# Why didn't the Parker probe melt when "touching" the Sun? This is how your heat shield works

On December 15, the Parker probe became the first spacecraft to "touch" the Sun, but instead of ending up melted before the high temperatures of the largest source of electromagnetic radiation in our solar system, it took particle samples, analyzed magnetic fields and continued his journey .

But how is it possible that a device sent from Earth is capable of operating in such extreme conditions? The keys are in the low density of the particles in the Sun's atmosphere and in an advanced thermal protection system.

The Sun's atmosphere is not what it seems

The temperature of the Sun's atmosphere , where the Parker probe made its most recent walk, can exceed a million degrees Celsius . This represents values ​​much higher than those of the solar surface, estimated at about 5,500 ° C, which would be a threat to any device.

However, contrary to what our intuition tells us, heat is not the same as temperature. As NASA explains, " high temperatures do not always translate into heating of another object ." That is, a temperature can be millions of degrees and not provide significantly high heat.

While temperature is a measure of the kinetic energy of the particles (they move and collide with each other), heat is the thermal energy transferred between two different systems. Particles can move quickly (high temperature), but if there are too few of them, they do not transfer much energy (low heat) .

What happens in the Sun's atmosphere, also called the corona, is that the particles that make it up have a particularly low density, so the amount of energy transferred by the space probe is not so high. This means that the heat shield does not have to cope with a temperature of more than a million degrees but of about 1,400 ºC.

A shield to protect the probe from the Sun

The Parker probe thermal protection system

Thousands of degrees Celsius is hot anyway. Therefore, the Parker probe has a thermal protection system. Its 2.4 meters in diameter and approximately 115 mm thick allow the interior of the ship to remain at about 30 ºC to protect all the electronic components.

The thermal protection system, like the probe, has been designed by the Johns Hopkins Applied Physics Laboratory. The front and back faces of it are made of two layers of carbon , a material whose properties are adequate to resist high temperatures.

In addition, between each layer of carbon there is carbon foam. The entire protection system has a glossy white aluminum oxide- based coating designed to reflect as much heat as possible and, as a whole, withstand up to 1,650 ºC in an environment as hostile as the solar atmosphere.

The Parker probe, which was launched into space on August 12, 2018, has already broken several records. It is the fastest human-created object and the first to reach the Sun. In its seven years of life, it will approach the main star of our solar system a total of 21 times.