Reality → Scale → Macro world → Solar system

Solar system

The Sun is circled by 8 planets and millions of smaller bodies (down to the size of pebbles and dust) in the Asteroid and Kuiper belts. Generally, the elliptical orbits of the planets deviate less than 5% from a circle and are less than 4 degrees inclined to the Earth's orbit (only Mercury's orbit is more elliptical and more inclined). The orbital periods range from 88 days for Mercury to 165 years for Neptune. The Sun diameter is about 100 times the Earth diameter (i.e. the Sun volume equals a million Earth volumes). The distance from Sun to Earth (defined as the astronomical unit or au) equals about 110 Sun diameters. The distance from Sun to Neptune, the last planet, equals about 30 au. Doubling the distance to Neptune, we arrive at the outer fringe of the Kuiper Belt ^[1] . But the Sun's gravitational pull does not stop there. The distance to the farthest reaches of the Oort cloud, assumed home of long-period comets, may be in the ballpark of 100,000 au, which is still less than halfway from the Sun to the nearest star ^[2] .

If we imagine the Sun as a golf ball in the center of a stadium, Neptune would orbit at the outer rim of the stadium; shrinking Neptune's orbit to the size of the golf ball, the stadium rim would represent the boundary of our solar system.

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