MASSIVE EXPLOSION SPOTTED ON MYSTERIOUS DEAD STAR
A satellite in the right place at the right time captured an important cosmic sight
With so many wonders spread out in space, it’s daunting to think how much is happening when no one is looking. That’s why astronomers were thrilled when a satellite happened to be looking in just the right direction as a rare explosion in space occurred.
The giant eruption lit up a whole galaxy, known as M82, 12 million light-years away from Earth. Thinking two colliding neutron stars caused the explosion, astronomers searched for an afterglow, but there wasn’t one. They realised this intense gamma-ray burst must have come from a single, megapowerful neutron star. Neutron stars are the remains of massive stars, eight times larger than our Sun, after they explode in a supernova. Instead of turning into a black hole, the remains form compact spheres with strong magnetic fields.
But the observed neutron star’s magnetic fields were superstrong, making it a magnetar, an extremely magnetic neutron star. With magnetic fields over 10,000 times stronger than average neutron stars, magnetars have the strongest magnetic fields measured in the Universe and emit energy through giant flares. It was one of these flares that ESA’s satellite INTEGRAL happened to capture last November. The burst only lasted one-tenth of a second, but within 13 seconds a gamma-ray burst alert was sent to astronomers worldwide.
“We immediately realised that this was a special alert. Gammaray bursts come from far away and anywhere in the sky, but this burst came from a bright, nearby galaxy,” said Dr Sandro Mereghetti of the National Institute for Astrophysics, Italy, lead author of the study published in the journal Nature.
Mereghetti’s team took ground- and space-based telescope observations straightaway, but they didn’t pick up any signals of visible light, X-rays, or gravitational waves. INTEGRAL had captured a unique and transient moment that left no traces.
Without these traces, the most likely answer behind the explosion is the mega-magnetic neutron explanation – making this the first confirmed magnetar flare outside the Milky Way. In the past 50 years, scientists have identified only three giant flares as originating from a magnetar in our galaxy.