Pluto is not the last object in the Solar System, and the Kuiper Belt is not a neat outer wall. Beyond Neptune lie thousands of known icy bodies, a much larger population still waiting to be found, the scattered disc, the Sun's enormous bubble of solar wind, and — much farther out — the still hypothetical Oort Cloud.
There is no single universally useful line where the Solar System finishes and everything else begins. The answer depends on whether we mean the end of the planets, the end of the Sun's particle environment, or the furthest objects still held by the Sun's gravity. Space has, rather inconsiderately, declined to install a boundary fence.
| Neptune | about 30 AU from the Sun |
| Main Kuiper Belt | roughly 30–50 AU |
| Pluto | about 30–49.3 AU; mean about 39 AU |
| Scattered disc | overlaps the Kuiper Belt and can extend to nearly 1,000 AU |
| Heliopause | not spherical or fixed; Voyagers crossed it at about 119–121 AU |
| Oort Cloud | thought to begin thousands of AU out and extend perhaps to 100,000 AU |
| 1 AU | the mean Earth–Sun distance: about 150 million km / 93 million miles |
Planetary edge: beyond Neptune we leave the realm of the eight major planets, but not the Solar System.
Heliospheric edge: at the heliopause the outward solar wind can no longer dominate the surrounding interstellar medium. Voyager 1 and Voyager 2 have crossed this boundary.
Gravitational edge: objects in the distant Oort Cloud can still orbit the Sun, placing the Sun's gravitational family enormously farther out than the heliopause.
In other words: “interstellar space” does not necessarily mean “outside the Solar System” if we are talking about gravitationally bound objects.
A normal linear diagram becomes almost useless here: once the Oort Cloud is included, the inner planets would be crushed into a few pixels beside the Sun. The scale below is therefore logarithmic. Equal distances across the graphic represent powers of ten rather than equal numbers of astronomical units.
On the enormous scale above, even our most distant spacecraft are still clustered close to the Sun. So here is the same idea on a much smaller, linear scale. The subdued markers show their approximate positions 5 and 10 years ago, the hollow gold markers preserve their position on 12 August 2026, the solid pale markers show where they are approximately now, and the remaining markers project another 10, 25 and 50 years ahead.
The main Kuiper Belt begins around Neptune's orbit, roughly 30 AU from the Sun, and its main population extends to about 50 AU. It is not an asteroid belt copied farther out: many of its bodies contain large amounts of water, methane, ammonia and other volatile ices left from the early Solar System.
Pluto is one member of this population. Other large trans-Neptunian worlds include Eris, Haumea and Makemake, while New Horizons gave us our first close look at a much smaller Kuiper Belt object when it flew past Arrokoth in 2019.
Beyond and overlapping the main belt is the scattered disc. Its objects can travel on much more elongated and inclined orbits, reaching hundreds of AU from the Sun; NASA describes the scattered disc as extending to nearly 1,000 AU, with some objects travelling even farther.
The Sun continuously blows out the solar wind: charged particles carrying the Sun's magnetic field into space. This creates the heliosphere, a vast bubble embedded in the local interstellar medium.
The important boundaries are not perfect spheres. They move and deform as solar activity changes and as the heliosphere interacts with the gas, dust and magnetic field between the stars. Voyager 1 crossed the heliopause in 2012 at roughly 121 AU from the Sun; Voyager 2 crossed a different part of it in 2018 at roughly 119 AU.
Voyager 1 and Voyager 2 are the only spacecraft to have crossed the heliopause. Voyager 1 did so in August 2012 and Voyager 2 in November 2018. Both continue to operate in the local interstellar medium, returning measurements from a region no other functioning spacecraft has reached.
Voyager 1 remains the most distant human-made object. In November 2026 it is expected to become the first spacecraft to reach a distance from Earth equal to one full light-day — more than 16 billion miles away.
That sounds comfortably beyond the Solar System until the Oort Cloud is brought into the argument. On that much larger gravitational scale, the Voyagers have barely begun the outward journey.
The Oort Cloud is thought to be an enormous, roughly spherical swarm of icy bodies surrounding the planetary system. Unlike the Kuiper Belt, it has never been observed directly as a structure. Its existence is inferred largely from the behaviour of long-period comets and from models of Solar System formation.
Estimates are necessarily broad. NASA gives the inner edge as somewhere around 2,000–5,000 AU from the Sun and the outer edge somewhere between about 10,000 and 100,000 AU. At the largest estimates it stretches a substantial fraction of the way to the nearest stars.
Voyager 1 will not reach even the inner Oort Cloud for roughly another three centuries, and traversing the whole region could take tens of thousands of years. Human beings have sent machinery into interstellar space, but on the scale of the Sun's gravitational realm we are still very close to home.
After Pluto in 2015 and Arrokoth in 2019, New Horizons continued through the Kuiper Belt. It emerged from a 321-day hibernation in June 2026 in good health and is continuing measurements of dust, charged particles and the outer heliosphere.
In July 2026 NASA reported it was about 5.9 billion miles (9.5 billion km) from Earth.
Launched in 1977, both spacecraft are now beyond the heliopause and continue the Voyager Interstellar Mission.
They are outside the Sun's solar-wind bubble, but nowhere near the putative outer edge of the Oort Cloud.
The outer Solar System is one of those subjects where every apparent edge reveals another much larger structure behind it. These NASA pages are useful starting points for current mission and distance information.