A supermassive black hole lies at the heart of every galaxy, including the Milky Way. When a black hole is active, it pulls material in as a whirpool of high-temperature gas and dust. As this cosmic material piles up and falls onto a black hole, it\u00a0lights up its vicinity, radiating a huge amount of energy.\u00a0<\/p>\n
The most energetic supermassive black holes are known as quasars, and they are some of the most active and luminous objects in the universe. These voracious systems take in so much material that the energy they emit can outshine all the light in the surrounding galaxy. The pattern of light from a quasar can give scientists clues to how active supermassive black holes shape the galaxies around them.\u00a0<\/p>\n
Now astronomers at MIT and elsewhere have detected a quasar flickering from the very early universe. The scientists traced the light from the quasar back to the \u201ccosmic dawn,\u201d just 850 million years after the Big Bang. The discovery represents the earliest flickering quasar detected to date.\u00a0<\/p>\n
\u201cAlthough there have been a lot of quasars found in the cosmic dawn, this is the first time we actually see one flickering,\u201d says Gene Leung, a postdoc in the MIT Kavli Institute for Astrophysics and Space Research.\u00a0<\/p>\n
The quasar\u2019s flicker enabled the researchers to determine that, surprisingly, the ancient quasar\u2019s whirpool of gas and dust, known as an accretion disk, resembled a flat pancake, similar in shape to that of more modern-day quasars.\u00a0<\/p>\n
Their findings add to a longstanding mystery in cosmology: Why do supermassive black holes exist so early in the universe\u2019s history? Physicists have assumed that a flat accretion disk reflects a relatively mature black hole that is in a calm and stable state. Black holes that are just starting to form, like those in the very early universe, should be more unsettled systems, with accretion disks that appear more puffy and chaotic.\u00a0<\/p>\n
The flat accretion disk around this very early quasar heightens the mystery of how supermassive black holes can grow and mature in a very short amount of cosmic time.\u00a0<\/p>\n
\u201cI think what this suggests is\u00a0that \u00a0all the messy, very rapid growth phases that\u00a0we expect all\u00a0black holes\u00a0to go through\u00a0at some point\u00a0happen very, very early on, before we see them as these very bright luminous\u00a0quasars,\u201d says Anna-Christina Eilers, assistant professor of physics at MIT. \u201cThat\u2019s the picture that\u2019s emerging.\u201d<\/p>\n
Eilers, Leung, and their colleagues report their results in a paper appearing today in Nature Astronomy. Their co-authors include members of MIT Kavli and multiple other institutions.\u00a0<\/p>\n
Past a pinprick<\/strong><\/p>\n A supermassive black hole can be billions of times more massive than the sun. These gravitational giants are the central \u201cengines\u201d of most galaxies, helping to regulate a galaxy\u2019s star formation and growth.\u00a0<\/p>\n \u201cWithout supermassive black holes, no galaxy would look the way it does today,\u201d Eilers says. \u201cBlack holes play a major role in shaping how galactic ecosystems look.\u201d<\/p>\n It was long assumed that it should take more than a billion years for the first galaxies to settle and mature, so scientists didn\u2019t expect to see supermassive black holes in the very early universe. But observations\u00a0since the early 2000s showed otherwise.\u00a0Scientists have\u00a0spotted\u00a0more than 200 supermassive black holes in the universe\u2019s first billion years. Such objects were detectable because they were in an extremely active quasar phase, giving off enormous blasts of radiation that could be seen from Earth, 13 billion light years away.\u00a0<\/p>\n These earliest quasars were observed as pinpricks of light, which signal the existence of a supermassive black hole at early times. But from these bright and distant dots, scientists aren\u2019t able to tell much more about the black holes and their cosmic dawn environments. To do so, they need to catch a quasar\u2019s \u201cflicker.\u201d<\/p>\n \u201cPeople have known that quasars in the nearby universe can flicker,\u201d Leung says. \u201cThe flickering comes from fluctuations in the way the gas is being fed into the black hole. And how a quasar flickers tells us something about the structure of a black hole\u2019s accretion disk, and the kind of \u2018bites\u2019 that the black hole is eating.\u201d<\/p>\n Mapping a flicker<\/strong><\/p>\n Leung and Eilers looked to detect a flickering quasar from the early universe in hopes of learning more about the shape and structure of the earliest supermassive black holes. To do so would be a technical challenge: The further back in time and space an object is, the more distorted its light appears. This effect is due to the expanding universe, which effectively stretches, or \u201credshifts\u201d light to redder, longer wavelengths. The same stretching occurs in time: Any flicker that naturally occurs\u00a0over several\u00a0weeks, for instance, would appear stretched out, flickering\u00a0only every few months when seen from billions of light years away.\u00a0<\/p>\n To spot a flickering quasar from the cosmic dawn, the team needed to observe the distant universe at redder wavelengths, and specifically within the infrared spectrum, and over long timescales of many years.\u00a0<\/p>\n \u201cThis was the technical challenge we had to overcome,\u201d Eilers says. \u201cWe needed data\u00a0at longer, infrared wavelengths taken repeatedly over very long timescales.\u201d\u00a0<\/p>\n The team ultimately found a flicker in data collected by NASA\u2019s\u00a0Near-Earth Object Wide-field Infrared Survey Explorer\u00a0(NEOWISE)\u00a0mission \u2014 a space-based infrared telescope that scanned the entire sky over a total of about 14 years. Former MIT postdoc Kishalay De, who is now a faculty member at Columbia University, had launched a project to re-process\u00a0archival data from NEOWISE.\u00a0Based on the re-processed data,\u00a0the team unearthed a signal, from just 850 million years after the Big Bang,\u00a0which was confirmed to be the earliest flickering quasar.\u00a0<\/p>\n \u201cWe saw the quasar flickering randomly over the 14-year period, much like a candle\u2019s flame flickers without a fixed pattern,\u201d Leung notes.\u00a0<\/p>\n They estimate that the quasar is as bright as 12 trillion suns, and it is flickering by about 20 percent, meaning that it fluctuates up and down, by a brightness of about 2 trillion suns.\u00a0<\/p>\n The researchers also tracked how the quasar\u2019s light flickered over several different wavelengths. The wavelength of light reflects a certain temperature of the material that is emitting the light. The closer material is to a black hole, the hotter it is. Researchers can therefore use wavelengths of light to map the shape and structure of material\u00a0within the accretion disk\u00a0around a black hole.\u00a0<\/p>\n Using NEOWISE data, the team analyzed the quasar\u2019s flicker to determine the shape of the accretion disk surrounding the central supermassive black hole. They found that the disk is surprisingly thin and flat \u2014 a structure that astronomers mostly see around nearby, older black holes, that have had much longer to settle and mature.\u00a0<\/p>\n \u201cThis provides direct evidence that the same feeding processes and structures observed in the nearby universe were already in place at very early times, despite very different cosmic environments, which had never been seen before,\u201d Eilers says.\u00a0<\/p>\n \u201cThis means something happened even earlier on that led to these systems to look so mature,\u201d Leung adds.\u00a0<\/p>\n The team hopes to peer even further back in cosmic time to catch a quasar\u2019s earlier, premature development. Then, scientists can start to piece together the conditions that brewed up the first supermassive black holes.\u00a0<\/p>\n This research was supported, in part, by NASA.<\/p>\n","protected":false},"excerpt":{"rendered":"A supermassive black hole lies at the heart of every galaxy, including the Milky Way. 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