Parker Solar Probe's mission to figure out three strange things that the Sun does.
This summer, while you are on the beach soaking up some rays (with your sunscreen on, of course), NASA and the Smithsonian are taking an epic voyage to the Sun. While our closest star gives us fun-filled beach days, it also does some strange things that have puzzled scientists for centuries.
We have always pursued these questions by studying the Sun from a distance, but that is about to change. In August 2018, NASA is launching Parker Solar Probe, a satellite that is headed 96 percent of the way to the Sun. You can get a feel for how close that is in the animation below.
Although we have amazing images of the Sun from afar, we need to get up close to really understand what happens on the Sun and within the solar wind on its journey to the Earth. Parker will measure the characteristics of the plasma (hot gas) and magnetic fields around the Sun to help explain three strange things.
Sitting around the solar campfire
Imagine getting up from a seat near a campfire, walking away from the fire, and getting warmer. This is not something we experience in our everyday life. One of the biggest mysteries in solar physics is just like that weird experience: the temperature of the Sun’s atmosphere, or corona, gets much hotter as you move away from the surface. The Sun’s energy source is its core, where nuclear fusion creates energy. By the time that energy gets to the surface of the Sun, the temperature is about 9,900 degrees Farenheit. But when you measure the atmosphere up above that surface, it is over one million degrees!
So why won’t the Parker Solar Probe burn up when it flies through that hot corona? First, we have a heat shield on the front of the spacecraft that protects the rest of it from the Sun’s direct light, keeping the instruments at around room temperature. Second, the plasma around the Sun isn’t very dense, so there are few particles to contact the spacecraft and transfer their heat. It is much like how you can survive in a sauna temperature well over 100 degrees without being burned, but if you touch a hot stove at around 100 degrees you will.
To solve the campfire mystery, the probe’s SWEAP instrument suite is going to measure the protons, electrons, and helium that make up the solar corona. The SWEAP Solar Probe Cup will poke out from behind the heat shield to literally scoop up these particles. (Since we are traveling all that way, we should get a direct sample from the Sun!) Alongside SWEAP, the FIELDS instruments will measure the magnetic fields in the corona to determine their role in generating the extra heat.
The answer is blowing in the (solar) wind
Eugene Parker, for whom the probe is named (and the only living person to whom NASA has given this honor), theorized in his 1958 paper that the Sun’s heat should cause it to produce an outward stream of particles called “solar wind”. Although his description was not the exact mechanism creating the wind, there is definitely a constant flow of plasma from the solar atmosphere.
Scientists currently study the solar wind when it reaches the Earth, and we see its effect in the form of auroras near the poles. But for the first time, instruments on the probe will measure the speed and the type of particles in the solar wind before it travels to Earth. The WISPR instrument will take images and video of the outflow of this wind as well. With this new information, scientists hope to understand how the solar wind flows outward and where the energy to keep it moving comes from.
Faster than a speeding bullet
Parker Solar Probe will be the fastest human-made object, reaching speeds of over 430,000 mph. But the last phenomena that the probe will study is something even swifter. The fastest particles in the universe move at near the speed of light and travel great distances, cruising through galaxies and solar systems in no time flat. The Sun produces some of these particles through solar flares, as well as the shocks it creates from the solar wind and coronal mass ejections.
The probe’s ISOIS instrument suite will measure these energetic particles and incorporate magnetic field and temperature data. Scientists will use this information to figure out where the energetic particles are being generated and how they propagate through space. Understanding these energetic particles has a direct impact on our lives, because they cause space weather effects that range from endangering astronauts on space walks to impacting the electronics in communication satellites.
As we observe the summer solstice in the Northern Hemisphere, we’re paying extra attention to the Sun. Parker Solar Probe's bold mission to visit and study the Sun is a once in a lifetime event. The spacecraft will launch in early August and make its first close flyby of the Sun in November. Follow the adventure on Twitter @NASASun, @theSWEAPLIFE or at the mission website.