A Wonderleaf question
Why is Pluto not a planet anymore?
a real page from the book
Pluto is not counted as a main planet now because it has not cleared the icy objects from its path around the Sun. In 2006, astronomers decided a planet must orbit the Sun, be rounded by gravity, and be dominant in its orbit.
Pluto still matters. It belongs to the Kuiper Belt, a faraway zone filled with frozen worlds, and it is rounded enough to be called a dwarf planet. The change was about our naming rules, not about Pluto disappearing.
Wonder words
- orbit
- gravity
- dwarf
- kuiper
Try it out
Line up small objects as a solar system, then add extra “icy worlds” near Pluto to show why its neighborhood is crowded.
Read the whole picture book
Watercolour scenes, straight answers, about three minutes cover to cover.
Open the picture bookOne more wonder: Why is space so dark?
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