On December 27, 2004, the gamma rays of a starquaking magnetar struck the Earth. While that sounds concerning to the less astronomically inclined among us, the fact that you’re here reading about it ten years later should indicate that while fascinating and revelatory about the nature of the universe, it wasn’t all that dangerous. The cascade of gamma rays only temporarily expanded our ionosphere, a mere fraction of the effects that a closer magnetar emission would have on our Earth. To really understand what happened that day and where those rays came from, we have to go back in time, all the way to 1979.
On March 5, 1979, two Soviet probes just past Venus recorded a huge surge in radiation on their sensors. There is always a small amount of background radiation present in the cosmos, heldover from the big bang that created this whole mess, and yet in less than a second both probes detected radiation levels over two thousand times the norm. They weren’t the only man-made objects to pick up the surge. A probe near the sun recorded the wave soon after, as did several satellites in Earth orbit and even observatories on the Earth’s surface. It was, at the time, the largest extra-solar radiation event ever recorded. And because it was observed by so many probes across such a wide distance in our solar system, it was possible to triangulate, using time and distance, the origins of this gamma wave. It was soon discovered that the likely origin point was the site of a known supernova, leading scientists to believe that these gamma rays came from a magnetar.
While they all look similar to the naked eye turned to the sky, there are actually a great many different types of stars. They are vastly different sizes and made of varying materials, and each have unique effects on the universe around them. Magnetars, which are a type of neutron star formed out of the remnants of supernovae, are extremely dense and small, and emit an inordinately strong magnetic field (hence the name). They are so dense that while being just 12 miles across on average (about the length of Manhattan), they have a mass greater than the sun. Were you to scoop up a ladle-full of magnetar material, the contents of your soup spoon would weigh several hundred million tons. And given this extreme density, the magnetic fields around a magnetar are incredibly strong, so strong that before you could even get with 500 miles of the thing to scoop your ladle-full, the electrons in the atoms that comprise your body would be distorted by the magnetism and you would cease to exist. While this is more of a hypothetical effect of the magnetar’s magnetism, there are some very real world effects including the gamma rays that are thrown out across the universe.
The surface of a star is not necessarily a calm place. On neutron stars there are occasionally phenomena known as starquakes, theorized to occur due to the stresses of rapid rotation and intense magnetic fields. As the surface shifts about in these quakes, huge quantities of gamma rays are thrown out into the nothingness of the universe. When they come into contact with other objects, especially ones nearby their originating magnetar, they can be quite destructive. It is estimated that were a magnetar like the one that caused the 2004 gamma ray emission to do so within three lightyears of Earth, our atmosphere would be stripped off completely and the planet wouldn’t be so supportive of organic life anymore. To assuage your fears, the nearest magnetar is over thousands of lightyears away, and their sporadic barrages of gamma radiation serve not as harbingers of doom, but instead as reminders of the many fantastic things out there in this vast universe.