The U.S. space agency NASA says its Parker Solar Probe this week became the first spacecraft to enter the Sun’s atmosphere, also known as the corona. 

The space agency announced the news Tuesday at a press conference during a meeting of the American Geophysical Union in New Orleans. 

In a statement, NASA scientists said the probe actually entered the Sun’s corona April 18, but it took until now to get the data and examine it to confirm it had accomplished its mission. 

NASA said while the Sun doesn’t have a solid surface, it does have a superheated corona made of solar material bound to the Sun by gravity and magnetic forces. The point at which those forces are too weak to contain material ejected from the sun is considered the edge of the corona, an area scientists call the Alfvén critical surface. 

NASA says the Parker probe crossed this boundry about 13 million kilometers above the surface of the sun. Until they were able to examine the data from the probe, scientists were not exactly sure where the area was. 

The scientists say during the flyby, which lasted only a few hours, the solar probe passed into and out of the corona several times. The data it gathered in doing so proved what some had predicted — that the Alfvén critical surface isn’t shaped like a smooth ball, but has it has spikes and valleys that wrinkle the surface. 

The Parker Solar Probe was launched in 2018 and was intended to exactly what it is doing: flying closer to the sun than any spacecraft has done before. NASA scientists compare what the probe has accomplished to landing on the moon. As the mission continues, the agency says, it will help scientists uncover critical information about Earth’s closest star and its influence on the solar system. 

A paper on the achievement was also published Tuesday in the scientific journal Physical Review Letters. 

Some information for this report was provided by the Associated Press.
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