TAU deciphers why a black hole randomly ceased swallowing material
TAU chalks up the possibility that a star "got too close to the dining table," causing the disruption - being devoured in the process.
By JERUSALEM POST STAFFA supermassive black hole with millions to billions times the mass of our sun is seen in an undated NASA artist's concept illustration.(photo credit: REUTERS/NASA/JPL-CALTECH/HANDOUT)
In a galaxy far, far away, 300 million light years to be exact, a "super-massive" black hole has Tel Aviv University scratching its head - it just randomly stopped its process of swallowing material out of the blue.TAU chalks up the possibility that a star "got too close to the dining table," causing the disruption - although devoured by the black hole in the process.“We’ve never seen a black hole behave this way”, said research co-lead Dr. Benny Trakhtenbrot. “Usually, the amount of radiation from the vicinity of a black hole is directly linked to the rate at which it accretes material. So the sharp rise in the visible radiation was telling us that the accretion rate is increasing, while the decrease in X-ray radiation was telling us that the accretion rate is actually decreasing."Black holes can contain a mass that ranges from being the equivalent of a large mountain up to that of thousands or even millions times greater than the sun. “Supermassive” black holes, for example, have a mass greater than 1 million suns combined. . The reason remains unclear just how such high masses are reached, despite how commonplace they are.Although some may swallow gas in their surroundings and others may suddenly swallow whole stars, no theory explains how they can "switch on" (or off in this case) unexpectedly.“It was so strange that, at first, we thought maybe there was something wrong with the data”, said assistant professor at Diego Portales University in Santiago, Chile Dr. Claudio Ricci.Co-lead author Dr. Iair Arcavi added, "We’ve seen several cases of black holes tear apart stars that got too close, but until now we’ve never seen it happen around a black hole with a pre-existing disk of material, nor the collision that ensues.”A study led by Trakhtenbrot and Arcavi two years ago revealed how some supermassive black holes are triggered to grow.In February 2017, the All Sky Automated Survey for Supernovae (ASAS-SN) discovered an event known as AT 2017bgt. This event was initially believed to be a "star swallowing" event, or a "tidal disruption" event, because the radiation emitted around the black hole grew more than 50 times brighter than what had been observed in 2004.After extensive observations using a multitude of telescopes, concluded that AT 2017bgt represented a new way of "feeding" black holes.
"The ASAS-SN sky survey measured a 50-fold increase in the visible radiation emitted around the black hole, and observations taken by the researchers using the Las Cumbres network of robotic telescopes showed rapid changes in the form and source of the radiation," TAU said. "A few weeks later, the team pointed NASA’s Swift, NuSTAR and NICER space telescopes, as well as the European Space Agency’s XMM-Newton space telescope at the black hole, and noticed a 10,000-fold decrease in the X-ray radiation coming from the black hole’s vicinity.""We quickly realized that this time, there was something unusual," said Trakhtenbrot. "The first clue was an additional component of light, which had never been seen in tidal disruption events."However, the same black hole seems to have gone in the opposite direction - although a wandering star seems to be the prime suspect, the authors state that there could be other explanations for the unprecendented observation."Day to day, the NICER telescope, installed on the International Space Station, detected dramatic variation, sometimes changing in brightness by a factor of 100 in a few hours. such rapid changes occurring continuously for months, have never been seen before," TAU explained in a press release.Black holes have fascinated science lovers and the wide public alike since the first modern solution for characterizing them in 1916 by the German physicist Karl Schwarzschild.As with many topics within the field of Quantum Physics, black holes mesmerize scientists with their mysterious characteristics that physicists are still trying to predict and understand.But what are we talking about when we talk about black holes?First things first: a black hole is anything but an empty space. Quite the opposite - it’s composed of an enormous amount of matter produced from the collision of stars, later compressed into a small space. The matter is condensed to such an extent that the pulling force of gravity becomes so strong that even light cannot escape it - hence the name black hole, due to its invisibility.Albert Einstein’s Theory of General Relatively predicts that sufficiently compacted mass can deform space-time - which is an accurate characterization of a black hole: a very strong deformation of space-time. For scientists, this can be translated as an opportunity for reconciliation between the laws of gravity and the world of quantum physics.“The Theory of General Relativity predicts that photons emitted by the gas falling into a black hole should travel along curved trajectories, forming a ring of light around a ‘shadow’ corresponding to the location of the black hole,” Event Horizon Telescope (EHT) stated on its website."This data set has a lot of puzzles in it," concluded Dr. Ricci. "But that's exciting, because it means we're learning something new about the universe.”Zachary Keyser, Cassandra Gomes-Hochberg and Tamar Beeri contributed to this report.
