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Articles related to: Interstellar Medium and Light  Read article

1. Interstellar Reddening  Read article

In addition to the absorption of starlight and re-emission at much longer wavelengths due to the cold temperature of the dust grains, interstellar grains can scatter light by absorbing a photon and then reemitting it in a different direction. Scattering off dust grains is more efficient at shorter ...

2. Composition of the Interstellar Medium  Read article

The interstellar medium contains primarily gas, atoms and molecules, and microscopic dust grains. The gas and dust grains are very cold because for the most part they’re far from sources of stellar radiation or heat sources. The interstellar gas was first discovered in 1904 by German astronomer Jo...

3. Interstellar Extinction  Read article

When starlight interacts with interstellar dust grains, the grains absorb ultraviolet and optical radiation and reemit in the infrared. They reemit at longer wavelengths because the grains are cool, ten or twenty degrees Kelvin. The result is a dimming of starlight at all optical wavelengths that ...

4. Interstellar Grain  Read article

Interstellar grains or dust grains are substantially larger than the molecules in interstellar space. Interstellar grains make up about one percent of the mass of the interstellar medium; however, there’s only one interstellar grain for every trillion hydrogen atoms or molecules. They range in siz...

5. Molecules in the Interstellar Medium  Read article

With the first detection in 1940, dozens of molecules have now been detected in the interstellar medium. Most of these molecules involve the elements carbon, nitrogen, oxygen, and hydrogen, the life elements. The most important astrophysically are molecular hydrogen, H2, and carbon monoxide, CO, b...

6. Emission Lines  Read article

Atoms lose energy by emitting photons. Since the energy levels in an atom are quantized and have particular values, the energy gained or lost by an atom also is a specific set of quantities, and this means that the spectral lines or emission lines from an atom that loses energy have a fixed set of ...

7. Polarization  Read article

A third effect of the interstellar medium on starlight is polarization. Light from stars far from the Sun has linear polarization imprinted on it at a very low level, usually fractions of a percent. This polarization is not due to the stars themselves but happens somewhere along the line of sight ...

8. Spectral Bands  Read article

Atoms produce sharp spectral features of emission or absorption corresponding to the specific energy states of the atom. Each element has its own set of energy states. Atoms that are grouped into molecules have a much larger set of possible energy states, in part because they share electrons and i...

9. Example of Effects of Interstellar Medium  Read article

All of the effects of gas and dust in the interstellar medium on starlight can be illustrated with the simple example of a young hot star with a gas cloud off to one side. If this star is viewed directly then the stellar spectrum shows clearly the atmosphere of the star, and the continuum reflects ...

10. Planetesimals  Read article

The collapse of the solar nebula creates a young star with a surrounding disk of gas and dust. Condensation takes us from molecules and groups of molecules to dust grains about a millimeter or so across. These grains are rocky in the inner solar system and primarily icy in the outer solar system. ...