Grazing the Sun

The Parker Solar Probe launches today in what is an ambitious scientific endeavour, flying in to graze the Sun in an elliptical orbit comparable to that of a comet.

Falling seems easy. For us, it’s hard to avoid and we have to be careful climbing ladders, trees, etc, but falling into the Sun is hard. Seems counterintuitive but remember Earth orbits the Sun at 108,000 km/hr. That is crazy fast, but we don’t notice our speed in the same way someone sitting in the back seat of a car racing down the highway, lost in the glare of their smartphone, might not realize they’ve pulled out of the parking lot.

Imagine falling into the Sun like throwing a ball from a car on the highway. If you aim for a highway sign, you’ll miss. Why? Because the ball has your momentum. Your aim might be true and perfectly good if the car was sitting still, but as you’re in motion you’ll miss and the ball will sail past the sign. In the same way, the Parker Solar Probe needs to lose a lot of the orbital momentum it gets from Earth. To do this, scientists have devised a neat trick. They’re going to loop the probe around both the Sun and Venus. With each pass of Venus, it’ll lose a little more momentum and fall deeper in toward the Sun. This process will take several years to complete.

The Sun is massive. It’s far bigger than most people realize. We live on Earth, which is massive. We look at other planets like Saturn, Jupiter, Neptune and Uranus which all dwarf Earth, but the Sun is the monster powering this system, containing 99.8% of ALL the mass in our solar system. Yep, the planets are a rounding error in the formation of the Sun.

At its closest approach, the Sun will look something like this…

Image credit: Spacecraft: ESA/ATG medialab; Sun: NASA/SDO/P. Testa (CfA)

The Parker Solar Probe is going to pass within roughly 4 million miles of the Sun, whereas Earth orbits at an average of 97 million miles. Falling in that close to such a massive body, the probe is going to pick up some tremendous speed, traveling at upwards of 700,000 kilometers an hour (or 430,000 mph relative to the sun)! That’s the equivalent of traveling from Philadelphia to Washington DC in a second, or New York to LA in 20 seconds!

Temperatures on the probe are expected to hit around 1370°C/2500°F in the sunlight and 30°C/85°F in the shade. While in sunlight, the temperature will be hot enough to melt aluminum, copper, brass, cast iron, nickel, etc and is right on the verge of melting silicon itself, making the design particularly tricky. It’s interesting to note that the probe will fly through a portion of the corona that reaches well over a million degrees, but as it is rarified (extremely thin) the temperature of the probe won’t exceed 2500F.

As with all scientific experiments, decades of planning has gone into the mission. We are yet again on the verge of unraveling more of the cosmic mystery surrounding our origins and how the universe works as we take our first close observations of a star.

The Parker Solar Probe is named after the 91 year old Eugene Parker who first proposed the concept of solar winds, and he’ll be watching the launch live!

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