inner planet
noun
: any of the planets Mercury, Venus, Earth, and Mars whose orbits are within the asteroid belt
Examples of inner planet in a Sentence
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Evidence that rocky planets beyond Jupiter formed as rapidly, and at the same time, as the inner planets could transform our understanding of how planets take shape — not only in our solar system, but in planetary systems throughout the universe, the researchers said.
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Samantha Mathewson, Space.com, 21 July 2025
Earth orbits the sun at more than 30 km/s, so firing a probe at the sun or the inner planets is extremely hard because of all that sideways velocity.
—Phil Plait, Scientific American, 19 June 2025
But there’s more to it than that: the spacecraft can actually use the planet’s gravity to speed up or slow down after this maneuver, allowing easier voyages to the outer or inner planets, respectively.
—Phil Plait, Scientific American, 19 June 2025
Understanding ‘Greatest Western Elongation’ This moment is the planet's greatest western elongation, which is when one of the inner planets — Mercury and Venus — reaches its maximum apparent separation west of the sun.
—Jamie Carter, Forbes.com, 29 May 2025
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Samantha Mathewson, Space.com, 21 July 2025
Earth orbits the sun at more than 30 km/s, so firing a probe at the sun or the inner planets is extremely hard because of all that sideways velocity.
—Phil Plait, Scientific American, 19 June 2025
But there’s more to it than that: the spacecraft can actually use the planet’s gravity to speed up or slow down after this maneuver, allowing easier voyages to the outer or inner planets, respectively.
—Phil Plait, Scientific American, 19 June 2025
Understanding ‘Greatest Western Elongation’ This moment is the planet's greatest western elongation, which is when one of the inner planets — Mercury and Venus — reaches its maximum apparent separation west of the sun.
—Jamie Carter, Forbes.com, 29 May 2025
See All Example Sentences for inner planet
Cite this Entry
“Inner planet.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/inner%20planet. Accessed 2 Aug. 2025.
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