An impressive explosion led astronomers to the discovery of the first magnetic star outside the Milky Way – and suggests the possibility of the existence of many others in the immensity of the Universe.
This newly identified magnetar, a compact remnant of a dead star, is endowed with an exceptionally powerful magnetic field. It resides in the galaxy Messier 82 (M82), also known as the “Cigar Galaxy”, located about 12 million light years from Earth.
The detection of this ultramagnetic body occurred when it violently erupted, emitting intense energy that persisted for a fraction of a second, as detailed in a new study published in the journal Nature this Wednesday (24).
Magnetars: most powerful magnets in the cosmos
Referred to by some as the most powerful magnets in the cosmos, magnetars are highly magnetized, rotating variants of neutron stars – supernova remnants – that shine thousands of times more brightly than the Sun.
However, its eruptions are so brief and unpredictable that they represent challenging targets for astrophysicists to study. Only three other magnetar explosions have been documented in the last 50 years (all in the Milky Way), so scientists say this discovery opens up new perspectives in the search for these magnetic stars in other galaxies.
“The identification of a greater number of these celestial bodies could provide insights into the frequency of these explosions and the process of energy dissipation from these stars”, commented Ashley Chrimes, a researcher at the European Space Agency (ESA), who was not directly involved in the study, in press release.
Read more:
Magnetic star was discovered by European space telescope
In mid-November 2023, ESA’s Integral Space Telescope detected a brief, sudden burst of gamma rays toward the galaxy M82. This type of radiation is also generated during the formation of black holes, mergers of orbiting neutron stars, and other exotic phenomena unrelated to magnetars.
“We knew immediately that this was an extraordinary event,” said Sandro Mereghetti, a researcher at the National Institute of Astrophysics in Italy and lead author of the new study. “Gamma ray bursts can occur from many sources in the Universe, but this one in particular emanated from a nearby, bright galaxy.”
Subsequent observations of the explosion, carried out hours later with ground and space telescopes, were able to locate its origin within the “Cigar Galaxy”. Unlike the expected afterglow and gravitational waves associated with a conventional gamma-ray burst, astronomers only identified hot gas and stars, thus confirming that the emission came from a magnetar.
Called a “stellar earthquake”, the phenomenon occurs when the intense magnetic fields of a magnetar cause a slight distortion in its rotation, disrupting its outer layers and releasing highly energetic gamma rays into the cosmos, astronomers explain.
