The fastest spacecraft ever built has nearly touched the sun. NASA’s Parker Solar Probe, which launched in 2018, has set two records at once: the closest spacecraft to the sun and the highest speed reached.
On 29 April, the probe made its closest pass yet to the sun, a little more than 10 million kilometres from its surface. During the time of closest approach, it was travelling at about 150 kilometres per second relative to the sun, the fastest any spacecraft has ever moved.
At this rate, it would take about 4.5 minutes to cover the entire circumference of Earth, or around 40 minutes to fly from Earth to the moon. It is about 0.05 per cent of the speed of light.
But the Parker Solar Probe isn’t done yet: the fly-by of the sun on 29 April was only the spacecraft’s eighth pass out of a planned 24 before the end of the mission in late 2025. On each pass, the probe first sails out past Venus to use the planet’s gravity to shape its orbit, pushing the spacecraft closer and closer to the sun.
That proximity will help it swing by at increasing speeds, with a planned top speed of around 200 kilometres per second. At that pace, it will be almost three times faster than the previous record-holders, a pair of spacecraft called the Helios probes that studied the sun in the 1970s.
At its closest, the Parker Solar Probe will be just less than 7 million kilometres from the sun, more than 6 times closer to it than the Helios probes were, which held the record until Parker broke it in 2018.
While the spacecraft is close to the sun, its goals lie beneath the surface – the probe is designed to measure the magnetic fields in the region and trace the flow of energy within the sun. These measurements should help researchers understand how the sun blasts out the energetic particles that make up the solar wind, as well as the mystery of why the outermost layer of the sun is hotter than the inner layers.
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