Uncovering Icy Objects in the Kuiper Belt

Hubble’s discoveries helped NASA plan the New Horizon spacecraft’s flyby of Pluto and beyond.

Three views of Pluto. Three mottled circles in colors of yellow, grey, rusty-orange, and black.

While probing the dwarf planet Pluto on the outskirts of our solar system, Hubble spied four previously unknown moons orbiting the icy world. The tiny moons Nix and Hydra were the first to be spotted, followed by the even tinier Kerberos and Styx. Astronomers later discovered that Nix and Hydra are rotating chaotically – that is, unpredictably – as they orbit the dwarf planet.

Hubble Discoveries - Pluto Moons
Hubble discovered Pluto’s four small moons, Nix, Hydra, Styx, and Kerberos. This is a composite of two images of the Pluto system taken by Hubble in July 2012. The blue areas are from a long exposure used to capture the tiny outer moons, but which greatly oversaturated Pluto and Charon. The dark central vertical band is from a shorter exposure designed to show Pluto and Charon more clearly. The diameters of Pluto and its moons are not to scale.
NASA, ESA, and M. Showalter (SETI Institute)

NASA’s New Horizons spacecraft shot past Pluto in July 2015, making detailed observations of its surprisingly varied and intriguing surface. Hubble played a critical role in helping astronomers prepare for the flyby. With frequent observations of Pluto from the early 1990s to 2010, scientists refined maps of the dwarf planet’s surface. New Horizons personnel used these maps to prepare for the spacecraft’s brief but important rendezvous with Pluto and its moons.

Hubble observations of Pluto, mapped over spheres
Hubble’s view of Pluto provided NASA’s New Horizons mission with the best available information for planning its rendezvous with the dwarf planet.
NASA, ESA and M. Buie (Southwest Research Institute)

Peering out even farther, to the dim outer reaches of our solar system, Hubble uncovered two Kuiper Belt objects that the New Horizons spacecraft could potentially target on its continual outward journey. The New Horizons mission chose to focus on a Hubble candidate called 2014 MU69. On Jan. 1, 2019, New Horizons flew past the object – now named Arrokoth – capturing up-close imagery that revealed its double-lobed structure in fine detail, complete with fractures and pitting.

Hubble's view of the first moon discovered around dwarf planet Makemake
Only about 100 miles in diameter, the tiny dot above the dwarf planet Makemake seen in this Hubble image is its orbiting moon, nicknamed MK 2.
NASA, ESA, and A. Parker and M. Buie (SwRI)

Hubble also discovered a 100-mile-wide moon in orbit around Makemake, the second-brightest icy dwarf planet in the Kuiper Belt. At 4.8 billion miles from the Sun, Makemake was discovered in 2005 using the Palomar Observatory and is approximately 870 miles across. Oddly, the moon, nicknamed MK 2, is as dark as charcoal while Makemake is as bright as fresh snow.

Hubble Discovers Moon Orbiting Dwarf Planet Makemake Credit: NASA's Goddard Space Flight Center; Producer: Katrina Jackson

Explore Other Hubble Science Highlights

Learn about some of Hubble's most exciting scientific discoveries.

Cepheid star in Andromeda galaxy (Hubble observations)

Discovering the Runaway Universe

Our cosmos is growing, and that expansion rate is accelerating.

Hubble Ultra Deep Field image

Tracing the Growth of Galaxies

Hubble is instrumental in uncovering the various stages of galactic evolution.

Hubble image left to right: Jupiter, Uranus, Saturn, Neptune

Studying the Outer Planets and Moons

Hubble’s systematic observations chart the ever-changing environments of our solar system's giant planets and their moons. 

Hubble view of an expanding halo of light around star v838 monocerotis

Seeing Light Echoes

Like ripples on a pond, pulses of light reverberate through cosmic clouds forming echoes of light.

Hubble observations of galaxies' centers

Monster Black Holes are Everywhere

Supermassive black holes lie at the heart of nearly every galaxy.

Hubble observations of Carina Nebula section

Exploring the Birth of Stars

Hubble’s near-infrared instruments see through the gas and dust clouds surrounding newborn stars.

An oval of colorful tendrils of gas and dust stretching from lower-left to upper right. Ova's outer ring is rusty-red tendrils, followed by a yellow/lime-green ring of tendrils. Oval's center is bright turquoise with white tendrils bisecting it. All set on a black background.

The Death Throws of Stars

From colliding neutron stars to exploding supernovae, Hubble reveals details of some of the mysteries surrounding the deaths of stars. 

depiction of gravitational lensing

Shining a Light on Dark Matter

Hubble’s observations help astronomers uncover the underlying structure of the universe.

Thirty proplyds in a 6 by 5 grid. Each one is unique. Some look like tadpoles, others like bright points in a cloudy disk.

Finding Planetary Construction Zones

Hubble’s sensitivity can reveal great disks of gas and dust around stars.

Comma shaped curved cloud of gases in bright white edged with bright-pink star forming regions, and threaded with rusty-brown tendrils of dust at center and throughout the comma shaped merger. All set against the black of deep space.

Galaxy Details and Mergers

Hubble’s observations reveal a menagerie of galaxies.

Blue background. Center of image is a disk blocking the light of a star. Below and just to the left of the disk, at about seven o'clock, is a bright white point. This is PDS 70b.

Recognizing Worlds Beyond Our Sun

Hubble’s unique capabilities allow it to explore planetary systems around other stars. 

animation of a binary asteroid with a shifting tail

Tracking Evolution in the Asteroid Belt

These conglomerates of rock and ice may hold clues to the early solar system.