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Magnetar flare detected in a galaxy near the Milky Way

  • It is the most distant magnetar confirmed to be detected to date.

  • The M82 star-forming galaxy confirms that magnetars are likely powerful young neutron stars.

  • Researcher Nanda Rea from the ICE-CSIC and IEEC participated in the study published in Nature.

Artistic impression of a magnetar. BCSS/Mt. Visual

Artistic impression of a magnetar. BCSS/Mt. Visual

On 15 November 2023, ESA’s gamma-ray space telescope Integral spotted a sudden explosion from a rare object. For only a tenth of a second, a short burst of energetic gamma-rays appeared from the direction of the bright galaxy M82. The study, in which researcher Nanda Rea from the Institute of Space Sciences (ICE-CSIC) and the Institute of Space Studies of Catalonia (IEEC) participates, is published today in the journal Nature.

The satellite data were received in the Integral Science Data Centre in Geneva (Switzerland), from where a gamma-ray burst alert was sent out to astronomers worldwide, only 13 seconds after its detection. The IBAS (Integral Burst Alert System) software gave an automatic localisation coinciding with the nearby galaxy M82.  

The team requested ESA's XMM-Newton space telescope to perform a follow-up observation of the burst’s location as soon as possible. If this had been a short gamma-ray burst, caused by two colliding neutron stars, the collision would have created gravitational waves and have an afterglow in X-rays and visible light.  

“We immediately realised that this was a special alert. Gamma-ray bursts come from far-away and anywhere in the sky, but this burst came from a bright nearby galaxy,” explains Sandro Mereghetti of the National Institute for Astrophysics (INAF–IASF) in Milan, Italy, and lead author of a paper on this discovery.  

The team used ground-based optical telescopes, including the Italian Telescopio Nazionale Galileo and the French Observatoire de Haute-Provence, to look for a signal in visible light, but they did not find anything. “With no signal in X-rays and visible light, and no gravitational waves measured by detectors on Earth (LIGO/VIRGO/KAGRA), we are certain the signal came from a magnetar,” he concludes.

“The discovery of this magnetar in such a far-away starburst galaxy can help us understanding the reach of the strong magnetic activity in the population young neutron stars as a function of the different host galaxy and environment: something crucial also for other transient events such as Fast Radio Bursts and Gamma-Ray Bursts”, says ICE-CSIC and IEEC researcher Nanda Rea.

Part of the sky measured by the gamma-ray detector on ESA’s Integral satellite. Vague blue blobs dot a dark-blue map of the sky. One blob is much brighter than the others and two images show a cut-out zoom-in on this blob. One of the cut-outs shows X-rays from the galaxy and the other shows an observation in visible light. On both these two cut-out images only the galaxy M82 is seen, and no additional signals from the bright spot. Credit: ESA/Integral, ESA/XMM-Newton, INAF/TNG, M. Rigoselli (INAF).

Part of the sky measured by the gamma-ray detector on ESA’s Integral satellite. Vague blue blobs dot a dark-blue map of the sky. One blob is much brighter than the others and two images show a cut-out zoom-in on this blob. One of the cut-outs shows X-rays from the galaxy and the other shows an observation in visible light. On both these two cut-out images only the galaxy M82 is seen, and no additional signals from the bright spot. Credit: ESA/Integral, ESA/XMM-Newton, INAF/TNG, M. Rigoselli (INAF). 

Magnetars: mega-magnetic dead stars

M82 is a bright galaxy where star-formation takes place. In these regions massive stars are born, live short turbulent lives and leave behind a neutron star. The discovery of a magnetar in this region confirms that magnetars are likely powerful young neutron stars. The search for more magnetars will continue in other star-forming regions, to understand these extraordinary astronomical objects.  

When stars more massive than eight times the Sun die, they explode in a supernova that leaves a black hole or neutron star behind. Neutron stars are very compact stellar remnants with more than the mass of the Sun packed into a sphere the size of a city. They rotate quickly and have strong magnetic fields.   

However, in the past 50 years of gamma-ray observations, only three giant flares have been seen from magnetars in the Milky Way or in a close-by galaxy. These outbursts are very strong: one that was detected in December 2004, came from 30 000 light-years from us but was still powerful enough to affect the upper layers of Earth’s atmosphere. Similar to how Solar flares, coming from much closer to us, influence it.    

“However, outbursts of such short duration can only be captured serendipitously when an observatory is already pointing in the right direction. This makes Integral with its large field of view, more than 3000 times greater than the sky area covered by the Moon, so important for these detections,” emphasises Jan-Uwe Ness, ESA’s Integral Project Scientist.  

More information


A magnetar giant flare in the nearby starburst galaxy M82, Mereghetti et al., Nature. 10.1038/s41586-024-07285-4: https://www.nature.com/articles/s41586-024-07285-4

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Alba Calejero

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ICE-CSIC, IEEC researcher