Twenty years ago today, a small neutron star crossed the Milky Way and shocked the Earth, causing it to ring like a bell. Despite being half a galaxy away, the explosion at the surface of that dead star physically compresses our planet’s magnetic field, overloading some satellites and even destroying Earth’s upper layers. It had the potential to partially ionize the atmosphere. But all of this comes from an object that’s only about 20 kilometers in diameter.
Sometimes scary things come in small packages.
The culprit was magnetar SGR 1806-20, located about 50,000 light years away in the constellation Sagittarius. Magnetars are a special type of neutron star, already at the high end of what the extreme universe can produce. Neutron stars created in supernova flames are formed when the core of a massive star collapses while the rest of the star explodes outward at a significant fraction of the speed of light. The nucleus caves in, its density spikes, and it becomes compressed so much that its electrons are squeezed into neighboring protons (for those who keep track of subatomic particles, antineutrinos are added); Neutrons are formed.
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The resulting neutron-filled object is almost beyond human comprehension. Although they hold more mass than the Sun, they are typically only about 20 kilometers in diameter, making their densities almost comically high. One cubic centimeter of a neutron star is equivalent to about a quarter of the size of a standard six-sided die. will weigh 100 million tons. Imagine crushing every car in America into a mass at once, and then crushing that mass down to the size of a sugar cube. Then you’ll start to get the idea.
The surface gravity of a typical neutron star can be tens or even hundreds of billions of times greater than Earth’s surface gravity. Standing on the surface of a neutron star, a person would weigh billions, or even trillions of tons. But they won’t be able to stand. The immense gravity would flatten them into a vaporized smear of atoms less than a micron high.
Common neutron stars are born with powerful magnetic fields billions of times stronger than Earth’s. However, some can become even more powerful, with magnetic fields a quadrillion times stronger than Earth’s. These are magnetars, one of the most dangerous objects in the galaxy.
Even if you’re just sitting in space doing what you’re supposed to do, magnetars are already super-lethal astrophysical beasts and you don’t want to get caught up in them. However, these objects sometimes flare up, and this term underestimates what is actually happening so much that it is laughable.
A neutron star’s extremely powerful magnetic field is embedded in the object’s crust, and is bound to it like hair growing from your scalp. In some magnetars, the crust can become unstable and eventually slide away. These “starquakes” are very similar to earthquakes, but remember that the Earth’s crust is unimaginably dense and subject to tremendously high gravity. If the Earth’s crust were to crack and shift by a millimeter, the energy released would be cosmically enormous, generating temperatures hot enough to evaporate hundreds of trillions of tons of material on the Earth’s surface. This shakes up the magnetic field so violently that it changes its shape, causing magnetic field lines to break and recombine. Doing this also releases stored energy. The result is a catastrophe of epic proportions.
Magnetars are relatively rare as neutron stars and are sparsely distributed throughout the universe. This usually means that the flare’s impact is attenuated by long distances, so such bursts are usually only detectable by specialized astronomical equipment. However, in rare cases, magnetars may explode. wonderfulflare.
SGR 1806-20 suffered just such an event about 50,000 years ago. It was all over in the blink of an eye. In just a tenth of a second, the Earth’s crust slipped and exploded, knocking out the star’s magnetic field. The fireball is approx. 10 trillion times the total energy output of the sun over the same amount of time. Much of that energy was in the form of ultra-high-energy gamma rays, but it also included X-rays and other forms of light.
To translate this to a global scale, an almost impossible task, this starquake is approximately equivalent to a magnitude 32 earthquake, approximately 32 sextiles stronger than the most powerful earthquake ever recorded on Earth. It was.
That energy rippled throughout the universe for thousands of years, finally reaching Earth on December 27, 2004. The impact was felt immediately.
NASA had just launched the Swift satellite about a month ago. Swift was designed to detect high-energy space explosions from billions of light-years away, but it was unprepared for the explosion of SGR 1806-20. The satellite’s gamma-ray detectors were saturated with energy, even though Swift was not even pointed in the direction of the explosion. The energy penetrated the spaceship’s walls and hit the detector anyway.
Although the initial spike of energy lasted less than a second, Swift’s sophisticated instruments detected a long tail of energy lasting more than five minutes. The brightness of the superflare rose and fell at a very well-defined period of 7.56 seconds, the speed at which the magnetar rotates. As SGR 1806-20 rotated, the turbulent scar where the starquake occurred flashed in and out of our view, causing oscillations of brightness like flashing Christmas lights.
This energy is sufficient to have a physical effect on the Earth, increasing the ionization of the ionosphere (a layer of the Earth’s atmosphere that extends approximately 600 kilometers below the Earth’s surface) and measurably affecting the magnetosphere. Ta. Although the overall impact was small, keep in mind that the magnetar is 50,000 light years from Earth, literally in the middle of the Milky Way from us. If it had been closer, the impact would have been much stronger, akin to a powerful solar flare that could destroy electronic equipment on many satellites and cause chaos on the Earth’s surface.
The good news is that it’s 50,000 light years away. There are some magnetars near us, but we have yet to find one that spews superflares this powerful. The SGR 1806-20 is still at the top of its class in terms of power.
So there’s probably no need to panic or worry about magnetars ruining our day. At the time of the superflare, some pseudoscientific weirdos were speculating that it might have caused the Sumatra-Andaman earthquake and subsequent tsunami, a complete terrestrial disaster that killed nearly a quarter of a million people. I remember. However, that earthquake occurred more than a day later in front When the magnetar explosion hit us, its waves traveled at the speed of light and were about 50 billion kilometers from Earth, still well outside Neptune’s orbit. The two events were not related.
But the explosion of SGR 1806-20 shows how casually the universe wields such unimaginable power. Stars explode, magnetars erupt, and other cosmic events wreak havoc. The good news is that distance makes these giant catastrophes so small that we didn’t even know they existed until relatively recently. Earth has been around for 4.6 billion years, and we’re still here.
If you’re the type of person who counts your blessings at the start of a new year, toast to the sky and be happy that the universe is so vast. Thank you science for helping us observe and understand it.