Parker Solar Probe at closest approach
On 24 December 2024 the Parker Solar Probe came within about 6.1 million km of the Sun's surface. It was the closest any human-made object had come to the Sun, and it was moving at about 690,000 km/h.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
On 24 December 2024 NASA's Parker Solar Probe came within about 6.1 million km of the Sun's surface. It was the closest any human-made object had ever come to the Sun. At that moment it was travelling at about 690,000 km/h, or about 191 km every second. At that speed it could cover the distance from London to Paris (about 340 km) in less than two seconds, which also made it the fastest object people have ever built.
This close pass was not luck; it was planned for years. After its launch in August 2018, Parker flew past Venus seven times. Each Venus flyby slowed it down, letting it fall a little deeper toward the Sun. The final Venus flyby, on 6 November 2024, set up the closest approach on Christmas Eve. Now Parker goes around the Sun every 88 days and comes back to the same closest distance each time.
What protected the spacecraft was a carbon-composite heat shield 11.4 cm thick. The side of the shield facing the Sun heats up to about 1,370 °C, while the instruments in its shadow stay at around 29 °C. During the closest approach, contact with Earth was cut off. On 26 December a signal saying all was well reached Earth and confirmed success, and detailed data began arriving on 1 January 2025.
Parker flies right through the inner part of the corona, the Sun's outer atmosphere, gathering data. Its goals are to find out where and how the solar wind, a stream of electrically charged particles blowing out from the Sun, speeds up, and why the corona is so hot. The orbit view reproduces Parker's orbit tightening toward the Sun with each Venus flyby, and that final closest approach.
Mission goals
Why the corona is so hot has been a puzzle since the 1940s. The Sun's surface is about 5,500 °C, yet the corona above it is more than a million degrees. It is as strange as the air getting hotter the farther you move from a stove. Parker is a spacecraft that goes right into that region to measure magnetic fields and particles. Scientists hope its data will reveal what heats the corona.
This research also matters for everyday life. The solar wind and huge bursts of material thrown out by the Sun can affect satellites, power grids and communications. Together these effects are called space weather. Measurements taken close to the Sun help forecast when such space weather will reach Earth.
During its first close passes in 2018, Parker discovered switchbacks: sudden flips in the direction of the magnetic field within the solar wind. Scientists think these may start close to the Sun's surface and may be linked to how the solar wind speeds up. The exact cause, however, is still being studied. The closer Parker goes to the Sun, the more clues it gathers about this puzzle.
Mission chronology and background
The spacecraft is named after the American physicist Eugene Parker. In 1958 he proposed the theory of the solar wind, the idea that particles stream out from the Sun all the time. At first many scientists did not believe him, but in 1962 the Venus probe Mariner 2 measured the solar wind and showed that he was right. Parker watched the 2018 launch in person and died in 2022.
Before Parker, the record for the closest approach to the Sun was set by Helios 2 in 1976, at about 43 million km. Parker went about seven times closer than that. On 28 April 2021 it also became the first spacecraft to enter the Sun's corona, by crossing the Alfvén surface, the boundary inside which the Sun's influence dominates.
The European Space Agency's Solar Orbiter, launched in 2020, is also studying the Sun. Solar Orbiter takes pictures of the Sun from farther away, while Parker measures particles and magnetic fields up close. Looking at data from both spacecraft together helps scientists understand the corona during the Sun's most active years from inside and outside at once.
Other milestones of this mission
Where to see it — sky and simulator
Parker cannot be seen with bare eyes or with any telescope. The moment of closest approach is not something to watch in the sky; it is a time when the spacecraft is busy collecting data. The data are sent back to Earth over several weeks after each pass. Parker made further passes at the same distance on 22 March and 19 June 2025.
The orbit view reproduces, in time order, how the orbit narrowed through seven Venus flybys after the 2018 launch, and the replay slows at the closest approach of 24 December 2024. When the view follows the spacecraft, its path seems almost to touch the Sun's disk, but in reality it stays about nine times the Sun's radius away from the surface.
The Sun must never be looked at with bare eyes, without a proper filter. Selecting the Sun in the sky view shows how high it is above your location right now and the path it takes across the sky during the day. The brightness of the daytime sky is also reproduced to match the Sun's real height. You can also see how the colour and brightness of the sky change as the Sun's height changes.
See this for yourself — replay the moment in the orbit view
FAQ
How close and how fast did it go?
It passed about 6.1 million km from the Sun's surface at about 690,000 km/h. Both are records for a human-made object.
Why did it not melt?
An 11.4 cm carbon-composite heat shield faces the Sun, and the body of the spacecraft hides in its shadow. The front of the shield reaches about 1,370 °C, while the instruments behind it stay at about 29 °C.
Was this the last close pass?
No. It goes around the Sun every 88 days and returns to the same distance each time, including passes on 22 March and 19 June 2025.
What is it trying to learn?
Why the corona is much hotter than the Sun's surface, and where the solar wind speeds up. The data also help forecast space weather at Earth.
Related
- Parker Solar Probe launch
- Mariner 2 — measuring the solar wind
- BepiColombo launch — to Mercury
- Parker Solar Probe — object index
- The Sun — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.