Strange X-ray pulses blasted out from a recently awakened monster black hole are the most powerful astronomers have seen, and may help explain how these cosmic behemoths emerge from their slumber.
A few years ago, astronomers spotted mysterious rhythmic signals coming from a black hole. The exact cause was unclear, but because the signals appeared to have repeating elements, they were dubbed quasi periodic eruptions (QPEs). Since then, astronomers have discovered a handful of QPEs coming from other black holes, but they are so rare that it is difficult to form a complete picture of what may be causing them.
One possible explanation for these events, which can appear brighter than the light from all the stars in a galaxy combined, is that they happen when an orbiting star is sucked into the accretion disc of a black hole, the ring of ultra hot gas and dust surrounding it.
Advertisement
Now, at the University of Valpara铆so in Chile and her colleagues have spotted the most extreme QPEs from a black hole seen so far, which might suggest an entirely new mechanism is producing them. While previous QPEs took place over a matter of hours, this one is far slower, with eruption cycles lasting for multiple days. 鈥淚t鈥檚 much longer, and at least 10 times more energetic than any other QPE known before,鈥� says Hern谩ndez Garc铆a.
The black hole鈥檚 home, at the centre of a galaxy called SDSS1335+0728, grabbed the interest of astronomers in 2019 when it suddenly brightened after decades of inactivity. Last year, Hern谩ndez Garc铆a and her team were looking at the galaxy using an X-ray telescope when they noticed that it was also sending out strange, periodic signals, lasting for days at a time. 鈥淚t was crazy, we weren鈥檛 expecting that,鈥� says Hern谩ndez Garc铆a.
The length of the QPEs suggest that, rather than a star being sucked into an accretion disc, the signal could be related to the process of the black hole switching on after lying dormant as it begins to accrete material around it, says Hern谩ndez Garc铆a, though this process is still mysterious.
While these QPEs are more extreme, the relationship between the length of time between the flares and how long they last appears to be the same ratio as previous QPEs, which suggests that there may be a shared underlying physics to all QPEs related to the accretion disk, says at Queen鈥檚 University Belfast.
Nature Astronomy
Spend a weekend with some of the brightest minds in science, as you explore the mysteries of the universe in an exciting programme that includes an excursion to see the iconic Lovell Telescope.
Mysteries of the universe: Cheshire, England
