On a logarithmic scale — every step rightward is 10× farther from the Sun — because the real distances are otherwise impossible to draw on one page. All eight planets sit in the bright strip on the left; the belts and reservoirs stretch far beyond. Tap a region.
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Between Mars and Jupiter, roughly 2.1 to 3.3 AU from the Sun, orbit more than a million rocky bodies larger than a kilometre. Yet their total mass is only about 4% of the Moon's — the belt is mostly empty space, nothing like the crowded rubble of the movies. A third of that mass is a single object, the dwarf planet Ceres (940 km).
No planet formed here because Jupiter's gravity kept stirring the region, so the material never coalesced. That same influence carves Kirkwood gaps — near-empty lanes at distances where an asteroid's orbit would resonate with Jupiter's (the 3:1 gap at 2.50 AU, 5:2 at 2.82, 2:1 at 3.28). Sharing Jupiter's own orbit, 60° ahead and behind, sit the Trojan asteroids, trapped in stable gravitational parking spots.
Beyond Neptune, from about 30 to 50 AU, lies a second, colder, far larger belt of icy bodies — the Kuiper belt, home to Pluto and thousands of known "KBOs". Its "classical" members (nicknamed cubewanos) orbit calmly at 42–48 AU. Others are locked in resonance with Neptune: the plutinos, including Pluto itself, circle exactly twice for every three Neptune orbits (a 3:2 resonance at 39.4 AU), which protects them from ever colliding with the giant that shepherds them.
This is the reservoir that feeds short-period comets like Halley. NASA's New Horizons flew past Pluto in 2015 and the KBO Arrokoth in 2019, revealing worlds far more varied than anyone expected.
A dwarf planet orbits the Sun and is round under its own gravity, but has not cleared its orbital neighbourhood of other bodies. The IAU officially recognises five: Ceres (in the asteroid belt) and four out in the Kuiper region — Pluto (2,377 km), Eris (2,326 km, whose 2005 discovery triggered Pluto's reclassification), Makemake and Haumea (an egg-shaped world spinning end-over-end every four hours).
Many more are near-certain dwarf planets awaiting formal status: Gonggong, Quaoar, Orcus ("the anti-Pluto"), and the remote Sedna. Estimates suggest the outer solar system may hold hundreds.
Past the Kuiper belt, gravity has flung objects onto steeply tilted, wildly stretched orbits — the scattered disc. Some, like Eris, dip in near Neptune (30–40 AU) at perihelion; these Neptune could plausibly have scattered.
But a handful of detached / extreme trans-Neptunian objects (ETNOs) never come close enough for Neptune to have moved them: Sedna stays beyond 76 AU even at its nearest and swings out to ~937 AU; 2012 VP113 and Leleākūhonua are similar. What could have lifted their orbits so far from the planets?
One striking clue: several of the most extreme of these orbits appear to point the same way in space. In 2016 Batygin and Brown argued this clustering could be the gravitational fingerprint of an unseen "Planet Nine" — perhaps 5–10 Earth masses, orbiting hundreds of AU out. It remains unconfirmed and debated: as of 2026 the Vera C. Rubin Observatory has begun a systematic search that could settle the question within a couple of years (astronomers put the odds of a find, if it exists, at 70–80%), while newly found bodies such as the June 2026 sednoid 2023 KQ14 ("Ammonite"), whose orbit is misaligned with the cluster, actually weaken the original evidence. No one has yet seen it.
The Sun blows a supersonic wind of charged particles that inflates a vast bubble around the whole planetary system — the heliosphere. Around 90 AU the wind abruptly slows at the termination shock; near 120 AU it finally gives way to true interstellar space at the heliopause. This is the edge of the Sun's wind — but not of its gravity.
Only two spacecraft have ever crossed it: Voyager 1 (in 2012) and Voyager 2 (in 2018), launched back in 1977 and still faintly calling home. Right now Voyager 1 is about … and Voyager 2 about … from the Sun, each receding a further ~3.5 and ~3.1 AU every year.
Far beyond everything else, a spherical shell of perhaps trillions of icy bodies is thought to surround the Sun from roughly 2,000 out to 100,000 AU — the Oort cloud. Unlike the flat belts, it wraps the solar system in every direction. It is the source of the long-period comets that fall in on million-year orbits, occasionally nudged loose by a passing star or the tide of the galaxy itself.
The Oort cloud has never been directly observed — we infer it entirely from where these comets come from. Its outer edge, held only weakly by the Sun's gravity, reaches perhaps a third of the way to the nearest star, Proxima Centauri (268,000 AU). This — not Neptune, not the heliopause — is the true gravitational edge of the Sun's domain.