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Why it matters: The Parker Solar Probe is on an ambitious mission to study the origins of the solar wind – the constant stream of charged particles flowing outward from the sun. Despite over half a century of scientific investigation since its discovery in the 1960s, the phenomenon’s precise source within the corona remains unknown.
We’re just days away from the Parker Solar Probe making its closest approach yet to the sun. The little spacecraft will barrel through the sun’s outer atmosphere on Christmas Eve, passing within just 3.8 million miles of the surface below. 
That may sound like a significant distance, but for a red-hot celestial ball with a diameter of 865,370 miles, this is the closest we’ll have ever been. In fact, the probe will go right through the solar corona, which is the super-heated atmosphere extending millions of miles from the sun’s visible surface. Because of this, the probe will endure extremes few things on Earth do, with NASA estimating its heat shield will experience temperatures exceeding 2,500°F.
Nicky Fox, who formerly served as the probe’s project scientist before becoming NASA’s Chief Scientist, explained to Ars Technica that the core objective is to pinpoint the birthplace of solar winds.
To unlock that mystery, there’s no substitute for actually venturing into the sun’s outer atmosphere to take measurements. But as Fox noted, that’s an immense engineering challenge because the sun is, quite literally, on fire.
The probe had to be meticulously designed to endure the extreme heat and radiation of the corona, only to rapidly cycle back into the cold vacuum of space on its elliptical orbits around the sun. Fox elaborated that careful material selection was crucial, requiring lightweight yet durable components that could withstand drastic temperature shifts without becoming brittle or exhibiting changing properties.
Exotic metal alloys like titanium-zirconium-molybdenum with melting points over 4,200°F were used for sensors exposed to the sun’s intensity. Even the wiring, which was built using niobium, needed special sapphire crystal insulation to prevent it from melting. It took years of planning and technological breakthroughs to build a spacecraft capable enough.
Appropriately, the probe honors the physicist Eugene Parker, who originally predicted the existence of the solar wind back in the 1950s. This theory initially met with widespread skepticism, that is until observations from 1962’s Mariner 2 spacecraft confirmed it.
Now over six years into its mission, the Parker Solar Probe is gearing up to provide our most extreme glimpse yet into the sun’s atmosphere and the origins of this fundamental solar phenomenon.
Despite incredible achievements like becoming the fastest human-made object at over 430,000 mph, the probe hasn’t gotten much mainstream attention lately. But that may change after this record-close encounter and the new scientific insights it might bring.
Image credit: NASA
