While you might assume that black holes are, well, black, there is a small class of black holes that are oxymoronically bright. Named because they were originally mistaken for distant stars, these quasi-stellar objects, or quasars, are supermassive black holes at the centers of galaxies in the early universe that are actively and violently devouring gas. This accretion process produces large amounts of radiation that astronomers can observe and measure, providing insights into the environments around these black holes.
Recently, a group spearheaded by Yale researchers added a rarity to the population of known quasars with the characterization of J1429+5447, one of the farthest and brightest quasars observed.
Although the accretion of gas onto the quasar emits radiation at almost all wavelengths of light, most areas of the electromagnetic spectrum are contaminated by light from other nearby sources in the quasar’s host galaxy. Only X-rays provide a clean medium to observe quasars without other sources polluting the signal. The study compared archival images from the Chandra X-ray Observatory with recent observations of the quasar from the Nuclear Spectroscopic Telescope Array (NuSTAR) to determine how the brightness of the quasar changes over time. They observed that in just four months between the two observations, the brightness of the quasar doubled. Due to relativistic effects, four months is only two weeks from the perspective of the quasar.
“The variability of this quasar was very fast with a large intensity in flux that is an outlier for typical quasar sources,” said LeaMarcotulli , a NASA Einstein postdoctoral fellow at Yale and the lead author of the study recently published in the Astrophysical Journal Letters. “This led us to conclude that the most likely explanation is that the quasar hosts a jet pointed directly towards us.”The presence of powerful jets in supermassive black holes during the early universe prompts the question of how these black holes grew to these massive sizes in such short periods.
The age of J1429+5447 generates more questions than answers. Though light is the fastest thing in the universe, it is not instantaneous. This means that the history book of the cosmos unravels before us in the night sky. Peering at objects further away from us equates to looking further back in time, closer to cosmic dawn. By looking at the relativistic shift in the wavelength of emitted light from the quasar, scientists know that J1429+5447 existed during the Epoch of Reionization. This period of cosmic history is when neutral hydrogen became re-ionized upon the formation of the first stars and galaxies. The detection of this highly energetic quasar calls for a second look at the role of quasars in the reionization process—perhaps quasars contributed more energy to reionization than scientists previously thought.
The addition of this anomalous quasar complicates astronomers’ picture of the early universe. As the number and diversity of discovered quasars increases, we can better understand the mechanisms that influenced the universe’s evolution and brought us to the structure of the cosmos we see in the night sky today.