inner planet

[ in-er plan-it ]

noun

, Astronomy.

1. any of the planets in our solar system whose orbits lie between the sun and the asteroid belt, namely, Mercury, Venus, Earth, and Mars, all of which are terrestrial planets.

inner planet

noun

1. any of the planets Mercury, Venus, earth, and Mars, whose orbits lie inside the asteroid belt

inner planet

1. Any of the four planets Mercury, Venus, Earth, and Mars, whose orbits lie nearest the Sun. The inner planets are of similar size and have high densities compared to the larger gas giants among the outer planets. They are composed mostly of rock and metal and are relatively slow to rotate, with solid surfaces, no rings, and few moons.
2. Also called terrestrial planet
3. Compare outer planetSee also inferior planet

Word History and Origins

Origin of inner planet¹

First recorded in 1950–55

Example Sentences

The orbits of the three known planets showed a 3/2 resonance between each neighboring pair: For every three times the inner planet orbits, the outer neighbor orbits twice.

From Science Magazine

The exoplanets are huge: the inner planet is 14 times as massive as Jupiter and the outer one is 6 times as massive.

From Nature

But get around these and the view, at least, might be pleasing to the eye: wispy clouds, a giant red sun, and an inner planet that rises like Venus.

From The Guardian

How a small inner planet stays on that path as a bigger planet lurches on an elliptical orbit around the same star is a mystery.

From Scientific American

How the small inner planet could stay on that path as a bigger planet lurches on an elliptical orbit around the same star is a mystery.

From Nature