The Parker Solar Probe is set to make a historic pass by the sun on Tuesday, marking the closest approach to a star ever achieved by humankind. It will come within a mere 3.8 million miles (6.1 million kilometers) of the sun's surface, traveling at an astonishing speed of 430,000 miles per hour (692,000 kilometers per hour). This velocity is so swift that it could transport one from Washington, D.C., to Tokyo in less than a minute, as stated by NASA. This record-breaking speed has earned the probe the title of the fastest man-made object in history, a fact revealed by the agency during a NASA Science Live presentation on December 16th on YouTube.

The mission, which began with its launch on August 12, 2018, has been leading up to this monumental event. The probe was named after Dr. Eugene Parker, a pioneering astrophysicist in the field of heliophysics, who was the first living person to have a spacecraft named in his honor. Sadly, Dr. Parker passed away in March 2022 at the age of 94, but he lived to see the probe's potential to unravel long-standing mysteries about the sun, more than six decades after the mission's initial conception.

In December 2021, the probe made history by being the first to "touch the sun" by flying through the sun's corona, or upper atmosphere, to sample particles and the star's magnetic fields. Over the course of its seven-year mission, the Parker Solar Probe has been gathering data to shed light on some of the sun's most perplexing enigmas. Scientists have long been intrigued by the generation of solar wind, a continuous stream of particles emitted by the sun, and the reason behind the sun's corona being significantly hotter than its surface. Additionally, there is a keen interest in understanding the structure of coronal mass ejections, which are large plasma clouds of ionized gas and magnetic fields that erupt from the sun's outer atmosphere. When these ejections are directed towards Earth, they can induce geomagnetic storms, significant disruptions to the planet's magnetic field, affecting satellites and terrestrial power and communication infrastructures.

Now, as the Parker Solar Probe prepares for its closest and final flybys, it may provide the answers to these enduring questions and potentially uncover new mysteries by venturing into unexplored regions of the solar sphere. "The Parker Solar Probe is transforming the field of heliophysics," remarked Helene Winters, the project manager of the Parker Solar Probe from Johns Hopkins University's Applied Physics Laboratory. "After enduring the heat and dust of the inner solar system, and withstanding blasts of solar energy and radiation unseen by any spacecraft, the Parker Solar Probe continues to excel."

Scheduled for around 6:53 a.m. ET on Christmas Eve, Parker's flyby will be the first of the spacecraft's final three closest approaches, with subsequent encounters expected on March 22 and June 19. The proximity is so close that if the distance between Earth and the sun were to be likened to the length of an American football field, the spacecraft would be approximately 4 yards from the end zone, according to NASA. At this near distance, the probe will be able to fly through plumes of plasma and even within a solar eruption if one occurs.

The spacecraft was designed to endure the extremes of the sun and has previously flown through coronal mass ejections without any damage, as stated by Parker Solar Probe project scientist Nour Rawafi. It is equipped with a carbon foam shield that measures 4.5 inches (11.4 centimeters) thick and 8 feet (2.4 meters) wide. Before launch, this shield was tested and proven capable of withstanding temperatures nearing 2,500 degrees Fahrenheit (nearly 1,400 degrees Celsius). On Christmas Eve, the shield may face temperatures up to 1,800 F (980 degrees C), while the spacecraft's interior will maintain a comfortable room temperature to ensure the electronics systems and scientific instruments function as intended. A unique cooling system, designed by the Applied Physics Laboratory, circulates water through the craft's solar arrays to maintain a steady temperature of 320 F (160 C), even during close encounters with the sun.

The spacecraft will conduct its flyby autonomously, as mission control will be out of contact with the probe due to its proximity to the sun. After the closest approach, around midnight between Thursday and Friday, Parker will transmit a signal known as a beacon tone back to mission control to confirm the success of the flyby, as explained by Rawafi. This beacon tone is a minimal data relay that indicates the overall status of the spacecraft. The extensive dataset and images collected during the flyby will not be available to mission control until Parker moves away from the sun in its orbit, which is expected to happen about three weeks later in mid-January, according to Rawafi.

Just over a year after the Parker Solar Probe's launch, the sun entered a new solar cycle. As Parker makes its closest approach, the sun is currently experiencing solar maximum, indicating the mission has had the opportunity to observe most of a solar cycle and the transitions between its peaks and troughs. In October, scientists from NASA, the National Oceanic and Atmospheric Administration, and the international Solar Cycle Prediction Panel announced that the sun had reached solar maximum, the pinnacle of activity within its 11-year cycle. At the peak of the solar cycle, the sun's magnetic poles reverse, causing the sun to shift from a calm to an active state. Solar activity is tracked by counting the number of sunspots appearing on the sun's surface. The sun is anticipated to remain active for the next year or so.

The sun's increasing activity was evident this year during two significant aurora displays on Earth in May and October, when coronal mass ejections directed at our planet resulted in solar storms. These solar storms are also responsible for the auroras that dance around Earth's poles, known as the northern lights or aurora borealis, and the southern lights or aurora australis. When the energized particles from coronal mass ejections reach Earth's magnetic field, they interact with atmospheric gases to create a spectrum of colored lights in the sky.

"Both of those storms made auroras visible down to the very bottom of the United States," said Dr. C. Alex Young, associate director for science in the Heliophysics Science Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. "However, the May storm was particularly strong. In fact, we believe it could be a 100- to possibly 500-year event, causing auroras very close to the equator, which is extremely rare. It was a global event that millions, and hopefully billions, of people were able to witness, and it may not occur again."

The data collected by the Parker Solar Probe could enable scientists to better comprehend solar storms and even predict them, according to Young. "The sun is the only star we can see in detail, but we can actually go to and measure it directly," Young said. "It's a laboratory in our solar system that allows us to learn about all the other stars in the universe and how all those stars interact with the billions and billions of other planets that may or may not be like our own planets in our solar system."

With this in mind, Rawafi expressed his hope that the sun will put on a spectacular display during the probe's close approaches, providing scientists with insights into the sun's activity. "Sun, please do your best," Rawafi said. "Give us the strongest event you can do, and the Parker Solar Probe can handle it."