NASA's Parker Solar Probe is about to make its closest approach to the sun.The spacecraft will fly within 3.8 million miles of the solar surface.The spacecraft is collecting essential data that can help inform forecasting models on Earth.The fastest human-made object is hurtling toward the sun at this very moment, approaching speeds of 430,000 mph and on December 24, it's scheduled to make history.NASA's Parker Solar Probe launched in 2018 and has completed 21 close flybys around the sun. However, its mission on Christmas Eve will be unlike any other.At 6:53 a.m. ET, the spacecraft is set to fly the closest to the sun of any human-made object. The mission will take it closer than any previously scheduled or planned future approaches.If all goes to plan, the uncrewed spacecraft will come within 3.8 million miles of the solar surface.NASA anticipates the probe will experience temperatures of 1,800 degrees Fahrenheit, which shouldn't be an issue since the spacecraft's protective heat shield is designed to withstand temperatures over 2,500 degrees Fahrenheit.Yes, 3.8 million miles is far by Earth's standards, but it's ridiculously close when you're out in deep space.It's like if you put the Earth and sun at opposite ends of an American football field: "Parker Solar Probe is on the 4-yard line approaching the sun," Joe Westlake, Director of NASA's Science Mission Directorate's Heliophysics Division, told 6abc Philadelphia."It is getting so close that we're actually in the sun's upper atmosphere. We're actually touching the sun with humanity's first mission to a star," Westlake added.The moment NASA has been waiting forThe Christmas Eve flyby is the moment the mission has been building up to for years."This close approach is only possible because of the mission's orbital design," a NASA spokesperson told Business Insider via email."The spacecraft had to shed a lot of orbital energy to get this close to the sun, so that's why it took several years," the spokesperson added.Over the years the Parker Solar Probe, about the size of a small car, has made increasingly close flybys.For example, in September 2020, it flew within 8.4 million miles of the solar surface. By September 2023, it reached within 4.5 million miles.When the spacecraft makes these close approaches, it cuts communication with Earth and flies autonomously, guiding itself through the sun's harsh upper atmosphere until it's far enough away to reestablish coms.NASA last heard from Parker Solar Probe on December 22 and expects to hear from it again around midnight between Thursday and Friday, Nour Rawafi, Parker Solar Probe project scientist at Johns Hopkins Applied Physics Lab, said during a recent NASA livestream.While flying so close to the sun doesn't hold any promise of discovering alien life there or paving the way for future crewed missions to walk on the solar surface, the Parker Solar Probe's mission is, arguably, more important.Here's what you need to know about this historic mission and how it could help humanity solve some of the world's biggest questions.Parker Solar Probe is helping us answer the big questionsIt may appear calm and quiet from far away, but the sun is a turbulent sphere of activity. It's got solar flares and massive eruptions that fire fast-moving, charged particles deep into our solar system."Without that activity, we would not exist. That activity is really necessary for life to kick off," Rawafi said during NASA's livestream.So, on a grand scale, understanding how our sun works can help us better understand how life originated on Earth and where it might exist elsewhere in the universe.Also, by studying our own star up close, we can learn how other stars in the universe interact "with the billions and billions of other planets that may or may not be like our own planets," Alex Young, associate director for science communication in NASA's Heliophysics Science Division, said during the livestream.Wishing for the biggest explosion everRawafi said the best gift the sun could give scientists during Parker Solar Probe's coming approach is "one of the strongest explosions ever."The sun is currently at asolar maximum a period of peak solar magnetic activity lasting one to two years and causing powerful flares, eruptions, and ejections.Sometimes, the charged particles from these eruptions reach Earth. When that happens, it candisrupt satellites, mess with GPS, and subsequently ground flights. It can also expose astronauts to high levels of space radiation.As we continue to launch more satellites and people into space, these solar events are a growing threat. Yet, scientists don't have a highly accurate forecasting model for warning satellite operators and astronauts far in advance.That's why Rawafi wants a big explosion: The probe would be in a perfect position to study the event mere moments after it occurs, offering scientists swaths of data that could help inform and improve forecasting models.Parker Solar Probe has already collected so much data during its years of operation that it will take decades to study it all, Rawafi said at the American Geophysical Union annual meeting in early December.According to NASA, the spacecraft is scheduled to complete 24 orbits around the sun, with its last two planned for 2025.