For the first time, scientists have created a detailed 2D map of the Sun’s outermost atmosphere. The feat was accomplished using data from NASA’s Parker Solar Probe, which has been moving in and out of the sun’s atmosphere, known as the corona, since 2021.
Parker is the first spacecraft ever to fly so close to a star. This ability is largely due to its exceptional heat shield, which can withstand temperatures in excess of 2,500 degrees Fahrenheit (1,370 degrees Celsius). The sun’s corona is much hotter, about 1 million to 3 million F (555,000 C), but it’s so diffuse that objects moving quickly through it don’t encounter many superheated particles. This allows Parker to briefly graze the outer border of the corona.
Once across this boundary, solar particles become caught up in the 1.6 million mph (1.6 million km/h) stream of solar wind that constantly flows from our star, known as the Alfvén surface. This invisible boundary is the point of no return for solar particles, and its exact shape and nature remain largely a mystery to this day.
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The new map, created using data from Parker’s Solar Wind Electron Alpha and Proton Instrument, defines the shape of Alfvén’s surface in more detail than ever before. Parker’s map, using data from the past seven years, proves that Alfvén’s surface regularly changes its shape and extent depending on the degree of solar activity. (The Sun goes through an approximately 11-year cycle of activity, and during solar maximum (its peak period), powerful solar flares and space weather occur more frequently.)
The new map reveals that, as in recent years, Alfvén’s surface is becoming “sharper” and more turbulent as the sun becomes more active. This is important for understanding exactly where the outer edge of the Sun’s atmosphere is and how the solar wind behaves in relation to it. But it could also help protect the technology scientists use on Earth.
Systems such as GPS, communication radios, and power grids are susceptible to disruption from powerful solar flares. Being able to predict when such flares will occur or their strength could help those operating these systems prepare for potential disruptions.
Parker completed its 25th solar pass in September, matching a record distance of 3.8 million miles (6.2 million kilometers) from the sun’s surface, according to NASA. The spacecraft also matched its record speed of 427,000 miles per hour (687,000 km/h), making it the fastest man-made object in history. The speed and distance records were first set in December 2024 and were tied in three subsequent flybys (March, June, and September 2025).
Although Parker’s main mission has ended, the rover remains in good condition and will continue collecting data until at least mid-2029.
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