A Dormant Extragalactic Black Hole

Welcome to this week’s AITN Lite! As usual, I have tried to find a link between the full bulletin last week. The bulletin was about the jets launched from the central black hole in galaxies, and this week’s is about black holes, just not those in the centre of galaxies. To be specific, it is about the first dormant black hole unambiguously discovered in an extragalactic system. The article can be found here:


Massive stars preferentially form in binary or multiple systems. Stars with an initial mass between 8 and 16 solar masses have a multiplicity fraction of greater than 60%, which rises to 80% for masses more than 16. These massive stars end their lives in core-collapse supernovae. Stars that are initially more massive than 40 solar masses leave behind a black hole, and some even collapse straight into a black hole. However, when two massive stars are in a binary system, and one has exploded via supernova, you end up with a black hole orbiting a massive star.

In this system, VFTS 243, a 9 solar mass black hole is found orbiting a 25 solar mass star. VFTS243’s black hole was difficult to discover though since it is considered dormant. It is dormant as it does not have significant levels of x-ray emission, the usual method for detecting a black hole, which is emitted due to material accreting into it. A long observing program of the kinematics of the star left the authors with no other plausible scenario that there was a companion black hole.

Curriculum topics to be considered
Stellar life cycle

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