Astronomers find a “baby magnetar”

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Astronomers recently observed a new magnetar formed 240 years ago. Measuring around thirty kilometers in diameter, its study will provide a better understanding of the evolution of these extreme objects.

When a massive star comes to the end of its life, for lack of fuel, its outer envelope volatilizes. Her heart then collapses under the effect of gravitation and gives birth to a neutron star. Imagine a small object a few kilometers in diameter with a density of the order of a billion tons, composed almost entirely of neutrons held together by the force of gravity.

Some of these ultra-concentrated star corpses spin very quickly (several hundred times per second). The latter then project very intense beams of radiation into space. From Earth, if we are in the “line of fire”, we have the impression that the neutron star is pulsating. We then speak of pulsar.

Others also have very strong magnetic fields. We then speak of magnetar. It is this object class that interests us here. Indeed, a team of astronomers announces to us today that they have discovered the youngest ever observed.

The object, named Swift J1818.0-1607 and located about 16,000 light years from Earth, was observed when it was only 240 years old (of course, it is much older today). Details of the study are published in The Astrophysical Journal Letters. This “cosmic infant” was spotted last March 12 from NASA’s Neil Gehrels Swift Observatory, betrayed by a sudden explosion of X-rays that made him 10 times brighter than usual.

Physically, the object concentrates about twice the mass of the Sun in a sphere only 30 kilometers in diameter. It also rotates on its axis every 1.36 seconds and has a magnetic field up to 1,000 times stronger than the average neutron star, about 100 million times stronger than the strongest magnet created. by the man. Note that while we have so far identified more than 3,000 neutron stars in the Universe, we have only spotted around 30 magnetars. Being able to observe one at a very early stage is therefore an incredible opportunity since their properties seem to change over time.

Studying the formation of these objects, the researchers point out, may help us understand why there is such a difference between the number of magnetars discovered and the total number of known neutron stars.