An Astronomer Measures the Rotation Speed of a Spiral Galaxy

question 30

Essay

An astronomer measures the rotation speed of a spiral galaxy.How can she use this to estimate the galaxy's distance?

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Definitions:

Pacemaker Cells

Specialized cells in the heart that control the heart rate by generating and conducting electrical signals.

Heart Rate

The number of heartbeats per unit of time, usually per minute, reflecting the speed at which the heart is beating and pumping blood through the body.

Inspiration

The process of drawing air into the lungs, or a sudden creative idea.

Expiration

The process of exhaling air out of the lungs, a key component of breathing.