Astronomers have made an exciting discovery that could change how we understand some of the most powerful explosions in the universe.
Using data from NASA’s Fermi Gamma-ray Space Telescope, scientists found strong evidence that a rare type of exploding star, called a superluminous supernova, may be powered by an extremely magnetic neutron star known as a magnetar.
The findings were published in the journal Astronomy & Astrophysics and mark the first convincing detection of gamma rays from this kind of supernova.
Most supernovae happen when a massive star runs out of fuel.
Without enough energy to support itself, the star collapses under its own gravity and then explodes.
Sometimes the collapse leaves behind a neutron star, which is an incredibly dense object about the size of a city. In other cases, a black hole forms.
But superluminous supernovae are far brighter than normal ones. They can produce more than 10 times the visible light of a typical stellar explosion, and scientists have long wondered what gives them this extra energy.
The newly studied explosion, called SN 2017egm, happened in the galaxy NGC 3191, about 440 million light-years from Earth in the constellation Ursa Major. Even though it was extremely far away, it is still one of the closest superluminous supernovae ever observed.
Researchers examined 16 years of Fermi telescope data and searched for gamma rays from the six nearest superluminous supernovae. Only SN 2017egm showed clear evidence of gamma rays.
Gamma rays are the most energetic form of light in the universe. Detecting them from a supernova gives scientists a new way to look deep inside these cosmic explosions.
The team believes the explosion was powered by a newborn magnetar spinning hundreds of times every second. Magnetars have the strongest magnetic fields known in the universe — trillions of times stronger than ordinary refrigerator magnets.
As the magnetar spins, it releases huge amounts of energy and creates a cloud filled with energetic particles. Inside this cloud, particles and light constantly collide, producing gamma rays.
At first, these gamma rays become trapped inside the expanding debris from the explosion. But after several months, as the debris spreads out and cools, some of the gamma rays can finally escape into space.
The researchers say their magnetar model matches both the brightness of the supernova and the timing of the gamma rays detected by Fermi. However, they believe other processes may also help explain the explosion’s strange fading pattern over time.
Scientists hope future observatories, including the Cerenkov Telescope Array Observatory, will help detect more events like SN 2017egm. These discoveries could offer a deeper understanding of how stars die and how some of the universe’s most extreme objects are born.
