Nasa has announced its hotly anticipated mission to send a spacecraft into the sun’s outer atmosphere has a new name.
Formerly known as the Solar Probe Plus mission, the endeavour will now be known as the Parker Solar Probe, honouring the American solar astrophysicist Eugene Parker who predicted a high speed solar wind – the stream of charged particles, or plasma, that flows from the sun out into space.
Parker, a professor emeritus at the University of Chicago who will turn 90 on 10 June, put forward his theory in 1958. It was initially met with scepticism. “People just thought it was crazy,” said Justin Kasper, a space scientist at the University of Michigan and lead investigator for one of the probe’s scientific research projects. But later observations proved the prediction correct.
Parker’s work delved into a longstanding puzzle. While the temperature at the centre of the sun is about 15mC, further out things get complicated. “One of the mysterious things about our sun’s atmosphere is the [sun’s] surface, which is glowing visible in the yellow and white, is 6,000C, but the corona – its atmosphere – is at 1m-5mC,” said Kasper.
The incredible temperatures in the corona, Parker realised, would create an unstable situation, meaning the sun’s atmosphere is no longer pulled back by the star’s gravity but instead escapes into space.
“Parker said that by a couple of solar radii, the atmosphere would hit the speed of sound, it would break the sound barrier in the sun’s atmosphere, [and] by 10 solar radii it would be going supersonic,” said Kasper. “We enter the space age, and one of the first things we discover is this supersonic solar wind.”
With the probe set to investigate the origins of solar wind, including the mysterious heating of the sun’s atmosphere and how the solar wind accelerates to astonishing speeds of up to 400 miles per second, the renaming of the mission is a fitting tribute to Parker.
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