Solar system · Question

What is an astronomical unit?

An astronomical unit (au) is a defined unit of length: exactly 149,597,870,700 metres (about 150 million km), close to the typical distance between Earth and the Sun. It's a convenient ruler for solar system distances, but hard to picture. Pick a real-world step size and see where every planet would actually be.

Visual model

If 1 AU were this long, where would Neptune be?

Or set 1 AU = cm

Mercury29 cm

Venus54 cm

Earth75 cm

Mars1.1 m

Jupiter3.9 m

Saturn7.2 m

Uranus14.4 m

Neptune22.5 m

Dot positions use a log scale so every planet stays visible; the distances printed above each dot are the real linear numbers at your chosen scale.

01 / A journey you can walk

Travel the distance, not the planet sizes.

The scale is linear. If one AU is your step, Neptune's orbit is about 22.5 metres down this imaginary path. The travel animation speeds up the walk; it does not represent spacecraft speed.

0.00 AU0.00 m from the Sun at your chosen scale

Position on the real linear distance ruler 0.00 AU

At the Sun. Pick a planet or drag the ruler to jump directly to its average orbital distance. Orbit positions and planet body sizes are not to scale.

Scene design reference: NASA/JPL Solar System Size and Distance. All orbital values are average AU distances, not live positions. This camera journey is an illustration, not a mission trajectory.

Apply AU · 2026

How far is the newly found dwarf-planet candidate?

2026 ED138 was roughly 46 AU from the Sun when announced; its orbital semimajor axis is 43.09 AU. Those are different measures. Use this AU model, then explore ED138's discovery and uncertain size ↗.

Measurable fact