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[00:00.45] The Parker Solar Probe, the fastest object ever made by human hands, surfs the solar winds at more than 630,000 kilometers per hour.

[00:11.61] That’s more than 500 times the speed of sound on Earth. Its mission?

[00:17.18] To touch the Sun— and, ideally, to avoid melting in the process.

[00:23.03] It achieved this goal in 2021, when the probe flew by Venus and skimmed through the corona, the Sun’s outermost atmosphere.

[00:33.92] Since then, it's carved closer and closer paths, revealing extraordinary details about our star in the process.

[00:42.95] On its closest approach, it’s projected to cross within 8.8 solar radii— that’s less than 4.5 sun lengths away from the solar surface.

[00:54.37] And it will endure temperatures of 1,500 degrees Celsius.

[01:00.48] But there’s a limit to just how close Parker can get.

[01:04.20] And there are questions scientists can't answer without probing even deeper into the solar atmosphere.

[01:11.90] Among these mysteries is the astonishing fact that the solar surface is actually much cooler than the outer corona.

[01:20.14] Above the solar surface is a thin 100 kilometer layer known as the transition zone, where temperatures dip from a scorching 500,000°C to a relatively cool 8,000 degrees.

[01:35.54] While physicists have theories on how the transition zone forms, we won't know for sure until we can make closer observations.

[01:44.31] Further, some scientists predict that if a spacecraft could fly within about 3 solar radii from the Sun’s surface and fire its rockets at just the right time, it could use the Sun’s gravity to slingshot itself into the outer solar system.

[02:02.64] This daring flight path, called the Oberth maneuver, could propel a spacecraft past Pluto in just three years, a trip that currently takes around a decade.

[02:15.12] But probing deeper into the corona— without melting, exploding, or falling directly into the Sun— is a monumental engineering challenge.

[02:24.42] The first challenge is directing the probe's path.

[02:27.87] A probe falling directly towards the Sun would likely pick up so much speed in its descent that it would either crash or be flung in the opposite direction.

[02:38.23] To avoid this, the Parker Space Probe made a series of complicated orbital maneuvers around Venus.

[02:46.20] Using the planet’s gravity as a brake, it could readjust its orbit and get incrementally closer.

[02:52.84] But these current orbital tricks can only get us so far.

[02:57.62] As for the scorching heat, the Parker Probe used a strategy that is not unlike sitting under a beach umbrella.

[03:06.12] Its instrumentation is packed behind a heat shield just 4.5 inches thick.

[03:12.23] One side is made of highly reflective white ceramic that scatters much of the incoming sunlight.

[03:19.14] The other side consists of a carbon foam sandwiched between two layers of carbon, further reinforced with carbon fiber.

[03:28.70] The foam is around 97% air, so it acts as an insulator, not allowing much heat to flow through.

[03:36.67] The outer carbon panel is very dark and can withstand high temperatures, so it efficiently absorbs any remaining heat and radiates it back out to space.

[03:47.82] A sensor system constantly adjusts this shield to ensure the craft’s instruments remain in its shadow.

[03:55.53] But Parker’s heat shield can only get so close.

[03:59.51] To get even closer, one possibility would be to ditch the heat-absorbing carbon materials entirely and double down on deflection.

[04:09.60] Researchers at NASA’s Innovative Advanced Concepts program have developed a novel ultra-reflective coating called Solar White that’s predicted to reflect 99.9% of the Sun’s energy.

[04:24.48] They plan to use Solar White to coat an outer curved umbrella-like shield.

[04:30.32] Then, a second conical shield made from a silvered reflective material would shunt away any remaining radiation that escapes through.

[04:40.15] With both novel shields, scientists believe they could surf a probe as close as 2 solar radii from the surface.

[04:48.65] But we won’t know for sure until these materials are further tested.

[04:53.17] At these close distances, we might unlock the mystery of the transition zone.

[04:58.21] We may learn how to better predict solar behaviors like flares and geomagnetic storms, which puts satellites and our communication systems on Earth at risk.

[05:09.37] And we’d get an unprecedented look at our star, and perhaps one day, with the Sun’s assistance, at our most distant neighbors.