A spacecraft is due to head for the sun this month. This Parker Solar Probe will be the first to swoop through our star’s outer atmosphere.
It will whip around the sun two dozen times over the next seven years. At its closest, it will skim within some 6 million kilometers (4 million miles) of the star’s surface. That’s more than seven times as close as any previous spacecraft. At its nearest, Parker will hurtle through the outer atmosphere. That’s known as the sun’s corona.
Parker will zip through the corona at about 700,000 kilometers (435,000 miles) per hour. That’s fast enough to skip from Philadelphia to Washington, D.C., in about one second. Indeed, Parker will become the fastest human-made object in the solar system.
The probe is being dispatched to make closeup observations of the corona and the solar wind. That “wind” is a torrent of charged particles that the star constantly flings into space. Both observations could help resolve long-standing mysteries about the inner workings of the sun’s atmosphere. And the new data may improve forecasts for space-weather events, such as solar flares. Such flares can endanger spacecraft, astronauts — even technology on Earth.
Craig DeForest is not involved in the Parker mission. But he finds the mission “phenomenal.” DeForest works at the Southwest Research Institute in Boulder, Colo., where he studies the physics of the sun. The trove of new data gathered by the probe “is going to answer a lot of questions that we couldn’t answer in any other way,” he says. “There’s been a tremendous amount of anticipation for it.”
Setting sights on the sun
Researchers have had a probe like Parker on their wish lists for nearly 60 years. NASA was created in 1958. That same year, the Space Studies Board of the National Academies of Science and of Engineering recommended that the new agency send a spacecraft inside the orbit of Mercury. The goal was to investigate the environment about the sun.
Over the years, other research groups have floated the idea of sending missions to explore the sun. But none of these would get as close to the sun as astronomers wanted. Only recently has technology emerged to make a close-up mission possible, DeForest says.
The Parker Solar Probe is about the size of a small car. It will house instruments to take 3-D images of the sun’s atmosphere. It also will measure our star’s electric and magnetic fields. And it will catalog high-energy particles. To do these things, the craft will swoop through the sun’s corona, which sizzles at up to 10 million degrees Celsius (18 million degrees Fahrenheit). But it’s the sun’s surface that poses the greatest danger to the probe. Its lethally intense sunlight can heat the face of the spacecraft to about 1,370 °C (2,498 °F).
The Parker probe has some safeguards, though. It is armed with a heat shield. This is a layer of carbon foam sandwiched between panes of another carbon-based material. That’s similar to material used to make golf clubs and tennis rackets. As Parker swings around the sun, this heat shield will continuously face the star. It will protect the instruments tucked behind it. There they will be safe from radiation up to 475 times as intense as what Earth-orbiting spacecraft endure.
Parker will dive into the sun’s corona for the first time in November 2018. It will send its first batch of data back to Earth in early December. For scientists, that’s pretty quick gratification. When a spacecraft called New Horizons rocketed to Pluto, it took years to reach the icy dwarf planet.
The Parker probe will circle the sun 24 times. It will use the gravitational pull of Venus to gradually shrink its orbit around the sun. On its first go-round this coming November, Parker will fly within 24 million kilometers (15 million miles) of the sun’s surface. On its final loop in 2025, the probe will get within about 6 million kilometers (4 million miles).
By then, the probe may have some fuel left over. If so, it will keep cruising around the sun. Eventually, though, Parker won’t be able to fire the thrusters that it uses to keep its heat shield aimed at the sun. From then on, the probe “will start to turn,” says Nicola Fox. She is the project scientist for the Parker Solar Probe mission. “Bits of the spacecraft that are totally not designed to see the sun will be in full illumination,” she explains. “The spacecraft will break up into kind of large chunks, at first. And then they’ll get smaller and smaller.” Eventually, she says, Parker will be nothing more than a smattering of dust scattered across the sun’s corona.
The spacecraft’s legacy, however, will live on in solar science. Data from Parker could explain the strange temperature difference between the surface of the sun and the corona. The surface is a toasty 5,500 °C (9,932 °F). The corona is millions of degrees. That’s quite a jump in temperature. And it may be due to vibrating magnetic field lines. They could heat the material in the corona. Or jets of material from the sun’s surface might inject energy into its atmosphere. Parker should also provide clues to the speed of solar wind particles. It’s not yet clear where the particles get the energy needed to speed up and escape the sun’s immense gravitational pull.
The mysterious heat of the corona and the speed up of the solar wind probably have a common cause, says David McComas. He is physicist at Princeton University in New Jersey. He studies space plasma, which is made of charged particles. McComas is the principal investigator for two instruments on Parker. The instruments are known as the Integrated Science Investigation of the Sun. They will monitor high-energy particles in the solar atmosphere.
The solar wind washes over Earth at hundreds of kilometers per second. Disturbances in this cosmic breeze can mess with satellites, spacecraft and Earth’s electric-power grids. Parker will give scientists a better understanding of the sun’s turbulent atmosphere. It also will reveal secrets of the solar wind. Both could lead to better forecasts for potentially dangerous space weather events.
Parker’s zoomed-in view of the sun undoubtedly will also raise new mysteries about our home star, McComas says. The data haul from “one mission [often] just whets our appetites for even more observations down the road,” he says.
Fortunately, another spacecraft is also bound for the sun. This, the European Space Agency’s Solar Orbiter, is set to take flight in 2020. This craft will provide the first direct images of the sun’s poles. Those observations will be paired with Parker’s close view of the sun’s midriff. Together, these data could reveal how the solar wind varies at different latitudes.
These missions aren’t just about getting to know our sun. “Once you know about how our star works, you’re going to know a lot more about how other stars [do too],” Fox says. She studies the physics of the sun at the Johns Hopkins Applied Physics Laboratory in Laurel, Md.
“This is really freaking cool,” DeForest says. “We’re launching a probe and flying it through [several]-million-degree plasma on the periphery of a star. I mean, how cool is that?”
3-D Short for three-dimensional. This term is an adjective for something that has features that can be described in three dimensions — height, width and length.
astronaut Someone trained to travel into space for research and exploration.
astronomy The area of science that deals with celestial objects, space and the physical universe. People who work in this field are called astronomers.
atmosphere The envelope of gases surrounding Earth or another celestial body.
carbon The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
corona The envelope of the sun (and other stars). The sun’s corona is normally visible only during a total solar eclipse, when it is seen as an irregularly shaped, pearly glow surrounding the darkened disk of the moon.
cosmic An adjective that refers to the cosmos — the universe and everything within it.
data Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.
dwarf planet One of the solar system’s small celestial objects. Like a true planet, it orbits the sun. However, dwarf planets are too small to qualify as true planets. Prime examples of these objects: Pluto and Ceres.
engineering The field of research that uses math and science to solve practical problems.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).
field (in physics) A region in space where certain physical effects operate, such as magnetism (created by a magnetic field), gravity (by a gravitational field), mass (by a Higgs field) or electricity (by an electrical field).
grid (in electricity) The interconnected system of electricity lines that transport electrical power over long distances. In North America, this grid connects electrical generating stations and local communities throughout most of the continent.
latitude The distance from the equator measured in degrees (up to 90).
magnetic field An area of influence created by certain materials, called magnets, or by the movement of electric charges.
magnetic field lines The lines that surround a magnet (you can see this if you drop iron filings around the edges of a bar magnet).
Mercury (in astronomy) A rocky planet and the one whose orbit is closest to the sun. (Here, the term is capitalized.)
monitor To test, sample or watch something, especially on a regular or ongoing basis.
NASA Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.
orbit The curved path of a celestial object or spacecraft around a star, planet or moon. One complete circuit around a celestial body.
orbiter A spacecraft designed to go into orbit, especially one not intended to land.
particle A minute amount of something.
physicist A scientist who studies the nature and properties of matter and energy.
physics The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. Quantum physics, a field of study that emerged later, is a more accurate way of explaining the motions and behavior of matter. A scientist who works in such areas is known as a physicist.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood.
plasma (in chemistry and physics) A gaseous state of matter in which electrons separate from the atom. A plasma includes both positively and negatively charged particles.
Pluto A dwarf planet that is located in the Kuiper Belt, just beyond Neptune. Pluto is the tenth largest object orbiting the sun.
poles (in Earth science and astronomy) The cold regions of the planet that exist farthest from the equator and that serve as the upper and lower ends of the virtual axis around which a celestrial object rotates.
radiation (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
satellite A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.
solar flare An explosive event that takes place on the sun when energy that has built up in 'twisted' magnetic fields (usually above sunspots) becomes suddenly released. The energy can in minutes heat to many millions of degrees, emitting a burst of energy. That energy consists of radiation across the electromagnetic spectrum, from gamma rays to radio waves.
solar system The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
solar wind A flow of charged particles (including atomic nuclei) that have been ejected from the surface of the star, such as our sun. It can permeate the solar system. This is called a stellar wind, when from a star other than the sun.
space weather Conditions on the sun, in the solar wind and within Earth’s upper atmosphere that can affect technologies on Earth and that have the potential to endanger human health. Triggering these weather events are the stream of plasma, or solar wind, emitted by the sun. In addition, there are clouds of material spewed by the sun, known as coronal mass ejections. Together, these can contribute to large magnetic and electrical storms in Earth’s upper atmosphere.
star The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.
sun The star at the center of Earth’s solar system. It’s an average size star about 26,000 light-years from the center of the Milky Way galaxy. Also a term for any sunlike star.
technology The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.
thruster An engine that pushes or drives with force by expelling a jet of fluid, gas or stream of particles.
trove A collection of valuable things.
turbulent (n. turbulence) An adjective for the unpredictable fluctuation of a fluid (including air) in which its velocity varies irregularly instead of maintaining a steady or calm flow.
Venus The second planet out from the sun, it has a rocky core, just as Earth does. Venus lost most of its water long ago. The sun’s ultraviolet radiation broke apart those water molecules, allowing their hydrogen atoms to escape into space. Volcanoes on the planet’s surface spewed high levels of carbon dioxide, which built up in the planet’s atmosphere. Today the air pressure at the planet’s surface is 100 times greater than on Earth, and the atmosphere now keeps the surface of Venus a brutal 460° Celsius (860° Fahrenheit).