Why Are Magnetars So Scary?

Stars go through a life cycle like everything else in the universe. What happens to a star at the end of its life depends on the mass of the star. For example, our sun is expected to grow into a red giant, then become a planetary nebula, then turn into a white dwarf star. More massive stars can explode into supergiants, erupt into supernovae, and then become either a neutron star or a black hole.

Magnetars are the remnants of those massive stars which have exploded in a supernova and collapsed into a neutron star. While astronomers don't yet know what causes a supernova to result in a magnetar instead of a "normal" neutron star or pulsar, some hypothesize that it has to do with the original star's rotational speed.

Magnetars are neutron stars with fields of approximately 1013 to 1015 Gauss (a measure of magnetic density). This is a scale of magnetic power that's hard to conceive, but let's just say that magnetars are considered to be the most powerful magnetic objects in the known universe.

Scientists have confirmed the presence of 23 known magnetars, and another six are waiting additional data to confirm if they meet the criteria to be considered magnetars. Many of these are located in the Milky Way, but don't worry: None are close to Earth!

Some of the magnetars near Earth include AXP 1E 1048-59, which is located about 9,000 light-years away in the constellation Carina; SGR 1900+14, 20,000 light-years away in Aquilla; SGR 1806−20, 50,000 light-years away in Sagittarius; and SGR 0525−66, 165,000 light-years away in the Large Magellanic Cloud (just outside the Milky Way). These distances are obviously far beyond anywhere we've explored in our galaxy – or even sent probes like Voyager 1 or 2 to visit.

Black holes definitely get a lot of headlines – and they're certainly not the kind of thing we'd want close to Earth. But are they more powerful than magnetars, which are the most powerful magnets in the universe? Phil Plait, an astonomer who shares his insights under the moniker Bad Astronomer, says in an email that it depends on what force you're measuring.

"The gravity from the black hole will always be stronger, because the lowest mass black hole is always more massive than the most massive neutron star," Plait says. "[But] the magnetism of the magnetar will be stronger, in general."

Luckily, we'll never have to worry about encountering a black hole or a magnetar close to Earth, but both could theoretically impact us here on Earth. "If a stellar mass black hole eats something it could blast out radiation, but even then I doubt it would be as strongly felt from halfway across the galaxy as the 2004 magnetar event," says Plait, referring to the massive gamma and X-ray blast that passed over Earth that year and caused disruptions to satellite technology, among other issues.

So, while a magnetar might not win in a cosmic "battle" against a black hole, they're powerful enough to affect us here, and that's worth paying attention to when you see one mentioned in the news.

If you ask an astronomer, many will say that magnetars are among the scariest objects in the galaxy. Certainly you don't want to be near one – but the massive blasts of energy they produce can impact us here on Earth despite their great distance away. "I am worried about magnetars, given what happened in 2004," says Plait. "[SGR 1806-20] is exceptionally powerful. I don't think any that strong are closer [to Earth], but the impact on Earth gets stronger with the inverse of the distance squared. If one were one-fifth that distance the impact would be 25 times stronger."

As astronomer Paul Sutter points out in his 2015 article in Space.com titled "Why Magnetars Should Freak You Out," not only would a strong magnetar pulse affect our electronics and technology, but one with enough strength would affect our physiology, including the bioelectricity in our bodies — and between the atoms that make up everything we know. Let's just say we should all be glad that the nearest known magnetar is 9,000 light-years away.