Using the powerful James Webb Space Telescope (JWST), astronomers have discovered a remarkable supermassive black hole from a period of the early cosmos known as “cosmic noon,” approximately 4 billion years after the Big Bang. This discovery sheds new light on how these behemoths, millions or even billions of times the mass of our sun, grow to such immense sizes.
The Mystery of “Little Red Dots”
JWST has been revealing a new class of intriguing objects in the early universe, dubbed “little red dots.” These are small, bright specks of light only recently detectable thanks to JWST’s advanced infrared capabilities. While their name suggests small size, one recent find, nicknamed “BiRD” (Big Red Dot), is far from diminutive— possessing a mass equivalent to 100 million suns.
How Black Holes Shine
Black holes themselves don’t emit light; their intense gravity traps any that falls in. However, when surrounded by abundant matter and actively feeding, they create incredibly bright objects called quasars. The light from these quasars can travel vast distances, with BiRD’s light having journeyed over 10 billion years to reach Earth.
Locating BiRD
BiRD was identified in the same region of the sky as a previously known quasar, J1030+0524 (J1030), a supermassive black hole already feeding on matter and located roughly 12.5 billion light-years away. The research team from the National Institute for Astrophysics (INAF) initially analyzed images and spectra from JWST’s Near-Infrared Camera (NIRCam) instrument, detecting an unusual point of infrared light that hadn’t been revealed by earlier X-ray and radio observations.
“Starting from the calibrated images, a catalog of the sources present in the field was developed,” explained Federica Loiacono, team leader and INAF research fellow. “It was there that we noticed BiRD: a bright, point-like object, which, however, was not a star and did not appear in the existing X-ray and radio catalogs.”
Analyzing the Spectrum: Unlocking Secrets
The team’s analysis of BiRD’s spectrum, a detailed breakdown of the light’s wavelengths, provided crucial information. Different elements absorb and emit light at specific frequencies, leaving unique “fingerprints” in the spectrum. This allowed researchers to identify the presence of hydrogen and helium in BiRD’s environment.
“We found clear signals of hydrogen — in particular the line called Paschen gamma, a luminous signature that reveals the presence of ionized hydrogen — and helium, also visible in absorption,” Loiacono said. This spectral analysis also provided an estimate of BiRD’s distance and mass.
What Makes BiRD Unique?
Little red dots, in general, remain a cosmic puzzle. Theories abound, including the possibility that they represent a new type of celestial object called “black hole stars.” However, the absence of strong X-ray emission from these objects is perplexing, as ravenous black holes are expected to produce intense X-rays. A possible explanation is that these objects are still shrouded by thick shells of gas and dust, absorbing X-ray radiation while allowing infrared light to pass through.
BiRD is particularly notable because its properties closely resemble only two other known little red dots exhibiting similar spectral characteristics. This suggests they belong to the same family of objects.
Rethinking Black Hole Evolution
The discovery of BiRD and its family may require a reassessment of how supermassive black holes grow and evolve. Previous calculations suggested these objects should have become less common around 11 billion years ago. However, this team’s calculations indicate a surprising abundance of little red dots during “cosmic noon,” challenging that assumption.
“The challenge now is to extend the study to a larger number of nearby LRDs, which we can study in greater detail than distant ones, to build a more complete picture,” Loiacono concluded. “JWST has opened a new frontier in extragalactic astrophysics, revealing objects we didn’t even suspect existed, and we’re only at the beginning of this adventure.”
The discovery of BiRD underscores the power of the James Webb Space Telescope in revealing previously unseen details about the early universe and its inhabitants, prompting a deeper understanding of the formation and evolution of massive black holes.
