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The Coolest, Hottest Mission to the Sun
In August 2018, NASA’s Parker Solar Probe launched to space, soon becoming the closest-ever spacecraft to the Sun. With cutting-edge scientific instruments to measure the environment around the spacecraft, Parker Solar Probe – designed, built, and managed for NASA by the Johns Hopkins Applied Physics Laboratory – has completed six of 24 planned passes through never-before-explored parts of the Sun’s atmosphere, the corona.
And this bold mission of discovery is just getting started.
“We’ve learned a great deal about our star in the past several decades, but we needed a mission like Parker Solar Probe to go into the Sun’s atmosphere,” said Nour Raouafi, Parker Solar Probe project scientist at APL. “It’s only there that we can really learn the details of these complex solar processes. And what we’ve learned [so far] has changed a lot of what we know about the Sun.”
Taking the Heat
Making Parker Solar Probe possible are key technologies developed by APL. A revolutionary 4.5-inch-thick (11.43 centimeters) carbon-composite thermal protection system – or heat shield – keeps the spacecraft and most of its instruments at a comfortable 85 degrees Fahrenheit, even as the spacecraft plunges deeper into the Sun’s fiery corona.
The solar-powered spacecraft houses active water-cooled solar arrays (a first in space) that retract and extend as Parker Solar Probe swings toward or away from the Sun, making sure the panels stay at appropriate temperatures while providing the necessary power to operate the spacecraft and instruments autonomously. At its closest passes the spacecraft must survive temperatures of up to 2,500 degrees F, and solar intensity of about 500 times what we experience here at Earth on the hottest day of the year.
On each orbit, Parker Solar Probe sets records for speed and solar distance. On its last close approach to the Sun (called perihelion) on Sept. 27, the spacecraft came within 8.4 million miles (13.5 million kilometers) of the Sun’s surface — less than one-tenth of the distance between Earth and the Sun — while reaching a top speed of 289,927 miles per hour (466,592 kilometers per hour). The probe will ultimately dip inside 4 million miles of the solar surface, while moving 430,000 miles per hour.
The Sun-Earth Connection
The information Parker Solar Probe has already uncovered about how the Sun constantly ejects material and energy will help scientists retool the models we use to understand and predict the space weather around our planet and understand the process by which stars are created and evolve.
“Observing the Sun from up close, rather than from a much greater distance, is giving us an unprecedented view into important solar phenomena and how they affect us on Earth, and gives us new insights relevant to the understanding of active stars across galaxies” said Thomas Zurbuchen, NASA’s associate administrator for science. “It’s just the beginning of an incredibly exciting time for heliophysics with Parker Solar Probe in the vanguard of new discoveries.”
Solar mysteries: Parker Solar Probe has observed switchbacks — traveling disturbances in the solar wind that causes the magnetic field to bend back on itself — an as-yet unexplained phenomenon that might help scientists uncover more information about how the solar wind is accelerated from the Sun.
Credit: NASA GSFC/Adriana Manrique Gutierrez
Our magnetically active Sun unleashes powerful bursts of light, deluges of particles moving near the speed of light and billion-ton clouds of magnetized material. All of this activity affects our planet, injecting damaging particles into the space where our satellites and astronauts fly, disrupting communications and navigation signals, and even — when intense — triggering power outages.
Most of the material that escapes the Sun is part of the solar wind, a continual outflow of solar material that bathes the entire solar system. This ionized gas, called plasma, carries with it the Sun's magnetic field, stretching it out through the solar system in a giant bubble – the heliosphere – that spans more than 10 billion miles.
"We are starting to get some of the missing pieces of the coronal puzzle, like glimpses of how the solar wind behaves, but there is still more to explore and observe in the next several years as Parker Solar Probe gets closer and closer to the Sun,” said Rob Decker, Parker Solar Probe deputy project scientist at APL. “Parker Solar Probe is opening our eyes to a new reality of the corona and solar wind."
Earlier this year, scientists released a new wave of Parker findings in an Astrophysical Journal supplement, Early Results from Parker Solar Probe: Ushering a New Frontier in Space Exploration. The collection of nearly 50 papers covers data from the first three solar flybys, and builds upon initial results released in the journal Nature and discussed at the American Geophysical Union meeting in December 2019.
Eugene Parker, professor emeritus at the University of Chicago, visits the spacecraft that bears his name, in October 2017. Engineers in the clean room at APL, which built and now operates Parker Solar Probe, point out the instruments that will collect data as the mission travels directly through the Sun’s atmosphere.
Credit: NASA/Johns Hopkins APL/Ed Whitman
More to Come
As Parker Solar Probe continues on its journey, it will make 18 more close approaches to the Sun at progressively closer distances, culminating in three orbits a mere 3.83 million miles from the solar surface.
“The Sun is the only star we can examine this closely,” said Nicola Fox, director of the Heliophysics Division at NASA Headquarters. “Getting data at the source is already revolutionizing our understanding of our own star and stars across the universe. Our little spacecraft is soldiering through brutal conditions to send home startling and exciting revelations.”
Adapted from an article by Sarah Frazier, NASA’s Goddard Space Flight Center
Engineers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, lower the thermal protection system – the heat shield – onto the Parker Solar Probe spacecraft for a September 2017 alignment test.
Credit: NASA/Johns Hopkins APL/Ed Whitman
Members of the Parker Solar Probe team examine and align one of the two solar arrays that will power the spacecraft during its seven-year mission to the Sun. The solar arrays are cooled by a gallon of water that circulates through small tubes in the arrays and into large radiators at the top of the spacecraft.
Credit: NASA/Johns Hopkins APL/Ed Whitman