Des chercheurs du Massachusetts Institute of Technology (MIT, États-Unis) pensent avoir mis la main sur une « veuve noire » des plus étonnante. Un système formé d’un pulsar – ici pour illustration, le pulsar du Crabe – et de non pas une, mais deux étoiles compagnes. © Nasa, CXC, SAO, F. D. Seward, W. H. Tucker, R. A. Fesen

Quelle est cette « veuve noire » dans notre ciel ?

If I tell you black widow, you necessarily think of this spider with disastrous habits. But know that the little beast is not the only one to deserve this nickname. Some “black widows” are also hiding in our sky. Astronomers also think they have unmasked a new one, with somewhat surprising behavior.

The Black Widowfor biologists, it is a spider a little special. ‘Cause she can release a venom mortal for men, first. But also because the black widow females have a habit of devouring the males, smaller than them, after thecoupling. And it is this funny characteristic that is also worth their nickname to some binary systems ofstars. Systems consisting of a pulsar – the collapsed remains of a massive star, a neutron star in very rapid rotation on itself – which, for gravity, gradually devours a smaller companion star. Earning an additional duration of life.

From astronomers of Massachusetts Institute of Technology (MIT, USA) have just observed what looks like a new one of these “black widows”. At 3,000 light years of our Earth approximately. A surprising system in more than one respect. First because the one to be called ZTF J1406+1222 was detected in visible light. Signaling itself to researchers by the characteristic and spectacular blinking of the pulsar’s companion star. Classically, it is rather the gamma and X rays emitted by the pulsar that alert astronomers.

Another peculiarity of ZTF J1406 + 1222 revealed by a brightness varying by a factor of 13: sa orbital period extremely short. The shortest ever observed elsewhere. With a pulsar and a star that revolve around each other in just… 62 minutes!

A ” Black Widow “ or maybe something else

And ZTF J1406+1222 doesn’t stop there. This funny ” Black Widow “ seems to be keeping a third star under its wing. More distant. Which completes its lap in 10,000 years. A configuration that raises questions for astronomers.

To explain it, they consider that, as is the case with most “black widows” known – about two dozen so far – this triple system was formed in a globular cluster. Long before our Sun starts to shine. Drifting towards the center of the Milky Waythe latter could have been disturbed by the gravity exerted by the supermassive black hole who lives there. Disturbed enough to burst while leaving ZTF J1406+1222 intact.

But astronomers at MIT are warning us. While waiting for new observations, it remains more prudent to continue to consider this triple system as a candidate ” Black Widow “. After all, he hasn’t (yet) revealed anyemissions gamma or X-rays characteristics of the presence of a pulsar. The only thing the researchers are certain of is that they have detected a star with one side much hotter than the other – the one that potentially receives the constant radiation from the pulsar – and which is orbiting around something in a little over an hour. So, if everything indicates that it is indeed the companion of a pulsar and a ” Black Widow “it could also be something… entirely new!

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