AMSCO Chapter 2 Astronomy and Planetary Motion Vocabulary

Comprehensive question-and-answer flashcards covering key planetary motion, orbital mechanics, eclipse, and celestial terminology from AMSCO Chapter 2.

What does the term 'annular' mean when describing a solar eclipse?

It describes a ring-shaped eclipse in which the Moon does not obscure the entire solar disk, resulting in a bright ring of light around the Moon.

What is apoapsis?

The point in an orbit where an object is farthest from the body it is orbiting.

What is meant by apparent motion?

The way celestial objects appear to move across the sky.

What is axial tilt and what effect does it have?

The angle between a planet's rotational axis and its orbital plane, which affects seasons.

How is eccentricity defined regarding an ellipse?

The degree of elongation of an ellipse.

What is an eclipse?

An alignment of two celestial objects that causes one object to cast its shadow on the other.

What is the equator?

The imaginary line that circles Earth halfway between the North and South Poles.

What happens during an equinox?

Occurring at two moments during Earth's orbit (late March and September), the Sun is directly above the equator and everywhere on Earth receives approximately $12\,\text{hrs}$ of daylight, marking the beginning of spring and autumn.

What is a focus in geometry and Earth science?

Either of two fixed points that determine the shape and position of an ellipse, or an earthquake's point of origin within Earth.

What characterizes a gibbous Moon?

A phase of the Moon where more than half, but not all, of the Moon is illuminated.

How is gravity defined?

The attractive force between objects that is directly proportional to their masses and inversely proportional to the distance between them.

What is high tide and what causes it?

The twice-daily change in tide level when the water level is at its highest point, occurring due to the gravitational pull of the Moon on the oceans.

What is inertia?

The tendency of an object to remain at rest, or, if it is moving, to move at a constant speed in an unchanging direction.

What does Kepler's 1st Law state?

Planets move in elliptical orbits around the Sun, with the Sun located at one of the two foci of the ellipse, meaning that the distance between a planet and the Sun varies throughout its orbit.

What does Kepler's 2nd Law state about a planet's speed?

A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time during its orbit, meaning that a planet moves faster when it is closer to the Sun and slower when it is farther away.

What relationship is defined by Kepler's 3rd Law?

For any two planets orbiting the Sun, the square of the ratio of their orbital periods equals the cube of the ratio of their average distances from the Sun, meaning that the farther a planet is from the Sun, the longer it takes to complete one orbit.

What does Newton's law of universal gravitation state?

Every mass in the universe attracts every other mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

What is low tide?

The twice-daily change in tide level when the water level is at its lowest point, occurring due to the gravitational pull of the Moon on the oceans.

What is a lunar eclipse?

The alignment of Earth and the Moon in which Earth lies between the Moon and the Sun and casts its shadow on the Moon.

What is the major axis of an ellipse?

The line through the widest part of an ellipse.

What is the minor axis of an ellipse?

The line through the center of an ellipse that is perpendicular to the major axis.

What is a neap tide?

A tide that occurs during first and third quarter moons, when the Sun partially reduces the effect of the Moon's gravity, resulting in the smallest differences between high and low tide levels.

How is an orbit defined?

The path (usually an ellipse) of any satellite around its central body.

What causes orbital motion?

The movement of an object in a curved path around another object resulting from the balance between the gravitational force between them and inertia.

What is the penumbra?

The outer, lighter part of a shadow cast by an object, such as during an eclipse, where only a portion of the light source is obscured.

What is periapsis?

The point in an orbit where an object is closest to the body it is orbiting.

What causes a lunar phase?

The changing shape of the Moon as seen from Earth, which changes cyclically due to its position relative to Earth and the Sun.

What is a primary in orbital mechanics?

The central body located at a focus of an ellipse around which a satellite moves, such as the Sun to Earth or Earth to the Moon.

What is a satellite?

Any artificial or natural celestial object that moves around a central body.

What is a solar eclipse?

The alignment of Earth and the Moon in which the Moon lies between Earth and the Sun and casts its shadow on Earth.

What occurs during a solstice?

Either of two moments during Earth's orbit (late December and June) when one pole tilts farthest from the Sun and the other tilts closest, causing the longest and shortest days of the year and marking the beginning of summer and winter.

What causes a spring tide and what is its effect?

A tide that occurs when the Sun, the Moon, and Earth are aligned, resulting in the highest high tides and the lowest low tides due to their combined gravitational pull.

What is syzygy?

An alignment of $3$ celestial bodies, such as the Sun, Earth, and Moon, in a straight line, which gives rise to events like eclipses and new or full moons.

What is the umbra?

The darkest part of a shadow, where the light source is completely blocked.

What do the terms 'wax' and 'wane' mean in astronomy?

'Wax' means to increase in intensity (as when the illuminated portion of the Moon grows), whereas 'wane' means to decrease in intensity (when the visible portion of the Moon decreases).