It is so easy to take the Sun for granted. It shines brilliantly and defines our days, and it provides the warmth that nurtures life on Earth. But even after centuries of study, it has been reluctant to give up many of its mysteries.

 

We know the Sun is an enormous fusion reactor, changing hydrogen into helium and creating massive amounts of energy that produce wide-ranging impacts on all the worlds of the Solar System. However, we don’t know much about the Sun’s atmosphere, and we have very little understanding of how and when it creates solar weather – including dangerous solar flares and coronal mass ejections of plasma, magnetic fields, and energetic particles.

The Sun emits enormous energy from sunspots, captured here with X-ray photography from the NuSTAR satellite. Image credit: NuSTAR, SDO, NASA

Risks of Solar Weather

While Earth is protected by the magnetosphere from the worst effects of solar weather, objects in orbit – including astronauts – are at risk. GPS systems and the electronic circuits of other communication satellites can get knocked out of commission. Even power grids can fail under the impact of intense solar energy.

“A huge solar event could cause $2 trillion in damage to the U.S. alone, and the Eastern Seaboard . . . could be without power for a year.” – The Johns Hopkins University Applied Physics Laboratory

Exploring the edge of the Sun’s outer shell – its photosphere – and gauging its internal processes up close have been top priorities of the scientific community for more than half a century. But major hurdles have stood in the way of sending a mission to the Sun, not the least of which is that it is really hot up there – a metal-melting three million degrees Fahrenheit! What could operate in that neighborhood without being vaporized into space dust?

And even if a craft were created that could survive such extreme conditions, how would scientific instruments be able to gather and send back data from the solar atmosphere?

Predicting Solar Storms

Questions such as these have been posed at least since 1958, when Eugene Parker, a University of Chicago astrophysicist, predicted the existence of solar winds, those streams of charged particles that blow incessantly from its outermost layer.

 

Well, NASA is always up for a challenge. Over the years since Parker’s prediction, the agency has steadily been working on solutions to the problems associated with a solar flight.

 

Enlisting the support of other institutions – notably The Johns Hopkins University’s Applied Physics Laboratory (APL) – NASA recently announced plans for the first mission to send a spacecraft close to the solar corona, the aura of plasma that surrounds the Sun, for a series of unprecedented tests.

Artist’s conception of the Parker Solar Probe spacecraft as it approaches the Sun. Image credit: Johns Hopkins University Applied Physics Laboratory

The Parker Solar Probe Takes Off

This mission, called the Parker Solar Probe, is scheduled for launch in the summer of 2018, and will take seven years to get into position for its closest fly-by of the edge of the Sun’s photosphere. At its nearest approach, it will experience temperatures of 2,500 degrees Fahrenheit and radiation 475 times higher than that on Earth.

 

How will the probe survive such conditions? Success will require a nearly miraculous fusion of materials and construction techniques. Johns Hopkins’s APL, which is designing and building the spacecraft, and will operate it, has devised a super-protective shield made of a 4.5-inch-thick carbon composite. The shield will not only protect the exterior from harm, it will be able to maintain the scientific instruments within the spacecraft at near-room temperature.

The goals of the Parker Solar Probe are ambitious but simple:

  • Explore how energy and heat move through the Sun’s corona; and
  • Examine the process that accelerates the solar wind and solar particles.

“Suites” of correlated instruments will not only investigate magnetic fields, plasma, and energetic particles, but also actually image the solar wind, a feat that has never been accomplished from such a close perspective.

The TRACE satellite captured this image showing the great heat generated as the Sun’s corona lifts loops of plasma above its photosphere. Image credit: M. Aschwanden et al. (LMSAL), TRACE, NASA

Grazing the Sun’s Atmosphere

Over its seven-year active life, the probe will perform seven increasingly close fly-bys and 28 orbits around the Sun. It will use the gravitational field of Venus to springboard ever closer to the Sun, and will eventually be 10 times closer to the Sun – 3.7 million miles – than its nearest planet, Mercury.

The probe is expected to produce significant advances in our knowledge of the solar environment. One goal of the mission will be to study the 11-year cycle of the Sun’s magnetic field as it progresses from relatively quiet periods of surface activity through periods of rapid sunspot creation and back to quiet again. A better understanding of the cycle will greatly aid in predicting when we can expect solar flares to send potentially damaging streams of energy toward Earth.

“The solar probe is going to a region of space that has never been explored before. It’s very exciting that we’ll finally get a look. . . . I’m sure that there will be some surprises. There always are.” – astrophysicist Eugene Parker

A Safer Sun

We live in the atmosphere of the Sun and are subject to solar weather all the time. Getting a better handle on the physics of its corona, outer atmosphere, and interior will increase our appreciation of the Sun’s relation to the Earth and other planets. It will also help us improve satellite communications and the reliability of power grids, protect against radiation exposure on airline flights, and advance our ability to keep astronauts safe during prolonged space flights.

We all want to feel safe in the light of the Sun. NASA’s goal is to make the Sun safer for all of us.

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