Planetary Motion and Gravitation

Front

Planetary Motion Noun

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[plan-i-ter-ee moh-shun]

Back

Planetary Motion

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The movement and orbits of planets as they revolve around a central body, such as the Sun.

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Example: This diagram shows Earth's elliptical orbit around the Sun, a key part of planetary motion, highlighting the closest (Perihelion) and farthest (Aphelion) points.

Front

Gravitation Noun

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[grav-i-tey-shun]

Back

Gravitation

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A universal force of attraction that exists between any two objects possessing mass, pulling them toward each other.

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Example: This diagram shows that gravitation is a force that pulls objects from all directions toward the center of a massive planet like Earth.

Front

Astronomy Noun

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[uh-stron-uh-mee]

Back

Astronomy

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The scientific study of celestial objects, outer space, and the physical universe in its entirety.

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Example: This diagram shows the planets of our solar system orbiting the Sun, which is a central concept in astronomy and an example of planetary motion.

Front

Ellipse Noun

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[ih-lips]

Back

Ellipse

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A regular oval shape, characterized by two foci, which describes the path of a planet's orbit around the Sun.

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Example: The Earth's path around the Sun is not a perfect circle but an elongated, oval shape called an ellipse, with the Sun at one focus.

Front

Focus (Foci) Noun

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[foh-kus (foh-sahy)]

Back

Focus (Foci)

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One of two fixed points within an ellipse that determines its shape; the Sun occupies one focus in a planet's orbit.

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Example: This diagram shows an ellipse has two special points inside called foci. A planet's orbit is an ellipse, and the star it orbits is at one of these foci.

Front

Period Noun

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[peer-ee-ud]

Back

Period

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The specific amount of time required for an orbiting object to complete one full revolution around another central body.

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Example: This diagram shows the Moon's orbit around the Earth. The orbital period is the time it takes for the Moon to complete one full circle.

Front

Comet Noun

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[kom-it]

Back

Comet

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A celestial body composed of ice and dust that travels in a highly elliptical orbit around the Sun.

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Example: A comet is a celestial body of ice and dust that follows a long, elliptical orbit around the Sun, developing a tail as it gets closer.

Front

Gravitational Force Noun

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[grav-i-tey-shun-ul fors]

Back

Gravitational Force

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The mutually attractive force between two objects, which is directly proportional to the product of their masses.

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Example: This image shows that two objects with mass, like the Earth and another celestial body, pull on each other with an equal and opposite gravitational force.

Front

Centripetal Acceleration Noun

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[sen-trip-i-tl ak-sel-er-ey-shun]

Back

Centripetal Acceleration

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The acceleration experienced by an object moving in a circular path, which is always directed toward the center of the circle.

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Example: An object moving in a circle has a velocity (blue arrow) tangent to the path, but its acceleration (red arrow) always points toward the center.

Front

Universal Gravitational Constant (G) Noun

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[yoo-ni-vur-suhl grav-i-tey-shun-ul kon-stunt]

Back

Universal Gravitational Constant (G)

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The fundamental physical constant in Newton's law of universal gravitation, used to relate mass and distance to gravitational force.

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Example: This diagram shows that the Universal Gravitational Constant (G) is the specific value used in the formula for calculating the gravitational force between two masses.