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:

Embryonic Development

The series of biological changes that occur in the early stages of an organism's life, leading to its mature form.

Blastocyst

An early stage of embryonic development in mammals, characterized by a sphere of cells surrounding a fluid-filled cavity and the inner cell mass that will develop into the embryo.

Blastula

An early stage in embryonic development in animals, characterized by a sphere of cells (blastomeres) surrounding a fluid-filled cavity (blastocoel).

Embryonic Development

The process by which an embryo forms and develops, from the fertilization of the ovum to the fetal stage of development.