The Spiral-Arm Structure of the Milky Way Galaxy Has Been

question 53

Multiple Choice

The spiral-arm structure of the Milky Way Galaxy has been measured and evaluated MOST effectively by observations of

• A) globular clusters in the halo of the Galaxy.
• B) Balmer emission lines of visible radiation from hydrogen.
• C) 21-cm radiation from interstellar hydrogen and the distribution of young stars.
• D) Lyman UV radiation from hot hydrogen gas.

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Definitions:

Precipitation

The process by which water condenses from the atmosphere and falls to the earth's surface as rain, snow, sleet, or hail.

Transpiration

The process by which plants absorb water through the roots and give off water vapor through pores in their leaves.

Temperature Range

The variation between the minimum and maximum temperatures over a period of time or in a specific environment.

Precipitation

Any form of water - liquid or solid - that falls from clouds and reaches the ground, including rain, snow, sleet, and hail.