The Sun holds 99.86% of the system's mass; the eight planets are leftovers from the protoplanetary disk. Orbital speed ratios stay true to life, and only when the compressed spacing gives way to real spacing does it become clear how far out Neptune actually sits. Every planet hides a different interior: Mercury's iron core fills 83% of its radius, while Venus spins backwards and has a day longer than its year.
The Sun holds 99.86% of the system's mass; the eight planets are leftovers from the protoplanetary disk. Orbital speed ratios stay true to life, and only when the compressed spacing gives way to real spacing does it become clear how far out Neptune actually sits. Every planet hides a different interior: Mercury's iron core fills 83% of its radius, while Venus spins backwards and has a day longer than its year.
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