Planets and Orbits

Water in vapor form

Found in objects that orbit closer to the Sun.

Water in solid form

Found in objects that orbit further from the Sun.

Orbital period

The time it takes for a planet to complete one revolution around the Sun.

Direct relationship

As one variable increases, the other variable increases.

Indirect/inverse relationship

As one variable increases, the other variable decreases.

Cyclic relationship

As one variable increases, the other variable increases and decreases over and over.

Constant relationship

As one variable increases, the other remains the same.

Kepler's First Law

Planets orbit the Sun in elliptical orbits with the Sun at one focus.

Kepler's Second Law

Equal area in equal time; a planet travels faster when closer to the Sun.

Kepler's Third Law

The square of a planet's orbital period is directly proportional to the cube of the semi-major axis of its orbit.

Aphelion

The point farthest from the Sun in the orbit.

Perihelion

The point closest to the Sun in the orbit.

Centrifugal force

The force that causes a planet to want to fly off in a straight line.

Gravitational attraction

The force that pulls a planet toward the star it orbits.

Transit method

A technique used to determine if an exoplanet is orbiting a star by measuring light dimming.

Eccentricity

A measure of how oval or circular an orbit is.

Diameter

The size of the planet.

Length of year

The time it takes for a planet to complete one revolution around the Sun.

Length of day

The time it takes for a planet to complete one rotation on its axis.

Average distance from the Sun

The mean distance of a planet from the Sun during its orbit.

Triangulation

A method of drawing a planet's orbit by measuring angles from different positions.

Habitable zone

The region around a star where conditions may be suitable for life.