The cosmos might contain significantly more gigantic black holes voraciously consuming the matter around them than previously estimated.
This is the determination of a group of researchers, who propose that astronomers could be overlooking between 30% and 50% of active supermassive black holes, enormous celestial bodies with masses resembling millions or even billions of suns.
Don’t fret; these cosmic behemoths aren’t concealed beneath your bed (we assure you would recognize it if they were). Rather, they seem to be concealed behind the extensive layers of galactic gas and dust that sustain them.
“The ratio of a supermassive black hole’s size to its host galaxy is similar to comparing a pea to the Earth,” stated study leader Peter Boorman, a researcher at the California Institute of Technology in Pasadena, during the 245th gathering of the American Astronomical Society in National Harbor, Maryland on Monday (Jan. 13).
“However, despite this vast size discrepancy, an accreting supermassive black hole has the capability to wreak havoc or positively impact its host galaxy,” Boorman remarked.
Related: Black holes: All you need to know
That’s because when black holes “overfeed,” they can emit jets of material from their immediate vicinity at approximately 33% the speed of light. These astrophysical jets can expel the gas and dust essential for their host galaxies to form stars. Consequently, an erupting black hole can hinder or even terminate star formation within its surrounding galaxy.
“This has significant implications for our understanding of galaxy evolution,” Boorman continued. “One aspect of this scenario that is frequently neglected is obscuration.”
Obscuration refers to the concealment of feeding or “accreting” supermassive black holes in otherwise luminous regions known as active galactic nuclei (AGN) by the very plates of gas and dust they consume.
Black holes conceal themselves behind donuts
The Caltech investigator, formerly associated with the University of Southampton in England, clarified that hunger-driven and growing supermassive black holes couldn’t exist without some kind of material reservoir surrounding them — a “cosmic buffet” from which they draw sustenance.
“It’s believed that this aggregate can take on the approximate geometric shape of a donut,” Boorman noted. “Depending on the alignment of that material with respect to our line of sight, we either see directly into the center of the accreting mass, which is very luminous, or we encounter significant obscuration.”
Earlier research has suggested that this obscuration might be concealing as much as 15% of active supermassive black holes from our observation.
Boorman and his colleagues explored this hypothesis using infrared data from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) spacecraft, as part of a project named NuLANDS (NuSTAR Local AGN N H Distribution Survey).
The outcome was the visualization of infrared light emanating from clouds surrounding supermassive black holes. This allowed the team to assemble the first highly precise tally of black holes growing by consuming surrounding matter.
“Although black holes are dark, the surrounding gas heats up and glows vividly, making them some of the brightest entities in the cosmos,” noted team member and University of Southampton researcher Poshak Gandhi mentioned in a statement. “Even while hidden, the surrounding dust absorbs and re-emits this light as infrared radiation, revealing their [black hole’s] existence.
“We’ve discovered that many more are lurking in plain sight — obscured by dust and gas, which renders them unseen to ordinary telescopes.”
Searching for hidden feeding black holes could elucidate how they develop into such immense sizes. It might also aid in painting a clearer picture of how galaxies evolve.
“Without black holes, galaxies might be significantly larger,” Gandhi remarked. “If there weren’t a supermassive black hole in our Milky Way galaxy, there could potentially be many more stars visible in the sky.
“That’s merely one instance of how black holes can shape a galaxy’s evolution.”
Boorman elaborated on how different our perception of the universe would be if we could visualize the existence of these feeding supermassive black holes.
“If our eyes could perceive X-rays, the sky would overflow with dots,” Boorman stated. “And every one of those dots would represent an accreting supermassive black hole.”
The team’s findings were published on Dec. 30 in The Astrophysical Journal.