Term
| What is interstellar medium (ISM)? |
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Definition
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Term
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Definition
| dark, dense, molecular clouds of dusty gas that form in darkest, densest parts of ISM |
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Term
| Within the Milky Way, for how much of the ISM volume do molecular clouds account? |
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Definition
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Term
| For how much of the total gas mass interior of the Sun's galactic orbit do molecular clouds account? |
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Definition
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Term
| How can we determine the composition of interstellar gas? |
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Definition
| From its absorption lines in the spectra of background stars |
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Term
| What is the composition (% and elements) of interstellar gas in the Milky Way? |
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Definition
| 70% Hydrogen, 28% Helium, 2% heavier elements |
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Term
| Does the rotation speed increase or decrease as the cloud contracts, and what does this do to the cloud? |
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Definition
| increases, leads to flattening of cloud |
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Term
| What is the precondition for planet formation? |
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Definition
| As the outskirts of the disk cool, planets will begin to form, but without rotation, they will fall directly into the star |
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Term
| Thought Question: What would happen to a protostar that formed without any rotation at all? |
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Definition
| It would not have planets. |
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Term
| With what are protostellar jets aligned and what does that indicate? (text) |
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Definition
| They are aligned with disk's rotation axis, indicating that angular momentum plays a large role (p 521) |
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Term
| What do promising models rely on for explaining the jets? (text) |
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Definition
| The jets rely on magnetic fields to link angular momentum of protostar's disk to outflowing gas in jet. Magnetic field lines passing through disk get twisted into rope-like configuration by disk's rotation; this twisted field may help channel jets of charged particles along axis (p 521-2) |
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