The Kuiper Belt

The Kuiper Belt is a doughnut-shaped region of icy objects beyond the orbit of Neptune. It is home to Pluto and most of the known dwarf planets and some comets.

This artist's impression is of NASA's New Horizons spacecraft encountering Arrokoth, a Kuiper Belt object that orbits one billion miles (1.6 billion kilometers) beyond Pluto, on Jan. 1, 2019.

Kuiper Belt Overview

The Kuiper Belt is a doughnut-shaped region of icy bodies extending far beyond the orbit of Neptune. It is home to Pluto and Arrokoth. Both worlds were visited by NASA's New Horizons spacecraft. There may be millions of other icy worlds in the Kuiper Belt that were left over from the formation of our solar system. Scientists call these worlds Kuiper Belt objects (KBOs), or trans-Neptunian objects (TNOs). Trans-Neptunian objects are objects in our solar system that have an orbit beyond Neptune.

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Similar to the asteroid belt, the Kuiper Belt is a region of leftovers from the solar system's early history. Like the asteroid belt, it has also been shaped by a giant planet, although it's more of a thick disk (like a donut) than a thin belt.

The Kuiper Belt shouldn't be confused with the Oort Cloud, which is a much more distant region of icy, comet-like bodies that surrounds the solar system, including the Kuiper Belt. Both the Oort Cloud and the Kuiper Belt are thought to be sources of comets.

The Kuiper Belt is truly a frontier in space – it's a place we're still just beginning to explore and our understanding is still evolving.

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Illustration of spacecraft near a giant space rock far from the Sun.

Hubble Finds Smallest Kuiper Belt Object

NASA’s Hubble Space Telescope has discovered the smallest object ever seen in visible light in the Kuiper Belt

Hubble observations of nearby stars show that a number of them have Kuiper Belt-like disks of icy debris encircling them. These disks are the remnants of planetary formation. Researchers surmise that over billions of years the debris should collide, grinding the KBO-type objects down to ever smaller pieces that were not part of the original Kuiper Belt population.

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Artist's view of the smallest Kuiper Belt object
An illustration of the smallest Kuiper Belt Object.
NASA, ESA and G. Bacon

Hubble Follows Shadow Play Around Planet-Forming Disk

The young star TW Hydrae is playing “shadow puppets” with scientists observing it with NASA’s Hubble Space Telescope

In 2017, astronomers reported discovering a shadow sweeping across the face of a vast pancake-shaped gas-and-dust disk surrounding the red dwarf star. The shadow isn’t from a planet, but from an inner disk slightly inclined relative to the much larger outer disk – causing it to cast a shadow. One explanation is that an unseen planet’s gravity is pulling dust and gas into the planet’s inclined orbit.

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Artists concept: 3 concentric rings of dust and gas. At center: a glowing sphere. Reddish-colored rings inclined to each other due to gravity of unseen planets warping the disk, casting shadows across the outermost ring at 11 o'clock and 12 o'clock.
This illustration is based on Hubble Space Telescope images of gas-and-dust disks around the young star TW Hydrae.
NASA, AURA/STScI for ESA, Leah Hustak (STScI)
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NASA’s New Horizons to Continue Exploring Outer Solar System

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