The detection and study of such line spectra would add considerably to present information on interstellar gas clouds and, perhaps, planetary atmospheres.

Results of this experiment include the frequencies of the two strong spectral lines by which OH may be identified in interstellar gas ; ;

It is believed that most of the stable beryllium in the universe was originally created in the interstellar medium when cosmic rays induced fission in heavier elements found in interstellar gas and dust.

The cyanide radical ( called cyanogen ) is used to measure the temperature of interstellar gas clouds.

Dark matter's existence is inferred from gravitational effects on visible matter and gravitational lensing of background radiation, and was originally hypothesized to account for discrepancies between calculations of the mass of galaxies, clusters of galaxies and the entire universe made through dynamical and general relativistic means, and calculations based on the mass of the visible " luminous " matter these objects contain: stars and the gas and dust of the interstellar and intergalactic medium.

A galaxy is a massive, gravitationally bound system consisting of stars, stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component called dark matter.

In between these objects is a sparse interstellar medium of gas, dust, and cosmic rays.

In 1944, Hendrik van de Hulst predicted microwave radiation at a wavelength of 21 cm resulting from interstellar atomic hydrogen gas ; this radiation was observed in 1951.

However, gravitational stripping of the interstellar gas and dust that makes up the spiral arms produces a long train of stars known as tidal tails.

A major issue with traveling at extremely high speeds is that interstellar dust and gas may cause considerable damage to the craft, due to the high relative speeds and large kinetic energies involved.

When a protostar is formed from the collapse of a giant molecular cloud of gas and dust in the local interstellar medium, the initial composition is homogeneous throughout, consisting of about 70 % hydrogen, 28 % helium and trace amounts of other elements, by mass.

Within our own galaxy, molecular gas accounts for less than one percent of the volume of the interstellar medium ( ISM ), yet it is also the densest part of the medium comprising roughly one-half of the total gas mass interior to the Sun's galactic orbit.

Many nebulae or stars form from the gravitational collapse of gas in the interstellar medium or ISM.

The interstellar medium of dust and gas from which stars form is primarily composed of hydrogen and helium with trace amounts of heavier elements.

Another possibility is that the star formed from an interstellar medium of gas and dust that was unusually metal-poor.

* Evaporating gaseous globule, a type of interstellar gas cloud that is thought to give rise to new stars, and known as an EGG.

The obvious fuel source, the one proposed by Bussard, is fusion of hydrogen, the most common component of interstellar gas.

# Sweeping up of a shell of shocked circumstellar and interstellar gas.

A spiral galaxy like the Milky Way contains stars, stellar remnants and a diffuse interstellar medium ( ISM ) of gas and dust.

An interstellar cloud of gas will remain in hydrostatic equilibrium as long as the kinetic energy of the gas pressure is in balance with the potential energy of the internal gravitational force.

In astronomy, the interstellar medium ( or ISM ) is the gas and cosmic dust that pervade interstellar space: the matter that exists between the star systems within a galaxy.

They can explain why chemistry is so prevalent in the interstellar medium, where many different polyatomic species have been detected ( by radio astronomy ), but where temperatures are so low that conventional wisdom might suggest that chemical reactions do not occur.

The low temperatures and densities of interstellar clouds would seem to imply that life processes would operate much more slowly there than on Earth.

Until recently the rates of reactions in interstellar clouds were expected to be very slow, with minimal products being produced due to the low temperature and density of the clouds.

Third, temperatures must be lower than those in stars ( elements are stripped of electrons: a plasma state ) but higher than in the interstellar medium ( reaction rates are too low ).

Some of these elements, particularly those lighter than iron, are thought to be delivered to the interstellar medium in the last stages of evolution of dying low mass stars, in the non-explosive ejection of the outer envelope gases of plantetary nebulae before these stars continue to form white dwarfs.

The products of stellar nucleosynthesis are generally distributed into the interstellar gas through mass loss episodes and stellar winds in stars of low mass, as in the photographically beautiful planetary nebulae phase of low-mass evolution, and through explosive events, called supernovae, in stars having more than eight times the mass of the sun.

Due to the prevalence of hydrogen in interstellar gas, and its relatively low energy of ionization, many emission nebulae appear red due to the strong emissions of the Balmer series.

* Facilitating the intercept of significant numbers of interstellar dust particles using the same collection medium, also at as low a velocity as possible.

Physicists showed in the 1920s that in gas at extremely low densities — even interstellar matter considered dense in an astronomical context is at high vacuum by laboratory standards — electrons can populate excited metastable energy levels in atoms and ions which at higher densities are rapidly de-excited by collisions.

Furthermore, there is very little interstellar matter ( neither gas nor dust ), which results in low rates of star formation, few open star clusters, and few young stars ; rather elliptical galaxies are dominated by old stellar populations, giving them red colours.

An interesting feature of M26 is a region of low star density near the nucleus, most likely caused by an obscuring cloud of interstellar matter between us and the cluster.

For example in the Space Empires series interstellar travel is only possible via " wormholes " and the running costs of fleets are fairly low, so turtlers treat some systems on the edge of their territory as choke point, keeping their fleets in these locations.

It has been speculated that these stars could have formed relatively recently in dwarf galaxies containing primordial metal-free interstellar matter ; past supernovae in these galaxies could have ejected their metal-rich contents at speeds high enough for them to escape the galaxy, keeping the metal content of the galaxy very low.

However, data from the Interstellar Boundary Explorer suggests that the velocity of the Sun through the interstellar medium is too low for a bow shock to form.

In space plasmas where the electron density is relatively low, the Debye length may reach macroscopic values, such as in the magnetosphere, solar wind, interstellar medium and intergalactic medium ( see table ):

However, even by using the significantly more sensitive Very Large Array, such a signal could not be detected, and the probability that a signal below the Very Large Array level could be detected by the Big Ear radio telescope due to interstellar scintillation is low.

This nearby explosion may be responsible for the low density of the interstellar medium in the immediate vicinity of the Solar System.

He has pursued a broad range of problems ranging from star formation to high energy physics, including the interactions of supernovae shocks with interstellar clouds, the formation of low and high mass stars, accretion onto neutron stars, and Compton-heated winds from accretion disks.

They differ greatly from the solids formed at low temperature within the interstellar medium.

It is stable in the interstellar medium ( ISM ) due to the low temperature and low density of interstellar space.