Step by Step
1
The mnemonic itself
Each word's first letter matches a planet in order from the Sun: My (Mercury), Very (Venus), Educated (Earth), Mother (Mars), Just (Jupiter), Served (Saturn), Us (Uranus), Nachos (Neptune).
2
Terrestrial vs. gas/ice giants
Terrestrial (rocky) planets: Mercury, Venus, Earth, Mars — small, dense, in the inner solar system. Gas/ice giants: Jupiter and Saturn (gas), Uranus and Neptune (ice giants, composed mostly of water, ammonia, and methane).
3
What officially counts as a planet
According to the IAU's 2006 definition, a planet must (1) orbit the Sun, (2) be spherical due to its own gravity, and (3) have cleared its orbital neighborhood of other debris.
4
Dwarf planets and small-body regions
Pluto was reclassified as a dwarf planet in 2006 for failing criterion 3. Other dwarf planets include Eris, Ceres, Makemake, and Haumea. The asteroid belt sits between Mars and Jupiter; the Kuiper Belt lies beyond Neptune.
Applied Walkthrough
1
Using the mnemonic "My Very Educated Mother Just Served Us Nachos," you can recall all eight planets in order outward from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
2
The first four (Mercury through Mars) are terrestrial — small, rocky, and dense. The last four (Jupiter through Neptune) are gas or ice giants — much larger and far less dense.
3
Pluto, once considered the ninth planet, is now classified as a dwarf planet because — while it orbits the Sun and is spherical — it hasn't cleared its orbital neighborhood of other Kuiper Belt Objects, failing the third IAU criterion.
4
This same criterion is why Ceres (in the asteroid belt) and Eris (beyond Pluto) are also classified as dwarf planets rather than full planets, despite being roughly spherical and orbiting the Sun.
Exam Application
Exams test whether you can recite the planets in correct order, correctly classify each as terrestrial versus gas/ice giant, and apply all three parts of the IAU's planet definition to explain why Pluto is a dwarf planet.
⚠ Common Trap
The most common trap is thinking Pluto lost its planet status simply because of its small size — the actual disqualifying factor is specifically that it hasn't cleared its orbital neighborhood (criterion 3), not its size or shape.
✓ Quick Self-Check
1. What are the eight planets in order from the Sun?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
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2. Which four planets are terrestrial (rocky)?
Mercury, Venus, Earth, Mars.
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3. What are the three IAU criteria for a planet?
Orbits the Sun, is spherical due to its own gravity, and has cleared its orbital neighborhood.
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4. Why was Pluto reclassified as a dwarf planet?
It failed to clear its orbital neighborhood — criterion 3 of the IAU definition.
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5. Name two other dwarf planets besides Pluto.
Any two of: Eris, Ceres, Makemake, Haumea.
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