This strange star managed to stop its fall into a black hole
Around a black hole there is sometimes an accretion disk made of swirling and very hot gas, shining in the form of a crown. This is matter that rotates faster and faster as it approaches the black hole and its event horizon, a boundary beyond which nothing can emerge, not even light. Since 2018, a team of astronomers has been monitoring a supermassive black hole at the heart of a galaxy 100 million light years away. And for good reason, it displays particularly abnormal behavior.
The crown of the black hole that played hide and seek in the midst of the Covid-19 pandemic
The black hole 1ES 1927+654 “weighs” 1.4 million solar masses, a heavy weight therefore, but still quite modest. Between 2018 and 2020, the brightness of its crown increased, then decreased by a factor of 10,000, a behavior not at all expected over such a short period. In the midst of the coronavirus, while the world was in lockdown, a team even had the complete surprise of pointing their instrument towards it at the moment when its brightness decreased 100 times in just 8 hours!
Flashes every 7 minutes caused by an object at 150,000 km/s
Another team of NASA astronomers (Goddart Space Flight Center in Greenbelt) also took the black hole as a target to try to understand this unprecedented phenomenon. They noted new X-ray flashes, and this is where it gets exciting. Indeed, these increased continuously with an orbital period increasing from 18 min to 7 min! Scientists have deduced that if they are caused by an object orbiting in the corona, then that thing is going at half the speed of light. However, nothing like this had ever been observed so close to a black hole…
“One way to produce these oscillations is with an object orbiting inside the black hole's accretion disk. In this scenario, each increase and decrease in X-ray intensity represents an orbital cycle”explains Megan Masterson, co-author of the study.
Therefore, if this orbital period decreases, this means that the object – at this stage of our article unidentified – is approaching the black hole, in particular by having its energy drained by the generation of gravitational waves.. Until to logically end up sinking into the horizon of the black hole? Well… no: amazed astronomers observed that the period ended up stabilizing.
We were shocked to see the object begin to slow down
“We were shockedadmits Masterson, but we understood that by getting closer to the black hole, the object could be torn from the matter. This loss of mass could stop the inward movement of the companion.”
But what could this object be, whose unenviable fate is to revolve around its own death? Astronomers today are leaning towards a dying star, a white dwarf with around 10% of the mass of the Sun, but only having the volume of the Earth. Indeed, the extraordinary density of these dying stars would allow them to partially resist the damage of gravitational attraction (the tidal forces) which operate so close to the horizon of a black hole.
