Launched in 2018, NASA’s Parker Solar Probe has been making groundbreaking strides in solar research. In its mission to study the sun up close, the spacecraft has already achieved a monumental feat by flying through the sun’s corona—the outermost layer of its atmosphere, visible during solar eclipses.

The next major milestone is set for this Tuesday, when Parker will make its closest approach yet, coming within a record 3.8 million miles (6 million kilometers) of the sun’s surface. According to NASA scientist Joe Westlake, this is equivalent to being at the 4-yard line if the sun and Earth were positioned at opposite ends of a football field.

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Due to communication limitations during the flyby, mission controllers won’t know the spacecraft’s status until several days afterward. Designed for extreme conditions, Parker will travel at an unprecedented speed of 430,000 mph (690,000 kph), making it the fastest spacecraft ever constructed. Its advanced heat shield can endure temperatures as high as 2,500°F (1,371°C).

Parker will maintain its proximity to the sun until at least September, providing scientists with valuable insights into the solar corona, which is mysteriously hundreds of times hotter than the sun’s surface. Researchers also hope to uncover the mechanisms behind the solar wind—a continuous stream of charged particles that can occasionally disrupt Earth’s communications and power systems.

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Currently, the sun is in the peak phase of its 11-year cycle, a period marked by heightened solar activity and vivid auroras appearing in unexpected regions.

Describing the sun’s dual nature, Westlake remarked, “It is our closest, friendliest neighbor, but at times, it shows a fiery temperament.”