Pluto

Pluto, once considered the ninth and most distant planet from the sun, is now the largest known dwarf planet in the solar system. It is also one of the largest known members of the Kuiper Belt, a shadowy zone beyond the orbit of Neptune thought to be populated by hundreds of thousands of rocky, icy bodies each larger than 62 miles (100 kilometers) across, along with 1 trillion or more comets.  

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Pluto, as seen by NASA’s New Horizons spacecraft during its flyby of the dwarf planet in July 2015.

New Horizons Pluto probe notches 3 new discoveries in outer solar system

By Sharmila Kuthunur published

NASA's New Horizons probe flew by Pluto nearly eight years ago, but the epic encounter is still bearing scientific fruit.

Artwork of the dwarf planet Pluto (left) and its largest moon Charon.

Cracks on Pluto's moon Charon may be evidence of a frozen subsurface ocean

By Robert Lea published

The icy volcanism of Pluto's moon Charon may be driven by an internal frozen ocean erupted through a thin shell.

close up of pluto with rippled terrain and an ice cap visible below

Why is Pluto not a planet?

By Adam Mann, Elizabeth Howell published

Reference Pluto, officially a dwarf planet, has surprising complexity on its surface. While certainly a world, not everyone agrees it is a planet.

Titanic expedition patch reading "Titanic: the Ultimate Dive 2022. 110th anniversary."

Pluto explorer deep dives to the Titanic

By Leonard David published

For planetary scientist Alan Stern, witnessing the 20th century deep sea sarcophagus that is the Titanic serves up analogies to spaceflight.

Pluto against the black background of space. The planet is a mix of colors from dark blood-red to white and a dusting of yellow at the top. In the lower right side of the image, the large white expanse of the Tombaugh Regio takes the shape of a heart.

Pluto: Everything you need to know about the dwarf planet

By Charles Q. Choi, Scott Dutfield published

Reference Pluto was once considered the ninth planet in the solar system, it was demoted in 2006 to dwarf planet status. We explore this icy body in more detail here.

Starry Night

Dim Pluto reaches its brightest as the third-quarter moon meets Mars in the night sky

By Elizabeth Howell published

Here's how to observe these solar system worlds overnight Wednesday (July 20) and Thursday (July 21).

Pluto, as seen by NASA’s New Horizons spacecraft during its flyby of the dwarf planet in July 2015.

Far beyond Pluto: What's next for NASA's New Horizons probe?

By Leonard David last updated

New Horizons is still on duty in extended mission mode, diving ever deeper into the Kuiper Belt to examine ancient, icy mini-worlds in that vast region beyond the orbit of Neptune.

Charon beauty shot

Pluto's moon Charon sports a red polar cap that forms as seasons change

By Keith Cooper published

The red cap on Pluto's moon Charon results when ultraviolet light and the solar wind interact with hydrocarbons and turn them into a soup of organic compounds dubbed tholins.

A collage shows a New Horizons image of Pluto against a space background.

Curious Kids: Why does it matter if Pluto is a planet or a dwarf planet?

By Samantha Lawler published

"Comet," "star" and "planet" are category names that immediately tell you something important about what they describe.

Sand blown by wind into ripples within Victoria Crater at Meridiani Planum on Mars, as photographed by NASA’s Mars Reconnaissance Orbiter on October 3, 2006.

What's it like to be on Venus or Pluto? We studied their sand dunes and found some clues.

By Andrew Gunn published

What is it like to be on the surface of Mars or Venus? Or even further afield, such as on Pluto, or Saturn's moon Titan?

Pluto, as seen by NASA's New Horizons spacecraft in 2015.

How Pluto walks a tightrope between a stable and chaotic orbit

By Keith Cooper published

Pluto is lucky to exist in the orbit that it does, according to new computer simulations that show how the dwarf planet skirts near a chaotic orbit that could potentially destroy the beloved world.

Pluto, the largest of the dwarf planets. This image was taken by NASA’s New Horizons spacecraft.

Curious kids: What is a dwarf planet?

By Vahe Peroomian published

In 2006, and after much debate, the International Astronomical Union came up with a new definition for a planet. And for the first time, the term "dwarf planet" was used.

An image of Pluto taken by the New Horizons probe in 2015 with evidence for potential cryovolcanism marked in blue.

Ice volcanoes on Pluto may still be erupting

By Rebecca Sohn last updated

An area of Pluto that researchers think was formed from the eruption of ice volcanoes is unique on the dwarf planet and in the solar system, a new study suggests.

March is a month of transition, as we change seasons from winter to spring. Here's some strange things to see in the night sky.

March night sky wonders: Strange sights to see every year

By Joe Rao published

Reference A look into the March night sky for some sky objects with unusual solar system planets, stars and constellations.

The surface of Pluto’s icy Sputnik Planum — seen here in a photo captured by NASA’s New Horizons spacecraft during its close flyby of the dwarf planet on July 14, 2015 — is covered with churning ice “cells” that are geologically young and turning over due to convection.

Pluto's bizarre polygons now have a science explanation

By Elizabeth Howell published

The icy process may be present on other worlds.

Artist's impression of NASA's New Horizons spacecraft.

New Horizons: Exploring Pluto and Beyond

By Elizabeth Howell published

New Horizons was the first spacecraft to visit dwarf planet Pluto and Kuiper Belt object Arrokoth. The spacecraft is still actively exploring the solar system.

A new study shows how Pluto's atmosphere is disappearing.

Pluto's atmosphere is starting to disappear, scientists find

By Chelsea Gohd published

Pluto's atmosphere is going through a strange transformation, scientists are finding.

The yellow arrow shows the trajectory of New Horizons over the surface of Pluto.

NASA celebrates New Horizons' historic Pluto flyby in 2015 with awesome new videos

By Tereza Pultarova published

NASA has released new visualisations of the dwarf planet Pluto and its largest moon Charon to commemorate the first-ever up close exploration of the distant worlds.

Using New Horizons' MVIC Pluto's Sputnik Planum comes to life in vibrant colors.

Tantalizing Pluto views suggest active surface but won't be seen again for 161 years

By Meghan Bartels published

For a brief moment in time in July 2018, the solar system aligned to show Earth the fully sunlit disk of Pluto, an arrangement that won't occur again for 161 years.

NASA's New Horizons spacecraft captured this image of the blue haze around the dwarf planet Pluto during its historic flyby in 2015.

Pluto's atmosphere gets its blue haze from icy organic compounds, study suggests

By Charles Q. Choi published

The haze shrouding Pluto might be made up of ice crystals possessing cyanide hearts, a new study finds.