Four years ago, the supermassive black hole hidden in the heart of galaxy SDSS1335+0728 roared awake and announced its presence with a blast of radiation. It marks the first time astronomers witnessed a sudden activation of a supermassive black hole in real time.<\/p>\n
<\/p>\n \u201cImagine you\u2019ve been observing a distant galaxy for years, and it always seemed calm and inactive,\u201d said Paula S\u00e1nchez S\u00e1ez, an astronomer at ESO in Germany and lead author of the study of this object. \u201cSuddenly, its [core] starts showing dramatic changes in brightness, unlike any typical events we\u2019ve seen before.\u201d<\/p>\n This is what happened to SDSS1335+0728, which is now officially classified as having an active galactic nucleus (AGN). It experienced what\u2019s called a \u201cnuclear transient.\u201d Essentially, that means the galaxy now has a very bright compact region. However, it wasn\u2019t always that bright and astronomers want to understand what caused it to wake up.<\/p>\n The unusual brightness variations were detected by the Zwicky Transient Facility in California, which gives constant, real-time alerts about such things as transient flaring and brightening in the hearts of galaxies like SDSS1335+0728. In addition, several other facilities observed the variations, too, and brightness changes were found in archival data from several other observatories.<\/p>\n The sudden brightenings could be due to many things, including the cannibalization of stars and clouds of gas that stray too near supermassive black holes. How often they brighten and how a quiescent galaxy nucleus changes to an active one are topics that astronomers are using such surveys and observations to understand. They\u2019re looking not just at distant galaxies, but activity within the neighborhood of our own galaxy\u2019s supermassive black hole, too.<\/p>\n Most galaxies have stupendously massive black holes at their hearts. They typically sequester away at least a hundred thousand times the mass of the Sun (sometimes more). It\u2019s all trapped by gravity and nothing ever escapes, not even light. \u201cThese giant monsters usually are sleeping and not directly visible,\u201d said study co-author Claudio Ricci, from Chile\u2019s Diego Portales University. \u201cIn the case of SDSS1335+0728, we were able to observe the awakening of the massive black hole, [which] suddenly started to feast on gas available in its surroundings, becoming very bright.\u201d<\/p>\n A black hole itself doesn\u2019t emit any light at all. Instead, it sucks everything in, including light. However, the region around the black hole\u2014called the accretion disk\u2014is a pretty active place. It\u2019s where material trapped by the intense gravitational pull of the black hole swirls around like water going down a drain. All that stuff\u2014mostly gas, some dust\u2014is threaded through with magnetic fields. Friction between accretions of the material heats it up. And, that act of heating gives off radiation. If there\u2019s enough of it, we see light being given off. Intense active regions emit x-rays, which indicate the level of activity.<\/p>\n There\u2019s also something called tidal disruption, which happens when something like a star or a cloud of gas gets trapped in the gravitational field. These things take time\u2014on the order of years to occur. When they happen, the gravitational pull of the black hole eventually rips the star or cloud apart. That also gives off radiation. In fact, a very slow-motion tidal disruption event may be occurring at the heart of SDSS1335+0728. If so, it could be one of the longest and dimmest ones ever seen. <\/p>\n Regardless of what\u2019s causing the brightening, the ultimate fate of some of the material is to end up inside the black hole. The rest of it gets superheated in the accretion disk and signals its fate through increased radiation.<\/p>\n The supermassive black holes in the hearts of galaxies grow from smaller ones to larger ones through mergers. We don\u2019t see those growth patterns in real time, since they occur over millions of years. The merger scenario says that when galaxies come together, their central black holes (if they have them) do, too. <\/p>\n Eventually you get these gargantuan monsters. They just sit there and nibble away at passing gas clouds to gain additional mass. That\u2019s how they gain mass through acquisitions, which occur over shorter timescales. This is apparently what the one in SDSS1335+0728 is doing now. It\u2019s just not often that astronomers get to see one wake up and start munching away in a short period of time.<\/p>\n So, a lot of questions remain about this one, mostly about its formation history. Since the mergers take a long time, it\u2019s hard to know what\u2019s happened to this one in the past. If this is a tidal disruption event, astronomers want to know how often such things happen.<\/p>\n At the moment, for SDSS1335+0728, there\u2019s no immediate evidence of prior outbursts signaling prior awakenings of the supermassive black hole. Astronomers need to do a lot of follow-up observations to understand what\u2019s really happening there, and perhaps find evidence for other eruptions and activity associated with the black hole, according to S\u00e1nchez S\u00e1ez. \u201cRegardless of the nature of the variations, [this galaxy] provides valuable information on how black holes grow and evolve,\u201d she said, noting that advanced instruments at ESO\u2019s Very Large Telescope should give astronomers a better idea of the processes occurring at this black hole. In addition, further time-domain all-sky surveys with the upcoming Vera C. Rubin telescope should be able to track this galaxy\u2019s nuclear brightenings.<\/p>\n Astronomers See a Massive Black Hole Awaken in Real TimeLooking for Transients in all the Right Places<\/h3>\n
A Galaxy and Its Supermassive Black Hole<\/h3>\n
Gravity\u2019s Slice-and-dice Activity<\/h3>\n
Black Hole Growth and a Wake-up Call<\/h3>\n
![\"Simulation](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2023\/06\/merger-580x327.jpg\")
![\"This](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2017\/02\/tidal_illus-580x487.jpg\")
For More Information<\/h4>\n
SDSS1335+0728: The awakening of a ~10^6 M_sun Black Hole
arXiv preprint<\/p>\nLike this:<\/h3>\n