NASA Launches Solar Probe

TOPICAL SCIENCE

AUTHOR: M. FRANKLIN

A U G U S T

AUGUST 2018

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Topical Science

NASA Launches Solar Probe Contents

Page 1. Intro & Image of our sun Page 2. The Parker solar probe Page 3. Journey to the Sun Page 4. Our Sun

Image of our Sun The Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory captured its 100 millionth image of the sun on Jan. 19, 2015.

The dark areas at the bottom and the top of the image are coronal holes -- areas of less dense gas, where solar material has flowed away from the sun.

Credit: NASA/SDO/AIA/LMSAL

Key Dates Proposed Launch Date

First flyby of Venus

First close approach to the sun

August 6th 2018

September 2018

December 2024

Introduction This month, NASA will launch a new mission, the Parker Solar Probe, that will go closer to the sun than ever before.

The sun is our closest star and provides us with heat, light and energy. By studying the sun, we can learn about the processes that occur in similar stars, many light years away from us.

However, because of the intense heat and radiation to which the probe will be exposed, the mission presents many technical challenges.

TOPICAL SCIENCE

AUGUST 2018

The Parker Solar Probe The Mission This is not the first solar probe that NASA has launched, but it will go closer to the sun than ever before. Its main scientific goals are: 1. To discover the cause of the extremely high temperature of the sun’s outer atmosphere, known as the ‘corona’; 2. To examine the magnetic fields that give rise to the so called ‘solar wind’; 3.To explore the plasma near the sun & its influence on the solar wind; 4. To determine the mechanisms that accelerate and transport energetic particles.

The Parker Solar Probe at the Astrotech spacecraft processing facility in Titusville, Florida. Credit: NASA/Johns Hopkins APL/Ed Whitman

Who is Parker?

Professor Eugene Parker Credit: University of Chicago

The mission has been named after Eugene Parker, Chandrasekhar Distinguished Service Professor Emeritus, Department of Astronomy and Astrophysics at the University of Chicago. In the 1950s, Parker proposed a theory of how the Sun and stars give off energy. He described the solar wind, as well as the system of plasmas, magnetic fields and high-energy particles that are produced in the solar atmosphere. He also attempted to explain the extremely high temperature of the sun’s corona.

Is the probe in danger of melting?

The Parker Solar Probe has 4½-inch-thick carbon-composite solar shields that can withstand the high temperature as it approaches the sun up to a 2,500 degrees Fahrenheit. Eugene Parker finds the mission to be another revolutionizing event for the astronomy world. “The solar probe is going to a region of space that has never been explored before,” Parker informed CNN. “It’s very exciting that we’ll finally get a look. One would like to have some more detailed measurements of what’s going on in the solar wind. I’m sure that there will be some surprises. There always are.”

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TOPICAL SCIENCE

AUGUST 2018

Journey to the Sun The Parker probe will take over six years to reach its closest approach to the sun. It will fly by Venus seven times, using the planet’s gravity to assist it to gradually reduce the size of its elliptical orbit around the sun. At its final perihelion, the probe will reach a speed of about 200 km/s, making it the fastest man-made object ever. This means it will not remain close to the sun for a long period and it will slow down as it moves away from the sun and approaches aphelion.

According to NASA, the data and observations obtained from the mission may provide sound knowledge about the physics of the stars, profound details about the sun’s corona, and understanding about solar wind which will help improve the forecasting of major space weather events.

“We’ve been inside the orbit of Mercury and done amazing things, but until you go and touch the sun, you can’t answer these questions,” said Nicola Fox, Parker Solar Probe project scientist at Johns Hopkins Applied Physics Laboratory via CNN. “Why has it taken us 60 years? The materials didn’t exist to allow us to do it. We had to make a heat shield, and we love it. Something that can withstand the extreme hot and cold temperature shifts of its 24 orbits is revolutionary The sketch shows the trajectory that the Parker Solar Probe will follow, on its journey to the sun.

It will cross the orbits of Venus and Mercury several times, in its evershrinking elliptical orbits.

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TOPICAL SCIENCE

AUGUST 2018

Our Sun The sun is our nearest star. Like all stars, it is a massive ball of hot gas, in the ionised state, known as plasma. The gas is held together by the force of gravity.

Most of the material of the sun consists of the element hydrogen. But because of the high temperature, these hydrogen atoms have become ionized, as they have lost their negatively charged electrons. The nuclei of hydrogen atoms are tiny positively charged particles called protons. Such a hot ionized gas is known as plasma. We have three states of matter on our planet earth; solid, liquid and gas. Plasma is a fourth state that occurs only at extremely high temperatures, such as in the stars.

The sun’s gravity produces enormous pressure in its centre and this, along with the high temperature, causes thermonuclear fusion to occur. In this process, four protons fuse to form helium nuclei, releasing enormous amounts of energy. The mass of a helium atom is slightly less than the combined masses of four protons. A great amount of energy is produced because the ‘missing’ mass is converted into energy, according to Einstein’s famous equation: E = MC^2.

Thermonuclear fusion is responsible for the sun’s energy output.

The temperature difference between the sun’s interior and its surface causes convection currents, while the sun’s rotation makes the plasma swirl around, with different parts of the sun rotating at different speeds. This turbulent motion of charged plasma creates strong fluctuating magnetic fields, whose lines of force create loops in the sun’s outer atmosphere, known as the corona. Closed magnetic loops cause a slight cooling in places, which appear as darker sunspots on the bright surface. When the sun becomes more active, more sunspots appear. While the magnetic fields are stable, they confine the plasma. But as energy builds up, the loops occasionally break, releasing up to a billion tons of material in what is known as a coronal mass ejection (CME), which sends streams of charged particles out into space. All of this is known, but the extremely high temperature of the sun’s corona is still a puzzle to scientists. It is hoped that the Parker Solar Probe will provide answers to some of the questions, about out sun, that still remain.

The Author Margaret Franklin is a retired chemistry lecturer.

She spent most of her career at Athlone Institute of Technology, in the Midlands of Ireland. For several years, Margaret wrote a column entitled ‘Topical Science’ for a local weekly newspaper. It is now published on-line as a monthly newsletter, covering science topics for the information of the general public.

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