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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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.

The snowcapped mountains of Pluto's Pigafetta Montes and Elcano Montes and the Alps on Earth are seen side by side in this view.

The mountains on Pluto have super weird methane ice snowcaps

By Charles Q. Choi published

Mountains on Pluto have snowcaps that may have formed from the top down as opposed to the bottom up, the reverse of how snow caps form on Earth, a new study finds.

An artist's depiction of the Enceladus Orbilander mission concept.

Where to next in the outer solar system? Scientists have big ideas to explore icy moons and more.

By Meghan Bartels published

If you had a few billion dollars and some of the most talented space scientists and engineers in the world, where would you go?

This image from New Horizons shows the dwarf planet Pluto in stunning detail.

Glaciers on Pluto might 'grow' with the seasons

By Chelsea Gohd published

Methane and nitrogen glaciers on Pluto expand and "grow" in response to temperature changes on the dwarf planet, new research suggests.

Pluto’s haze layer displays a blue color in this image obtained by the New Horizons spacecraft's Ralph/Multispectral Visible Imaging Camera (MVIC).

Pluto flyby photos: New Horizons mission leader Alan Stern reveals 10 of his favorite epic views

By Mike Wall last updated

New Horizons' epic Pluto encounter took place five years ago. Celebrate the anniversary with a look at some of the probe's most dramatic and intriguing photos.

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

Pluto revealed: 5 years ago, NASA's New Horizons gave us our first close look at this distant world

By Mike Wall last updated

Five years ago today, we started to appreciate just how remarkable Pluto really is.

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

Surprise! Pluto may have had an underground ocean from the very beginning

By Charles Q. Choi published

Though Pluto is now famously frigid, it may have started off as a hot world that formed rapidly and violently, a new study finds.

Pluto’s haze layer displays a blue color in this image obtained by the New Horizons spacecraft's Ralph/Multispectral Visible Imaging Camera. Image released Oct. 8, 2015.

Pluto's wispy atmosphere may be surprisingly robust

By Mike Wall published

Pluto's thin, blue-tinged air may not collapse when the dwarf planet is far from the sun.

The Dark Energy Camera is mounted on the Victor Blanco telescope, pictured here with other telescopes at the Cerro Tololo Inter-American Observatory in Chile.

'Minor planet' bonanza: 139 new objects discovered beyond Neptune

By Mike Wall published

The list of Pluto's neighbors just got considerably longer, potentially boosting scientists' odds of finding the putative Planet Nine.

An undated photograph of Elizabeth Williams.

Meet the unknown female mathematician whose calculations helped discover Pluto

By Meghan Bartels published

Pluto's discovery wouldn't have been possible, astronomers have realized, without the calculations of a mathematician whom history has forgotten.

The left lobe of Pluto's heart-shaped feature is a 600-mile-wide (1,000 kilometers) ice plain known as Sputnik Planitia.

Pluto's famous heart powers icy winds on the dwarf planet

By Mike Wall published

Pluto's heart-shaped feature, which NASA's New Horizons spacecraft discovered during its epic July 2015 flyby of Pluto, drives atmospheric circulation on the dwarf planet, a new study suggests.

NASA's New Horizons spacecraft discovered layers of haze on the dwarf planet Pluto during its 2015 flyby.

Pluto and Titan are surprisingly hazy, but scientists are fuzzy on exactly why

By Meghan Bartels published

NASA's New Horizons mission turned Pluto from a fuzzy blob into a detailed, geophysically complex world. But it's still a little fuzzy, as it turns out.

The most detailed image of Arrokoth, captured just minutes before New Horizons made its closest approach on Jan. 1, 2019.

One Year Ago, NASA's New Horizons Made the Most Distant Flyby in Space History

By Nola Taylor Tillman published

A year after New Horizons buzzed its second target, Arrokoth, a wealth of science has been revealed.

Artist's illustration of a black hole.

The Decade in Astronomy: These Space Discoveries Shaped the 2010s

By Sarah Wells published

As the 2010s come to a close, it's time to revisit how some of the biggest space science stories shaped the decade.

NASA's New Horizons spacecraft flew by the distant Kuiper Belt object Ultima Thule (2014 MU69) on Jan. 1, 2019. The object, the most distant ever visited by a spacecraft, is now called Arrokoth.

Meet Arrokoth: Ultima Thule, the Most Distant Object Ever Explored, Has a New Name

By Mike Wall published

Hopefully you weren't too attached to "2014 MU69," because the most distant object ever explored has a new name.

NASA Administrator Jim Bridenstine spoke last month at the International Astronautical Congress, where he said that Pluto ought to be considered a planet.

NASA Chief Keeps Saying 'Pluto Is a Planet' Because It's a Complex, Amazing World

By Elizabeth Howell published

The long-standing debate over Pluto's planethood recently got a public boost from NASA Administrator Jim Bridenstine, who said the world should definitely be a planet.

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

NASA Eyes a Possible Return to Pluto, with a Longer Stay

By Mike Wall published

NASA is thinking about going back to Pluto, this time to stay for a while.

new horizons spacecraft

Long After Historic Flybys, NASA's New Horizons Is Still Pioneering Science in the Kuiper Belt

By Meghan Bartels published

New Horizons made an epic flyby of a Kuiper Belt object to ring in the New Year — but scientists need brand-new observations to truly understand that data.

New Horizons' photo of Pluto showing the heart-shaped area now informally named Tombaugh Region.

Pluto Still Deserves to Be a Planet, NASA Chief Says

By Passant Rabie published

Pluto lost its "official" planet status over a decade ago, but fans of the solar system's underdog are still rooting for it. And NASA Administrator Jim Bridenstine is one of them.

NASA's New Horizons spacecraft captured this view of Pluto's nitrogen-ice plain Sputnik Planitia during the probe's flyby of the dwarf planet in July 2015.

On Icy Pluto, Volcanoes May Spout Liquid Water

By Charles Q. Choi published