NASA Captures Images of Sun’s Edges, Reveals Origin of Solar Winds

New observations from NASA's Solar Terrestrial Relations Observatory (STEREO) reveal how solar winds evolved.

NASA's STEREO-A and STEREO-B twin spacecraft have been tasked to study the sun's edges to find out how the solar winds -- the constant flow of charged particles in the sun -- have formed. The discovery will help scientists know more about the solar materials in the space environment to safely explore beyond Earth. NASA released a video showing how the charged particles transition from the sun's outer atmosphere to solar winds.

"Now we have a global picture of solar wind evolution," Nicholeen Viall, a solar scientist at NASA's Goddard Space Flight Center and co-author of the study, said in a statement. "This is really going to change our understanding of how the space environment develops."

Scientists have discovered solar winds during the 1950s, but its origin had been difficult to pin down. The space environment in the solar system is dominated by the activity on the sun. According to scientists, the sun and its atmosphere are made of plasma, which is a mix of positively and negatively charged particles that have separated at extremely high temperatures, that carries and travels along magnetic field lines.

These particles steam out from the sun's corona or outer atmosphere and fill the solar system, spreading beyond Pluto. The new observations from NASA's STEREO instrument have shown that the plasma undergoes changes as it travels further away from the sun.

"As you go farther from the sun, the magnetic field strength drops faster than the pressure of the material does," Craig DeForest, solar physicist at the Southwest Research Institute and lead author of the study, said in the same statement. "Eventually, the material starts to act more like a gas, and less like a magnetically structured plasma."

Prior to the study, scientists have already hypothesized that magnetic forces had an important role in shaping the corona. But it was only through the current observation that they were able to see it. The effect is difficult to capture on camera because the plasma is tenuous and contains electrons that scatter sunlight.

To see the effect, scientists separated the faint features of the solar wind from the background noise and light sources over 100 times brighter than the plasma itself. These light sources include the background stars, stray light from the sun, and dust in the inner solar system.

According to NASA, the new analysis will help scientists understand the observations of NASA's Solar Probe Plus mission, which is scheduled to launch in 2018 and fly into the sun's corona.