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Using the European Southern Observatory’s (ESO’s) Very Large Telescope, European astronomers have for the first time demonstrated that a magnetar — an unusual type of neutron star with an incredibly strong magnetic field — was formed from a star with at least 40 times as much mass as the Sun. This challenges the understanding of current theories on how stars evolve, as a star as massive as this was expected to become a black hole, not a magnetar.

To reach their conclusions, the astronomers looked in detail at the extraordinary star cluster Westerlund 1, located 16 000 light-years away in the southern constellation of Ara (the Altar). The astronomers used the FLAMES instrument on ESO’s Very Large Telescope at Paranal, Chile to study the stars in the Westerlund 1 cluster.

The previous assumption was that stars with initial masses between of about 10 and 25 solar masses would form neutron stars and those above 25 solar masses would produce black holes. “This therefore raises the thorny question of just how massive a star has to be to collapse to form a black hole if stars over 40 times as heavy as our Sun cannot manage this feat,” concludes co-author Norbert Langer. To read the full story online, visit the ESO website.

To find out more about black holes, why not have a look at the ‘Black Hole Mathematics’ resource produced by NASA which you can download from the National STEM Centre eLibrary.