NASA MESSENGER Spacecraft Reveals High-Energy Processes of the Sun from Mercury

Astronomers are learning a bit more about the high-energy processes that occur on the sun. NASA's MESSENGER spacecraft and STEREO measurements have opened up a new way for scientists to understand exactly what's happening within our nearest star.

The MESSENGER spacecraft orbits Mercury, and is as close as 28 million miles to the sun as opposed to Earth's 93 million miles. In fact, the spacecraft is near enough to detect solar neutrons that are created in solar flares, which are powerful bursts of radiation. Solar neutrons only last about 15 minutes, and how far they travel from the sun and into space largely depends on their speed. This means that slower neutrons don't travel fast or far enough to be seen by particle detectors in orbit around Earth.

"To understand the processes on the sun we look at as many different particles coming from the sun as we can-photons, electrons, protons, neutrons, gamma rays-to gather different kinds of information," said David Lawrence, first author of a paper examining these particles, in a news release. "Closer to Earth we can observe charged particles from the sun, but analyzing them can be a challenge as their journey is affected by magnetic fields."

In order to learn a bit more about these particles, the researchers looked at MESSENGER data that corresponded to solar flares that were accompanied by fast-moving energetic charged particles. Then, the scientists used NASA's Solar Terrestrial Relations Observatory (STEREO) spacecraft to examine the flare itself.

In the end, the researchers found that there was an increase in the number of neutrons at Mercury's orbit hours before the large number of particles reached MESSENGER. This showed that the neutrons were most likely produced by accelerated flare particles striking the lower solar atmosphere, releasing neutrons as a result of high-energy collisions.

The findings don't just reveal a bit more about solar processes, though; they also show that MESSENGER in combination with STEREO can provide a clearer and better view of our nearest star.

The latest findings are published in the Journal of Geophysical Research: Space Physics.