Lonely quasars in the early universe cannot be explained

Deep in the cosmos, quasars shine brightly. Their luminescent cores showcase the activity of supermassive black holes at the heart of a galaxy.

Tracking quasars back to the early days of the universe, several hundred million years after the Big Bang, a cosmic conundrum emerges. How did these luminous and massive quasars come to be?

Outshining entire galaxies

Quasars, short for “quasi-stellar objects,” are incredibly bright and energetic regions found at the centers of some distant galaxies. They are powered by supermassive black holes that actively consume surrounding material.

As this material (often gas and dust) spirals into the black hole, it heats up and emits enormous amounts of radiation across the electromagnetic spectrum, including visible light, radio waves, X-rays, and gamma rays.

This process makes quasars some of the brightest objects in the universe, often outshining entire galaxies.

Quasars with mysterious origins

Attempting to unravel the mystery of early quasars’ rapid growth, some experts have suggested they emerged from regions abundant with primordial matter. This results in smaller galaxies populating quasar fields.

A study led by astronomers at the Massachusetts Institute of Technology is now challenging this theory.

The researchers uncovered ancient quasars floating alone when the universe was relatively young – between 600 and 700 million years old. 

The experts explained that luminous quasars are expected to reside in massive overdensities at early cosmic times, which implies that one should find a high number of companion galaxies in their vicinity.

Observations challenge prevailing theories

The team used NASA’s James Webb Space Telescope (JWST) to peer back more than 13 billion years. They looked at five quasars and found a staggering diversity in the “quasar fields.”

As predicted by original models, some quasars inhabit crowded fields with more than 50 neighboring galaxies. However, some defy predictions, drifting in isolation with only a small number of galaxies nearby.

These solitary quasars raise questions. How could luminous objects form early in the universe without a significant reservoir of matter to fuel black hole growth?

Quasars in the middle of nowhere

Anna-Christina Eilers, the lead scientist on the project and assistant professor of physics at MIT, elaborated on the study’s findings.

“Contrary to previous belief, we find on average, these quasars are not necessarily in those highest-density regions of the early universe,” noted Eilers. “Some of them seem to be sitting in the middle of nowhere.”

The quasars may not be as solitary as they seem. Galaxies could surround them but be concealed by dust and hidden from view.

The research team aims to fine-tune their observations and seek out clues on how these quasars grew so large (so quickly) in the early universe.

Quasar neighborhoods: A varied landscape

For this study, the scientists used the JWST to investigate the environments of five of the earliest known quasars. Despite their age, the objects still manage to retain their luminosity.

Quasars cast their light across the expanse of the universe and JWST’s sensitive detectors find it.

“It’s just phenomenal that we now have a telescope that can capture light from 13 billion years ago in so much detail,” said Eilers.

“For the first time, JWST enabled us to look at the environment of these quasars, where they grew up, and what their neighborhood was like.”

Lonely quasars and our understanding of the universe

Ultimately, the study creates more questions than answers. The isolation of some quasars goes against models predicting quasar formation in regions populated with smaller galaxies – a result of dark matter attracting gas and dust.

“Our results show that there’s still a significant piece of the puzzle missing of how these supermassive black holes grow,” said Eilers.

“If there’s not enough material around for some quasars to be able to grow continuously, that means there must be some other way that they can grow, that we have yet to figure out.”

The enigma of lonely quasars challenges our understanding of the universe, particularly black hole growth, and pushes scientists to question and refine current models.

The research is published in The Astrophysical Journal.

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