust and gas (mostly hydrogen) that are between stars in a galaxy.
The interstellar medium is no very dense at all; at its densest, it is emptier than the best vacuum we can produce on Earth.
www.enchantedlearning.com /subjects/astronomy/glossary/indexi.shtml   (1189 words)

 Interstellar Medium: Hot   (Site not responding. Last check: 2007-09-17)
This is due to the fact that the density distribution of the interstellar medium is lumpy.
If the interstellar medium is dense, or the past supernova rate is small, then the interstellar medium has isolated bubbles of hot gas.
If the interstellar medium is thin, or the supernova rate is high, then the interstellar medium becomes filled with connect bubbles or tunnels of hot gas.
zebu.uoregon.edu /~js/ast122/lectures/lec24.html   (616 words)

 Interstellar Medium: Cold
Maps of interstellar reddening demonstrated that the interstellar medium is composed mostly of hydrogen and helium gas (99%) and traces of dust.
Radiation from interstellar molecules is a good tracer of the dense, thick regions of the interstellar medium.
We divide the interstellar medium into three types dependent on their temperature (called the phase of the interstellar medium): cold (10's K), warm (100 to 1000's K), hot (millions K).
abyss.uoregon.edu /~js/ast122/lectures/lec22.html   (1441 words)

 Voyager - Mission - Interstellar Mission
The mission objective of the Voyager Interstellar Mission (VIM) is to extend the NASA exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun's sphere of influence, and possibly beyond.
Penetration of the heliopause boundary between the solar wind and the interstellar medium will allow measurements to be made of the interstellar fields, particles and waves unaffected by the solar wind.
The first feature to be encountered by a spacecraft as a result of this interstellar wind/solar wind interaction will be the termination shock where the solar wind slows from supersonic to subsonic speed and large changes in plasma flow direction and magnetic field orientation occur.
voyager.jpl.nasa.gov /mission/interstellar.html   (893 words)

 The Interstellar Medium
Although the mass of the interstellar medium is not known with certainty, the ISM has at least enough matter to make billions of stars like our Sun.
Although the interstellar medium has an average density of about 1 atom for every cubic centimeter, the distribution of atoms is far from uniform.
And aside from being the home of a fascinating variety of astronomical objects, the interstellar medium serves as a type of "chemical recycling center" for stars.
lep694.gsfc.nasa.gov /lepedu/terms/ism.htm   (624 words)

The Interstellar Probe Mission would be designed to cross the solar wind termination shock and heliopause and make a significant penetration into nearby interstellar space in the direction the heliosphere is moving through the local interstellar medium (LISM).
Once beyond the heliopause Interstellar Probe would make direct measurements of properties of interstellar gas, dust, and the interstellar magnetic field, and of low-energy cosmic rays unaffected by the processes of “solar modulation” that shield the inner heliosphere.
Direct measurements would be made of the composition of interstellar dust, and of the elemental and isotopic composition of the ionized and neutral components of the interstellar gas and low-energy particle components, including key isotopes such as 2H, 3He, 13C, and heavier species.
science.msfc.nasa.gov /ssl/pad/solar/suess/Interstellar_Probe/ISP-MissionTech.html   (1046 words)

 Interstellar medium   (Site not responding. Last check: 2007-09-17)
The interstellar medium (or ISM) is a term used in astronomy to describe the rarefied gas and dust that exists between the star s (or their immediate "circumstellar" environment) within a galaxy.
Features prominent in the study of the interstellar medium include molecular cloud s, interstellar cloud s, supernova remnant s, planetary nebula e, and similar diffuse structures.
December 1, 2004: Big Medium 1.3.5 is an important security update that is recommended for all customers of the Big Medium web content management system.
www.serebella.com /encyclopedia/article-Interstellar_medium.html   (1252 words)

 Interstellar Medium   (Site not responding. Last check: 2007-09-17)
Astronomers believe that the cluster is currently moving through an interstellar cloud and...
Like many of the molecular species that have been detected in the interstellar medium, the singlet carbene cyclopropenylidene (C 3 H 2) has been presumed to...
is a strong possibility for the following reasons: (i) hydrogen and nitrogen are among the most abundant gaseous species in the interstellar medium and nascent...
www.wikiverse.org /interstellar-medium   (411 words)

About one percent of the mass of the interstellar medium is in the form of solid (frozen) material called interstellar dust or grains or sometimes cosmic dust.
We see interstellar absorption lines of CH, CH+ and CN but the big breakthrough in interstellar chemistry came in 1963 when the hydroxyl radical OH was detected after the characteristic frequencies were firmly established in the laboratory.
We see the interstellar medium is far from uniform, but we expect that the ISM strives for pressure equilibrium so the hot regions are rarified and the cold regions dense.
www.physics.uq.edu.au /people/ross/phys2080/ism/ism.htm   (3482 words)

While the Sun's radiation is obvious, the other components of the interplanetary medium were not discovered until very recently.
The temperature of the interplanetary medium is about 100,000 K. Its density is about 5 particles/cm3 near the Earth and decreases by an inverse square law farther from the Sun.
The Ulysses spacecraft is conducting an extensive study of the Sun and the solar wind.
seds.lpl.arizona.edu /nineplanets/nineplanets/medium.html   (509 words)

 According to an interstellar medium...
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).
Since the position of the heliopause depends on the balance between the strength of the flow of interstellar medium and the strength of the solar wind, if the interstellar medium gets much denser, it could shrink the heliopause significantly.
If the heliopause shrinks to inside Earth's orbit, our planet would be exposed directly to the interstellar medium, possibly causing an increase in cosmic rays at the top of the atmosphere, a decrease in ultraviolet radiation, and other changes that could affect the atmosphere, weather and life in unpredictable ways.
whyfiles.org /017planet/gas_cloud2.html   (574 words)

 At what speed does the interstellar medium become lethal to high speed flight?
Interstellar space also contains a few microscopic dust grains (micron-sized is common) in a region about a few meters on a side.
At 50 percent the speed of light which is the minimum for interstellar travel you will cover enough distance in a short amount of time, that your liklihood of encountering a large interstellar dust grain becomes significant.
But the situation could well be worse than this if the interstellar medium contains lots of ice globules from ancient comets and other things we cannot begin to detect in interstellar space.
www.astronomycafe.net /qadir/q2720.html   (709 words)

 ESA Science & Technology: The Interstellar Heliopause Probe   (Site not responding. Last check: 2007-09-17)
The main focus is on heliospheric physics in the outer heliosphere and local interstellar medium.
The main scientific objective of the IHP is to investigate the interface region between the local interstellar medium and the heliosphere and to truly reach the interstellar medium at 200 AU.
To reach the interstellar medium in the shortest possible time the spacecraft will have to be launched in the direction of the heliosphere nose, which is located at 7.5° latitude and 254.5° longitude, in the ecliptic coordinate frame.
sci.esa.int /science-e/www/object/index.cfm?fobjectid=36022   (826 words)

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