Magnetar Burst from Nearby Galaxy M82: ESA’s Groundbreaking Discovery

A strange signal from a nearby galaxy

In November 2023, the ESA Comprehensive Space Observatory he discovered a sudden explosion, only a tenth of a second old. The data was obtained at Integrated Science Data Center in Geneva, which itself sent a gamma-ray burst warning to astronomers around the world, just 13 seconds after the discovery. IBSA (Integral Burst Alert System) software provided simultaneous location the nearby galaxy M82.

It was now up to astronomers to find out what happened: Was it a common gamma-ray burst or an unusual large magnetar burst?

“We immediately realized this was a special warning. Gamma-ray bursts come from distant places and anywhere in the sky, but this burst came from bright astronomy nearby,” explained Sandro Mereghetti from the National Institute of Astrophysics (Sandro Mereghetti).INAF-IASF) in Milan, Italy, and lead author of a study about this discovery published in the journal Nature.

The team asked ESA’s XMM-Newton space telescope to follow up on the location of the explosion as soon as possible. If this had been a a brief gamma-ray burst caused by the collision of two neutron starsthe accident would have been created gravitational waves and there would be an afterglow in X-rays and visible light.

“The XMM-Newton observations only showed the hot gas and stars in the galaxy. If this burst had been a short burst of gamma rays, we would have seen a faint source of X-rays coming from the site, but this evil was not present,” said study co-author Michela Rigoselli of INAF-IASF.

Astronomers then used ground-based optical telescopes, including the Italian Telescopio Nazionale Galileo and the French Observatoire de Haute-Provence to detect a signal in visible light hours after the explosion.

“But again we found nothing. With no signal from X-rays and visible light and no gravitational waves measured by Earth detectors (LIGO/VIRGO/KAGRA), we are sure the signal came from a magnetar” , concluded Sandro Mereghetti.

Magnetars: megamagnetic, recently dead stars

When stars with a mass greater than eight times that of the Sun die, they explode in a supernova which causes a black hole or neutron star.

As neutron stars They are very complex stellar remnants, with more mass than the Sun, compressed into a sphere the size of a city. They rotate quickly and have strong magnetic fields.

“Some young neutron stars have extra strong magnetic fields, more than 10,000 times stronger than normal neutron stars – they are called magnetars. They release energy in explosions and, from time to time, these explosions are terrible”, explained Ashley Chrimes, ESA researcher.

However, in the last 50 years of gamma-ray observation, only three large magnetar explosions in our galaxy. What was it was discovered in December 2004, coming from 30,000 light years awayso powerful that it affected the upper layers of the Earth’s atmosphere in the same way that they affect solar flares, which come from much closer.

“First proof of a magnetar outside the Milky Way”

This burst was recently discovered by ESA’s Integral “It is the first confirmation of a magnetar outside the Milky Way. We suspect that some of the other ‘brief gamma-ray bursts’ that Integral and other satellites have detected are also large magnetar bursts.”said Sandro Mereghetti.

“This discovery extends our search for other extragalactic magnetars.” If we can find more, we can begin to understand how often these explosions occur and how these stars lose energy in the process,” said Ashley Chrimes.

Jan-Uwe Ness, ESA Integral Project Scientist, explain what “Such short bursts can only be caught by accident when an observatory is already pointing in the right direction. That’s why Integraç is so important, because it has a wide view, more than 3,000 times greater than the area of ​​the sky covered by the Moon.

M82 is a bright galaxy where massive stars are born, live short, turbulent lives and, when they die, produce neutron stars. The discovery of a magnetar in this region confirms that the magnetars are likely to be young neutron stars.