Why Is 21-Cm Radiation the Best Way to Map the Spiral

question 9

Multiple Choice

Why is 21-cm radiation the best way to map the spiral arms in the Milky Way?

• A) The molecular hydrogen gas that produces this emission is concentrated in the spiral arms.
• B) These photons, which are produced by neutral hydrogen, pass through the dense clouds of gas and dust in the disk.
• C) The emission is produced by supernovae, which are concentrated in the spiral arms.
• D) Radio telescopes are easier to operate than optical telescopes, and observations can be made even during the daytime.
• E) Radio photons do not have Doppler shifts, so we can detect clouds of gas without having to worry about the orbital velocities.

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Definitions:

Stagnation

A state of inactivity or lack of progress and development, often used in psychological contexts to describe periods of life where growth is perceived to halt.

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The total amount of skeletal muscle in an individual's body, crucial for physical strength and overall health.

Extra Pounds

A term often used to refer to additional weight that a person carries, typically considered to be beyond what is healthy or normal for their body type and height.

Weights

Measures of the force of gravity acting on an object, commonly used in the context of physical objects or body mass.