University of Minnesota scientists part of mission to ‘touch the sun’

August 10, 2018
NASA’s Parker Solar Probe

This illustration of the Parker Solar Probe shows it approaching the Sun.

Credit: NASA/Johns Hopkins APL/Steve Gribben

Experiments designed by University of Minnesota space physicists and colleagues across the country will fly to the sun aboard NASA’s Parker Solar Probe, scheduled for launch on Saturday, Aug. 11, 2018.

The University physicists and their colleagues make up the FIELDS team, one of four teams chosen to design suites of scientific instruments for the Parker Solar Probe.

Swooping closer to the sun than any previous mission, the Parker Solar Probe will explore the star’s corona (atmosphere) to solve its two biggest mysteries. The first quest is to find the mechanism that heats the corona to more than 100 times the temperature of the solar surface. The second is to identify the coronal dynamo that accelerates subatomic particles from the sun’s surface to speeds up to a million miles per hour and spews them out in a 3-D stream that bathes the solar system. That phenomenon is known as the solar wind.

“It’s a dream mission,” said physics professor Keith Goetz, the principal investigator for the University’s Parker Solar Probe team. “It’s the most interesting thing in space physics. Understanding how nature works is our big thing in physics, but so is understanding how the world around us works.” 

For example, when pointed at Earth, the solar wind’s most energetic outbursts endanger power grids and astronauts. The Parker Solar Probe will fly to the region of the corona where solar wind particles are accelerated; data collected there will help explain the genesis of the solar wind, making it easier to predict and take precautions against its strongest gales.    

NASA named the probe for solar physicist Eugene Newman Parker, who, among other revolutionary contributions, predicted the discovery of the solar wind.

Grazing the sun
The Parker Solar Probe is designed to be the fastest vehicle ever built.

The size of a small car, the spacecraft will perform seven flybys of Venus, tapping the planet’s gravity to steer itself ever nearer to the sun. At its closest, it will sail through the corona at speeds topping 400,000 miles per hour, fast enough to get from New York to Tokyo in under a minute. 

At closest approach, the Parker Solar Probe will plunge within four million miles of the sun’s core—eight times closer than Mercury. As NASA puts it, if the Earth and the sun were at opposite goal lines on a football field, the Parker Solar Probe would reach the sun’s four-yard line. The closest any previous spacecraft has come is the 29-yard line.

“It’s one of the most challenging missions NASA has ever tried to do,” said University of Minnesota physics professor and Parker Solar Probe team member John Wygant. “The spacecraft’s carbon-ceramic heat shield has to withstand temperatures as high as 2,550 degrees Fahrenheit.”

That, said Goetz, is what we would feel on a beach under 500 suns—enough heat to melt steel.

More on the mysteries
With the sun’s surface temperature hovering around 10,000 degrees Fahrenheit, particles destined for the solar wind ought to cool off as they escape to the corona. Instead, they are heated to a few million degrees. Thus, some mechanism must exist to transfer energy to the corona, where it is dissipated as heat.

“Whatever heats the corona has to be electric and magnetic fields. That’s all there is,” Goetz said. “There are competing ideas about the details, but no measurements or observations.”

As for the dynamo that accelerates the particles to form the solar wind, electric and magnetic fields are again implicated.

“The Parker Solar Probe lets us finally make the measurements we need to settle the debate about coronal heating and understand why the solar wind blows so fast,” Goetz said.

A FIELDS day for physics
The University of Minnesota’s role in the FIELDS experiments centers on the time domain sampler, or TDS, an instrument Goetz designed to measure electric and magnetic fields, radio waves, and abundances and sizes of interplanetary dust particles. This “souped-up car radio,” as he calls it, also periodically sifts its stored data and saves only what seems most promising or intriguing.

Other University of Minnesota FIELDS members are physics professor Cynthia Cattell and retired professor Paul J. Kellogg. The principal investigator for FIELDS is University of California Berkeley physics professor Stuart Bale, who received his bachelor’s and Ph.D. degrees from the University of Minnesota.

“I think this mission will be epochal. The solar corona is one of the most important places in the solar system we’ve never visited,” Bale said. “Also, as happens whenever we develop cutting-edge instrumentation and send it into space, I expect we’ll have a few exciting surprises.”

Other institutions involved in FIELDS are the Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder; NASA Goddard Space Flight Center; the University of Maryland, College Park; the University of New Hampshire; l’Observatoire de Paris, Meudon; le Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E); and the Smithsonian Institution.

Parker Solar Probe is part of NASA’s Living With a Star program to explore aspects of the sun-Earth system that directly affect life and society. LWS is managed by the agency’s Goddard Space Flight Center in Greenbelt, Md., for NASA’s Science Mission Directorate in Washington, D.C. The Johns Hopkins University Applied Physics Laboratory manages the mission for NASA. It designed and built, and will operate the spacecraft.

For more information and multimedia, visit the NASA website.

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