Scientists have detected a dramatic excess of gamma rays pouring out from the Sun, which represent the highest-energy light emissions ever detected from Earth’s star.
“The sun is more surprising than we knew,” said postdoctoral research associate Mehr Un Nisa of Michigan State University, who worked on the new study published in the journal Physical Review Letters. “We thought we had this star figured out, but that’s not the case.”
The unexpected discovery was made by scientists sifting through six years of observations captured by the High-Altitude Water Cherenkov Observatory, also known as HAWC, which has been vigilantly tracking gamma ray emissions ever since it was completed in March 2015.
HAWC’s data revealed that our Sun is capable of creating a dramatic excess of super energetic gamma rays that extends beyond what current models of our Sun’s behaviour can explain. For context, visible light emitted by our Sun as a result of the nuclear fusion reaction raging at its heart carries energy the equivalent to one electron volt.
However, the gamma rays detected by HAWC registered as carrying anywhere from one trillion, up to almost 10 trillion electron vaults. According to the release from Michigan State University, that makes the gamma rays "the highest-energy light ever observed from the sun".
“After looking at six years’ worth of data, out popped this excess of gamma rays,” explained Nisa. “When we first saw it, we were like, ‘We definitely messed this up. The sun cannot be this bright at these energies.’ ”
A significant amount of the gamma rays produced by the Sun are created when our star’s atmosphere is struck by charged particles known as cosmic rays. These high energy particles are themselves created during cataclysmic events that take place far beyond the borders of our solar system, such as the death of a star in a dramatic supernova, or as a byproduct of a feasting black hole.
Upon being deflected back outwards into space by the Sun’s magnetic field, cosmic rays interact with gasses in the stellar atmosphere, triggering the creation of solar gamma rays, some of which are absorbed by Earth’s dense atmosphere.
Back in 2011 NASA’s Fermi telescope revealed the Sun was capable of producing extremely energetic gamma rays, and that the star was creating roughly seven times the number of them than had been expected based on earlier estimations. However, according to the Michigan State University, the Fermi telescope's detections were limited by the capabilities of its gamma ray detector, which could only track particles with energies up to 200 billion electron volts.
HAWC, however, has no such limitations, and is capable of detecting gamma rays carrying the energy of trillions of electron volts. Located 13,000 feet above sea level, nestled between the peaks of two sleeping volcanoes near Puebla, Mexico, HAWC Is about as far from a conventional telescope, aesthetically speaking, as you can possibly get.
It doesn’t have the cylindrical design of the venerable Hubble Space Telescope, nor does it boast the golden mirrors and reflectors of NASA’s origami-like James Webb Space Telescope. Instead, HAWC Is made up of a collection of 300 water tanks filled with roughly 60,000 metric tons of purified water.
When gamma rays strike Earth’s atmosphere they break down into fragments of light and lower energy particles known collectively as ‘air showers’. Upon coming into contact with the water tanks, the particles create light in the form of Cherenkov radiation, which is then detected by HAWC’s instruments.
Alongside gathering readings as to the incredibly energetic nature of the gamma rays, the HAWC data also revealed that they had a tendency to occur when the Sun is experiencing a relatively dormant phase of its 11-year activity cycle. Moving forward, scientists will be looking to address the question as to how the Sun's magnetic field shapes interactions with the cosmic rays, giving rise to the high energy gamma rays.
“This shows that HAWC is adding to our knowledge of our galaxy at the highest energies, and it’s opening up questions about our very own sun,” said Nisa, one of almost 100 scientists who contributed to the paper. “It’s making us see things in a different light. Literally.”
Image Credit: NASA/SDO
Anthony is a freelance contributor covering science and video gaming news for IGN. He has over eight years experience of covering breaking developments in multiple scientific fields and absolutely no time for your shenanigans. Follow him on Twitter @BeardConGamer
