In the expanse of space, where stars burn and galaxies collide, there exists a type of star so strange and powerful that it challenges our understanding of the universe. These are called magnetars. They are the strongest magnets known to exist, with magnetic fields trillions of times stronger than Earth’s. To understand magnetars, we first need to take a closer look at how stars live and die.
A star like our sun is essentially a gigantic ball of gas, mostly hydrogen, that burns through nuclear fusion. This fusion process generates energy, which balances out the force of gravity pulling inward. Over time the fuel for fusion runs out, and the star collapses under its gravity. Depending on the size of the star, this collapse can lead to different outcomes. A star like our sun will eventually become a white dwarf, but larger stars undergo a more violent fate.
When a massive star, at least eight to 10 times the size of the sun, runs out of fuel, it ends its life in a supernova explosion. The core that remains can collapse into an incredibly dense object called a neutron star, which is the core of the star compressed into an area the size of a city. A neutron star packs a mass greater than the sun into a space only about 12 miles across, resulting in extreme gravitational forces.
Magnetars are a special type of neutron star. What sets them apart is their extraordinarily powerful magnetic fields, which can be over 1,000 times stronger than that of a regular neutron star. To put this in perspective, the magnetic field of a magnetar can reach up to 10^15 gauss (that is, a “1” followed by 15 zeros).
For comparison, Earth’s magnetic field is around 0.5 gauss, and the strongest magnets humans can create in laboratories measure around 100,000 gauss. In other words, magnetars are nature’s ultimate magnets, and they dwarf anything we could hope to build.
The origin of these powerful magnetic fields is still not entirely understood, but scientists think it may be due to a phenomenon called the “dynamo effect.” As the neutron star forms, it spins very rapidly, and this rapid rotation, combined with the star’s extreme density, might generate the super-strong magnetic fields we observe. However, magnetars also lose their energy more quickly than regular neutron stars, and they slow down as their magnetic fields weaken over time.
Magnetars can produce some of the most energetic bursts of radiation in the universe. These bursts come in the form of X-rays and gamma rays and can release more energy in a fraction of a second than the sun produces in 100,000 years. The most powerful of these bursts is called a “giant flare,” which can briefly outshine all the stars in its galaxy.
While magnetars are fascinating, they are also rare. There are thought to be only around 30 known magnetars in our galaxy, the Milky Way, compared with the hundreds of thousands of regular neutron stars. Fortunately for us, the closest magnetar is about 9,000 light-years away, so there’s no danger of its intense radiation or magnetic forces affecting Earth.
Despite their small size, magnetars possess incredible energy and provide scientists with an opportunity to study the fundamental laws of physics in one of the most extreme environments known. They are a crucial piece in understanding the life cycles of stars and the mysteries of cosmic magnetism.
Richard Brill is a retired professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.
