What Is a Protoplanetary Disk

question 30

Multiple Choice

What is a protoplanetary disk?

• A) a disk of gas and dust, such as those observed around some stars in the Orion nebula
• B) a disk of debris around a planet of greater mass than Jupiter, material from which rings and moons will form
• C) a disk of debris orbiting an exoplanet, for example, the planet orbiting the star 51 Pegasi
• D) a disk of cold debris orbiting far from a star, such as the Oort cloud of our solar system

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Definitions:

Marginal Social Cost

The total cost to society of producing one additional unit of a good, including both private costs and externalities.

Equilibrium Price

The price at which the quantity of a product offered for sale equals the quantity of that product in demand.

Air Cargo

Goods being transported by aircraft, often for commercial purposes or rapid delivery.

Pollutants

Substances or objects that cause pollution, negatively affecting air, water, or soil quality.