It may seem impossible that a celestial object as radiant as our sun would be able to hide anything, but images transmitted by NASA's Fermi Gamma-ray Space Telescope have revealed gamma rays from secret solar flares.
Solar flares are super-powered radiation emissions on the sun's surface whose immense electromagnetic energy can sometimes extend far enough to mess with power lines and radio waves all the way on Earth. While none of the flares observed by Fermi were responsible for anyone's radio dying, they were all culprits behind rapid coronal mass ejections that erupted with immense (try a billion tons) solar plasma clouds — and all this chaos was brewing where the spacecraft wasn't supposed to see it.
"Fermi is seeing gamma rays from the side of the sun we're facing, but the emission is produced by streams of particles blasted out of solar flares on the far side of the sun," Stanford University researcher Nicola Omodei explained. "These particles must travel some 300,000 miles within about five minutes of the eruption to produce this light."
The paradox here is that direct light from emissions on the other side should be automatically blocked because the rest of the star blazes in its way. Besides the universe apparently having a sense of humor, these events could illuminate more about how charged particles from solar flares shoot across the sun at the speed of light.
Charged particles accelerated to warp speed are thought to generate radioactive gamma-ray emissions. This is believed to occur because of protons colliding as they strike the solar surface and releasing quickly-decaying subatomic particles, called pions, that degenerate into gamma rays. Astronomers are convinced that particles powered by coronal mass ejections were propelled to the sun’s photosphere (where intense light and heat radiate from), where the proton collisions are thought to have happened, and then its visible face via magnetic field lines that invisibly connect both sides.
NASA's Solar Terrestrial Relations Observatory (STEREO) spacecraft also kept a telescopic eye on the other side of the sun, so it was possible to transmit images of these beyond-the-limb flares (BTL) flares that had never been captured before. The research team is confident that the addition of the STEREO images to what Fermi has already captured will enhance their overall understanding of solar phenomena.
Fermi has been stellar at observing solar flares since 2008, doubling the number of rare beyond-the-limb eruptions it has been able to spot from afar.