Every galaxy, including the Milky Way, hosts a supermassive black hole at its core. When active, these black holes draw in material, forming a hot, swirling mass of gas and dust. As this material accumulates and falls into the black hole, it illuminates the surrounding area with immense energy. Quasars, the most powerful supermassive black holes, emit light that can surpass the combined brightness of their entire galaxy. The light patterns from quasars help scientists understand how active supermassive black holes influence their galaxies.<\/p>\n
Researchers from MIT and other institutions have now identified a quasar flickering from the early universe, tracing its light to the “cosmic dawn,” 850 million years post-Big Bang. This is the earliest known flickering quasar. “Although many quasars have been found from the cosmic dawn, this is the first time we see one flickering,” says Gene Leung, a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research. The flicker revealed that the ancient quasar’s gas and dust disk, or accretion disk, was flat like those of more modern quasars.<\/p>\n
The findings contribute to the ongoing mystery in cosmology regarding why supermassive black holes existed so early in the universe. Physicists previously thought that a flat accretion disk indicated a mature, stable black hole, whereas early black holes should have chaotic, puffy disks. The early quasar’s flat disk deepens the question of how supermassive black holes evolved so quickly. “This suggests the rapid growth phases of black holes occur very early, before they become bright quasars,” says MIT assistant professor Anna-Christina Eilers. Eilers, Leung, and their colleagues published their findings in Nature Astronomy, with contributors from MIT Kavli and other institutions.<\/p>\n
Supermassive black holes, which can be billions of times more massive than the sun, are central to most galaxies, influencing star formation and growth. “Without supermassive black holes, galaxies wouldn’t look as they do now,” Eilers notes. Initially, it was believed that galaxies took over a billion years to mature, so finding early supermassive black holes was unexpected. Since the early 2000s, over 200 supermassive black holes have been discovered from the universe’s first billion years, identified by their active quasar phase and intense radiation visible from 13 billion light years away.<\/p>\n
These early quasars appeared as distant points of light, indicating supermassive black holes at the time. However, these observations didn’t reveal much about their environments. To learn more, scientists needed to observe a quasar’s “flicker.” “Nearby quasars are known to flicker due to gas feeding fluctuations,” says Leung. A quasar’s flicker provides insights into a black hole’s accretion disk structure and the feeding process.<\/p>\n
Leung and Eilers aimed to detect a flickering quasar from the early universe to learn about the earliest supermassive black holes’ shape and structure. This task was technically challenging due to light distortion over vast distances. The universe’s expansion stretches light to longer wavelengths, and flickers occurring over weeks may appear to happen over months when viewed from billions of light years away. To spot a flickering quasar from the cosmic dawn, the team needed to observe at longer wavelengths in the infrared spectrum over extended periods.<\/p>\n
The team discovered a flicker using data from NASA’s NEOWISE mission, an infrared telescope that scanned the sky for about 14 years. Former MIT postdoc Kishalay De, now at Columbia University, reprocessed NEOWISE’s archival data. Using this data, the team found a signal 850 million years after the Big Bang, confirming it as the earliest flickering quasar. “We saw the quasar flickering randomly over 14 years, like a candle’s flame,” Leung reports. The quasar shines as brightly as 12 trillion suns, flickering by 20 percent, or 2 trillion suns.<\/p>\n
Researchers also analyzed the quasar’s light flicker across various wavelengths, which correspond to the temperature of the emitting material. The closer material is to a black hole, the hotter it gets. By examining wavelengths, they mapped the accretion disk around the black hole. The quasar’s disk was unexpectedly thin and flat, a structure usually seen in older black holes that had time to mature. “This shows that early universe feeding processes and structures were already similar to those nearby, despite different cosmic environments,” Eilers explains. “This suggests something occurred earlier that led to these systems appearing mature,” Leung adds.<\/p>\n
The team aims to explore further back in time to observe a quasar’s earlier development phase. This could help scientists understand the conditions that led to the first supermassive black holes. This research received partial support from NASA.<\/p>\n