Like an immense donut (or toroid) that expands daily. That’s how Jesús Corral-Santana, a researcher at the Instituto de Astrofísica de Canarias (IAC), describes the odd – hitherto unknown – structure of the binary system Swift J1357.2-0933, consisting of a ‘normal’ star and a stellar-mass black hole (which feeds off its companion star). The research, which Corral is first author and is published in the latest issue of Science, follows the stages of the outburst of the system, an event that occurs only once in decades or centuries.
The team observed strange eclipses in the system that lasted and were repeated every few minutes. This finding led them to two conclusions: they had to be viewing the black hole edge on (it had an inclination of at least 75 degrees) and it presented an odd vertical structure within the accretion disc of the system. In other words, the matter being drawn from the companion star formed an outflow in the shape of a whirlpool, rather like water flowing down a plughole.
The team observed strange eclipses in the system that lasted and were repeated every few minutes. This finding led them to two conclusions: they had to be viewing the black hole edge on (it had an inclination of at least 75 degrees) and it presented an odd vertical structure within the accretion disc of the system. In other words, the matter being drawn from the companion star formed an outflow in the shape of a whirlpool, rather like water flowing down a plughole.
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