The Shell of a Planetary Nebula Is Measured by the Doppler

question 263

Multiple Choice

The shell of a planetary nebula is measured by the Doppler shift of emission lines to be expanding outward at a speed of 10⁴ m/s,while its radius is measured to be 1 ly,or about 10¹⁶ m.Roughly how long has the shell been expanding? (Hint: 1 year = 3.15 × 10⁷ sec.)

• A) 30 years
• B) 30,000 years
• C) 30 million years
• D) 10¹² years

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Definitions:

Mnemonic Device

A Mnemonic Device is a learning technique that aids information retention by associating complex information with simple, easily recallable cues.

LEARN

An acronym that typically stands for Listen, Explain, Acknowledge, Recommend, and Negotiate, often used in educational and medical communication strategies.

Moral Distress

Occurs when the individual knows the ethically correct action to take but is unable to take the action because of internal or external barriers.

Ethics Rounds

A discussion within healthcare settings focusing on ethical dilemmas and moral problems arising in clinical practice.