interstellar gas

astronomy

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June 29, 2026

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Interstellar gas, also known as the interstellar medium, refers to the tenuous clouds of gas and dust found in space between stars. This matter primarily consists of hydrogen and helium, with trace amounts of other elements. Interstellar gas is not uniformly distributed; it exists in various forms, including H II regions (ionized hydrogen), H I regions (neutral hydrogen), and molecular clouds (hydrogen in molecular form). These clouds can be incredibly dense and cold, serving as the birthplaces of new stars. Conversely, extremely hot, low-density gas is produced by supernovae. Interstellar dust within these clouds plays a crucial role, absorbing and scattering starlight, which can make distant stars appear dimmer and redder.12345678

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chemical element
Stars and gas clouds
…to stars, the Galaxy contains interstellar gas and dust. Some of the gas is very cold, but some forms hot clouds, the gaseous nebulae, the chemical composition of which can be studied in some detail. The chemical composition of the gas seems to resemble that of young stars. This is…
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…to stars, the Galaxy contains interstellar gas and dust. Some of the gas is very cold, but some forms hot clouds, the gaseous nebulae, the chemical composition of which can be studied in some detail. The chemical composition of the gas seems to resemble that of young stars. This is…
Read More

Milky Way Galaxy
The general interstellar medium
The dust is accompanied by gas, which is thinly dispersed among the stars, filling the space between them. This interstellar gas consists mostly of hydrogen in its neutral form. Radio telescopes can detect neutral hydrogen because it emits radiation at a wavelength of 21 cm. Such radio wavelength is long…
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The dust is accompanied by gas, which is thinly dispersed among the stars, filling the space between them. This interstellar gas consists mostly of hydrogen in its neutral form. Radio telescopes can detect neutral hydrogen because it emits radiation at a wavelength of 21 cm. Such radio wavelength is long…
Read More

molecular cloud
Composition
Molecular clouds consist mainly of gas and dust but contain many stars as well. The central regions of these clouds are completely hidden from view by dust and would be undetectable except for the far-infrared thermal emission from dust grains and the microwave emissions from the constituent molecules. This radiation…
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Molecular clouds consist mainly of gas and dust but contain many stars as well. The central regions of these clouds are completely hidden from view by dust and would be undetectable except for the far-infrared thermal emission from dust grains and the microwave emissions from the constituent molecules. This radiation…
Read More