Nasa's hotly anticipated solar mission renamed to honour astrophysicist Eugene Parker

Renamed the Parker Solar Probe to honour solar astrophysicist who predicted high speed solar wind, the spacecraft will attempt to get close to sun’s surface

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.

The Parker Solar Probe's mission

It is not the first time that Nasa has renamed a mission to honour a scientist. In 2008 the space agency renamed the Gamma-ray Large Area Space Telescope as the Fermi Gamma-ray Space Telescope in honour of the late Italian physicist Enrico Fermi. In 2012, the space agency announced that it was renaming the Radiation Belt Storm Probes in honour of the late James Van Allen. Van Allen discovered two radiation belts composed of charged particles, known as the Van Allen belts, that encircle the Earth.

“Nasa has never named a spacecraft after a researcher during their lifetime. Well, ladies and gentlemen, we are about to make history,” said Thomas Zurbuchen, associate administrator of the Nasa science mission directorate, announcing the new name of the mission at the University of Chicago.

Speaking at the press conference Nicola Fox, mission project scientist at the Johns Hopkins University Applied Physics Laboratory, added that a chip would be placed on board the spacecraft carrying pictures of Parker and his scientific papers, as well as a plate with an inscription of his choice. Parker was then presented with a model of the probe.

In addition, Parker was awarded with the Nasa Distinguished Public Service Medal – the highest award from the space agency for non-governmental personnel – in honour of his lifetime’s work.

Dressed in a black suit and tie, Parker said that he was privileged that the mission had been named after him. “I am greatly honoured to be associated with such a heroic scientific space mission,” he said, explaining that designing a spacecraft to withstand temperatures so close to the sun is a considerable feat.

Realising a dream from the beginning of the space age

The size of a car, shaped like the business end of a torch, and built to withstand temperatures of more than 1400C (2552F), the newly named Parker Solar Probe is set to be launched next summer in an unprecedented attempted to get up close to our star, coming within 4m miles of its surface.

“It is just extraordinary - it is something that people have wanted to do from the beginning of the space age,” said Tim Horbury, professor of physics at Imperial College London.

Scientist say the mission, costing in the region of $1.5bn, could radically change our understanding of the sun, while offering vital insights into space weather - phenomena including coronal mass ejections that trigger geomagnetic storms that not only damage satellite systems but can knock out power grids on Earth.

“It is just a hugely important and scientifically fascinating mission,” said David McComas, vice president of the Princeton University plasma physics laboratory and principal investigator for the probe’s “Integrated Science Investigation of the sun”, research that will probe how electrons, protons and other charged particles are accelerated in the sun’s atmosphere.

An artist’s impression of the Parker Solar Probe spacecraft approaching the sun.
An artist’s impression of the Parker Solar Probe spacecraft approaching the sun. Photograph: Johns Hopkins University Applied/PA

“It is far closer than anything ever built by humanity has ever gotten to the sun,” McComas said.

Instruments for a number of scientific investigations on board the spacecraft will probe myriad solar phenomena from the electric and magnetic properties of the sun’s plasma to counting and catching the components of solar wind. The latter, a project dubbed the Solar Wind Electrons Alphas and Protons Investigation, is led by Kasper.

“The sun is obviously very hot – its outer atmosphere is at hundreds of thousands of degrees Kelvin, and as a result it blows a bubble into interstellar space,” said Horbury. “We live in that bubble, we live in the heliosphere, and it is the solar wind that blows that bubble.”

The goal of the probe is to understand how the sun makes the solar wind, and explore the physical process that are occurring. A member of the science team for the probe’s Fields instrument, Horbury plans to study turbulence within the solar wind.

“When we first started [looking at the sun from space] that we realised the sun is not a boring yellow sphere, it is an incredibly dynamic, active plasma object,” he said.

But the challenges have been immense, Horbury adds, describing the mission as “just on the edge of achievable”. The major difficulty was designing the probe to prevent it being toasted by the sun’s immense heat - as part of the solution the probe boasts a large heat-shield that is actively cooled by radiator systems.

“There is a tiny spacecraft cowering behind this big heat shield,” Horbury said. “It is just extreme - everything is different when you are that close in [to the sun].”

The Parker Solar Probe will travel far closer to the sun that any previous probe. While 4m miles might sound like a sizeable distance from the sun, it corresponds to under 10 solar radii. “[The Earth is] about 250-odd solar radii away, so it is really close,” said Horbury.

Nasa launches Iris mission to explore solar energy

The distance is crucial. Solar wind accelerates away from the sun, but it is about 10 solar radii that it effectively goes supersonic. “The point about the probe is it is going to get within that critical point,” said Hornbury.

McComas’s part of the mission will explore in detail how certain particles, ejected by events including coronal mass ejections but not part of the solar wind, end up with very high energies, travelling at speeds of up to 80% of the speed of light. “They are really interesting and important particles because, for example, they can cause radiation damage in space to spacecraft, they can be a threat to astronauts in space,” he said.

The mission is not only expected to offer unprecedented insights into the physics of the sun – an endeavour that will shed light on processes happening in stars across the universe – but will also yield vital information about space weather, that could help scientists to predict major events before they affect Earth.

The stakes for the mission are high, admits Horbury.

“The thing about space is everyone has done the easy stuff – we are only left with the difficult things, so by definition this is risky,” he said. “They are really pushing the limits of what is possible. But that is the way you make progress.”


Nicola Davis

The GuardianTramp

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