Supermassive black holes at the centres of galaxies can get absurdly huge, sometimes reaching masses billions of times greater than our Sun. The rate at which black holes grow can vary, but Australian astronomers have detected one such object with an unusually intense appetite, making it the fastest-growing black hole ever detected in the observable universe.
This bloated supermassive black hole has an equally bloated name, QSO SMSS J215728.21-360215.1, or J2157-3602 for short. At 12 billion light-years away, it's not close, so we're observing this bright behemoth not as it is today, but as it existed some four billion years after the Big Bang.
Astronomers with the Australian National University (ANU) used three different instruments to observe this black hole, or quasi-stellar object (QSO) as it's also called: ESA's Gaia satellite, the ANU Siding Spring Observatory, and NASA's Wide-field Infrared Survey Explorer satellite. This research is set to be published in Publications of the Astronomical Society of Australia, but a preprint of the paper has been posted to arXiv.
Observations show that J2157-3602 is the size of about 20 billion suns, and it's growing at a rate of 1 per cent every million years. Every two days, this black hole devours a mass equivalent to our Sun, gobbling up dust, gas, bits of celestial debris, and whatever else it can suck in using its powerful gravitational influence. Astronomers have observed fast-growing QSOs before, but this one is a record setter, making it the fastest-growing and the brightest-glowing black hole ever detected.
Indeed, J2157-3602 is glowing with mind boggling intensity. Its rapid rate of growth is causing it to shine thousands of time more brightly than an entire galaxy. The influx of gases are producing a tremendous amount of friction and heat, resulting in the intense luminosity. The black hole is also spewing ultraviolet light and x-rays at a rate that's rendering the entire galaxy sterile.
"If we had this monster sitting at the centre of our Milky Way galaxy, it would appear 10 times brighter than a full moon. It would appear as an incredibly bright pinpoint star that would almost wash out all of the stars in the sky." Christian Wolf, lead author of the study and an astronomer at ASU, said in a statement. "Again, if this monster was at the center of the Milky Way it would likely make life on Earth impossible with the huge amounts of x-rays emanating from it."
The discovery of J2157-3602 was assisted by Data Release 2 from the Gaia Collaboration, and astronomers observed it further using the Siding Spring Observatory. The Gaia satellite helped confirm its remote location in the cosmos and its status as a QSO.
Supermassive black holes came into existence as early as 800 million years after the Big Bang, but how they grew so big and so quickly after the Big Bang remains a mystery. Moving forward, scientists are hoping to find black holes that are growing even faster than J2157-3602. Work in this area could tell us more about what the conditions were like in the early universe, how elements were formed (especially metals), and how these early black holes may have ionized gases around them, making the universe more transparent.