Normally, after a supernova explosion, a neutron star or a black hole forms. In the past years, however, astronomers have found what seemed to be a third ramification of the violent outburst. It is called a magnetar, an extremely rare form of a neutron star that holds the most powerful magnetic field in the universe, overshadowing even the magnets found on Earth.

A magnetar, like neutron stars, are tiny and extremely dense. They release large amounts of gamma rays when they go through a modification in their crusts known as starquake. How they are formed remains unclear but a team of researchers at the European Southern Observatory (ESO) suggest that magnetars may have originally come from a binary star.

Binary stars are composed of two stars orbiting around a central mass. In the case of magnetars, which are abundant in a star cluster 16,000 light-years away from Earth, scientists deduced that magnetars are originally two stars that orbit so close to each other, the distance is akin to the distance of the orbit of the Earth around the Sun.

This theory came after observing Westerlund 1 in the southern Ara constellation. Dubbed as CXOU J164710.2-455216, it is a recognized home to a dozen of magnetars that bedecks the Milky Way galaxy. After failing to identify the magnetar's pair in the star cluster, scientists then decided to use the Very Large Telescope (VLT) of the observatory to look for evidence in the Westerlund 1.

One distinct characteristic of binary stars is that they have a pair that may have been flung away in such high velocities. They called this runaway stars, and such has been found in a star named Westerlund 1-5.

"In our earlier work we showed that the magnetar in the cluster Westerlund 1 must have been born in the explosive death of a star about 40 times as massive as the Sun. But this presents its own problem, since stars this massive are expected to collapse to form black holes after their deaths, not neutron stars. We did not understand how it could have become a magnetar," said lead author Simon Clark of ESO.

The discovery enabled astronomers to piece details on how the mysterious magnetar came into being.

As per astronomers' observation, when the bigger and more massive star loses its energy, it would transfer its outer layers to the lesser companion that is to become a magnetar. This prompts the magnetar to spin at a rapid rate and this is found to be the root of magnetar's ultra-strong magnetic field. Afterwards, it will grow to be hugely massive it would be losing some of its mass in the process. Some of these would be passed on to what is known today as Westerlund 1-5.

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