How hot is the Sun, the corona? How NASA ‘ s Parker, solar probe will keep its cool

An image of the sun taken in 1997 shows the temperature of the corona of the sun (in lighter colors) in comparison with the cooler temperatures of the surface of the sun (dark colors).


If you think that a sunny day here on Earth gets toasty, imagine how much hotter it would be if you fly through the upper layers of the solar atmosphere.

The answer is a whole lot warmer, in the millions of degrees whether measured in Fahrenheit or Celsius, according to NASA. And that incredibly warm upper layers of the atmosphere is exactly what a new NASA spacecraft will head after the launch later this week.

The mission, called the Parker Solar Probe, is designed to crack mysteries about the sun and the stars. To beat the heat, it is armed with a secret weapon that most of the instruments on a balmy 85 degrees Fahrenheit (30 degrees Celsius): a high-tech, lightweight, thermal shield. [The Largest Missions to the Sun]

But even the hot side of the heat shield is not really to get millions of degrees itself, despite flying through the hottest part of the sun.

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“Think of putting your oven on and set it to 400 degrees, and you can get your hand in your oven and you will not be burned, unless you actually touch a surface,” Parker Solar Probe project scientist Nicola Fox, a solar researcher at the Johns Hopkins University, said on July 20, during a NASA press conference about the upcoming mission. “It is really the same.”

The more bearable temperature thanks to the thin, irregular structure of the corona of the sun itself, that is the atmosphere that can not be seen without blocking the photosphere — the incredibly clear and low that we think of as the surface of the sun.

That means, for a preset time, the heat shield does not hit all that a lot of superhot particles of the plasma, which makes the corona — which means that, although each individual collision brings a reasonable amount of heat to the shield of the surface area, the total increase in the shield of the temperature bearable.

“The corona is very rarefied plasma; it is not a hugely populated area,” Fox said. “So, if you think about the amount of particles actually striking the heat shield and the deposition of that heat in, the whole is heated to 2,500 degrees Fahrenheit [1,370 degrees C].”

That is a much more manageable temperature of the heat shield to resist — the equivalent of putting your hands in the oven without touching a surface. “If I would just say, ‘Don’t touch the oven surface,’ don’t touch the 3-million-degree plasma,” Fox said. And the Parker Solar Probe will respond to this advice, only to fly through the corona of the sun without hitting dense concentrations of plasma.

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