New Horizons at Pluto
On 14 July 2015 New Horizons flew past Pluto and showed, for the first time up close, its heart-shaped plain and flowing nitrogen ice.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
At 11:49 UT on 14 July 2015, the New Horizons spacecraft passed 12,500 km above Pluto. It was moving at about 50,000 km/h, fast enough to cover the distance from London to Paris (about 340 km) in under half a minute. Launched in January 2006, it had flown some five billion kilometres over nine and a half years for this single day. The probe stayed silent during the flyby so it could spend every moment observing, and when its “all is well” signal reached Earth about 13 hours later, the control room burst into cheers.
The Pluto that came back was not the one scientists had expected. On the heart-shaped plain called Sputnik Planitia, nitrogen ice was slowly flowing like a glacier, and mountains of water ice rose several kilometres high. Craters build up over long ages as space rocks fall, yet this plain had almost none. That told scientists its surface was younger than about ten million years. A world many had pictured as a frozen, unchanging ball of ice turned out to be still changing today.
The encounter nearly went wrong. On 4 July, ten days before the flyby, the spacecraft’s computer was given too many tasks at once, became overloaded and put the probe into safe mode. Contact with Earth was lost for a little over an hour, and science observations only restarted on 7 July. The team carefully rechecked the flyby plan, and the observations on 14 July were carried out as intended.
Sending all the data home took about fifteen months. From five billion kilometres away the signal carried only one to two kilobits per second, so even a single smartphone-sized photo would take hours. New Horizons went on to fly past the Kuiper-belt object Arrokoth on 1 January 2019, and as of April 2026 it was about 64 AU from the Sun. In the orbit view, moving the time to 14 July 2015 replays the probe sweeping past Pluto.
Mission goals
With the Pluto flyby, every one of the nine bodies once called the planets had been visited up close by a spacecraft. Counting from Mariner 2’s pass of Venus in 1962, it took 53 years. What remains are orbiters and landers that stay at a world, and the countless small icy bodies scattered through the Kuiper belt.
Finding that Pluto is still changing raised a new question. Some moons of Jupiter are kept warm inside because the giant planet squeezes and stretches them, but Pluto gets almost none of that. How it keeps a young surface is still not settled. Scientists think a liquid ocean may be hidden beneath its icy shell, and they now ask the same question about other dwarf planets such as Eris.
Pluto’s largest moon, Charon, was also seen in detail for the first time. Its north polar region is stained red, and its surface is cut by canyons hundreds of kilometres long. Pluto and Charon circle a point in the empty space between them, facing each other as they turn, and New Horizons photographed both faces of this unusual pair up close.
Mission chronology and background
After passing Pluto, the spacecraft deliberately flew into Pluto’s shadow. From there, sunlight had to pass through Pluto’s thin air to reach the probe, and measuring how much the light dimmed revealed the atmosphere’s thickness and temperature. The result was a surface pressure of about one pascal, roughly one hundred-thousandth of the air pressure at Earth’s surface.
The final weeks before the flyby were spent looking for danger. At 50,000 km/h even a grain of dust could have harmed the spacecraft, so the team had to find out whether any unknown small moons or rings lay in the way. During the approach in May and June 2015 the cameras searched the surroundings carefully, nothing dangerous turned up, and the probe kept its planned path. Backup routes had been prepared just in case.
Arrokoth, reached on 1 January 2019, was about 43 AU from the Sun and became the most distant object any spacecraft had studied up close. About 36 km long, it looks like a snowman made of two rounded lumps joined together. Because it shows almost no sign of a violent crash, scientists see it as evidence that, when the solar system was forming, small lumps drifted together slowly and stuck gently.
Where to see it — sky and simulator
Pluto shines at about 14th magnitude, roughly 1,500 times fainter than the dimmest star the naked eye can see. A telescope about 30 cm across is needed to show it as a tiny point, and to tell it from the stars one must compare photos taken a few nights apart and look for the dot that has moved. Select Pluto in the sky view to see where it is in Capricornus now and when it rises.
Follow Pluto in the orbit view and move the time to 14 July 2015 to replay New Horizons sweeping past, with Charon circling face to face with Pluto every 6.4 days. In the 3-D interstellar view, switching on the solar-system structure chip draws Pluto inside the Kuiper belt, which stretches from about 30 to 50 AU, and the probe’s marker beyond it, heading toward Sagittarius.
See this for yourself — replay the moment in the orbit view
FAQ
How close did it pass?
It passed 12,500 km above Pluto at about 50,000 km/h on 14 July 2015.
Why did the data take fifteen months to arrive?
From five billion kilometres away it could send only one to two kilobits per second, so even one photo took hours.
What is Pluto’s heart?
It is Sputnik Planitia, a basin about 1,000 km across where nitrogen ice slowly flows; it has almost no craters, so its surface is young.
Where is the probe now?
As of April 2026 it was about 64 AU from the Sun toward Sagittarius, still studying the outer edge of the solar system.
Related
- New Horizons launch — to Pluto
- Voyager 2 at Neptune
- Voyager 1 enters interstellar space
- Pluto — object index
- New Horizons — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.