Term
| Interstellar gas is composed mainly of |
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Definition
| 90% hydrogen, 9% helium by weight |
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Term
| What happens to light passing through an even thin clouds of dust? |
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Definition
| It dims and reddens the light of all more distant stars |
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Term
| Which statement about dark dust clouds is true? |
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Definition
| They can be penetrated only with longer wavelengths like radio and infared |
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Term
| Some regions along the milky way appear dark because |
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Definition
| stars in that region are hidden by dark dust particles |
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Term
| Emission nebulae like M42 occur only near stars that emit large amounts of |
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Definition
|
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Term
| What is the primary visible color of an emission nebula? |
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Definition
| red due to ionized hydrogen atms |
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Term
| Due to absorption of shorter wavelengths by interstellar dust clouds, distant stars appear |
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Definition
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Term
| The spectra of interstellar gas clouds show that they have the same basic composition as |
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Definition
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Term
| Which statement is true about the interstellar medium? |
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Definition
| We know more about the gas than the dust |
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Term
| The density of interstellar dust is very low yet it still blocks starlight because |
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Definition
| the dust particles are about the same size as teh light waves they absorb |
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Term
| What two things are needed to create an emission nebulae? |
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Definition
| hot stars and interstellar gas, particularly hydrogen |
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Term
| A large gas cloud in the interstellar medium that contains several type O and B stars would appear to us as |
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Definition
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Term
| Neutral hydrogen atoms are best studied from their energy given off as |
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Definition
| 21-cm waves in the radio region |
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Term
| Complex molecules in the interstellar medium are found |
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Definition
| primarily in the dense dust clouds |
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Term
| Why are dark dust clouds largely misnamed? |
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Definition
| they contain more gas than dust |
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Term
| THe average temp of the typical dark regions in space are |
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Definition
|
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Term
| When an electron in hydrogen changes its spin from the same to the opposite direction as the proton, it |
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Definition
| emits a radio wave photon |
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Term
| Interstellar dust clouds are best ovserved at what wavelength |
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Definition
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Term
| Which of these is not a consqeunce of dust in the interstellar medium |
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Definition
| red light from the emission nebulae |
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Term
| It is important to study interstellar dust because |
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Definition
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Term
| Reflection nebula have their blue colour because |
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Definition
| the interstellar dust deflects the blue light |
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Term
| What is true of emission nebula |
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Definition
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