Did the Supermassive Black Hole at the Center of this Galaxy Form Before the Galaxy Itself?
NASA, ESA, STScI, AURA; S. Smartt/Queen’s University Belfast
If we consider the musings of the novelist and philosopher Samuel Butler from 1878, stating that “chickens are simply the means by which eggs produce other eggs,” we might parallel this with galaxies being mere vehicles through which black holes generate further black holes. In this cosmic conundrum, it seems that black holes take precedence.
Every major galaxy observed in the universe is anchored by a supermassive black hole at its heart. This relationship is crucial, as the black hole influences the galaxy’s developmental trajectory by consuming the surrounding matter. Yet, the genesis of this crucial connection poses an enduring enigma in cosmology. Does matter assemble to create black holes, or do sizable galaxies form first and collapse into black holes?
A pivotal element of this discussion revolves around the peculiar nature of supermassive black holes themselves, which seem almost impossible given their enormity. The concept of such massive entities existing merely 500 million years following the Big Bang raises eyebrows. To illustrate, if we condense the universe’s timeline into a single calendar year, the first supermassive black hole would have emerged shortly after the new year, rapidly accumulating mass far exceeding that of our sun. Current physical laws struggle to elucidate how something could grow so swiftly.
Four primary hypotheses exist for the formation of supermassive black holes. The most straightforward involves the merging of stellar-mass black holes, born from collapsing massive stars. However, this process spans hundreds of millions to billions of years, generating a time constraint that complicates the scenario. Another theory posits the creation of significant early seeds—potentially large protostars, dark matter stars, or star clusters. Yet, this too faces timing issues, as these seeds must form swiftly within the universe’s first 500 million years.
This leaves us with two feasible explanations: direct collapse, wherein intense radiation impedes star formation in massive gas clouds, enabling them to become black holes directly, and the controversial primordial black holes theory.
Primordial black holes, although lacking concrete evidence, would create fascinating implications if proven real. Forming in the universe’s nascent moments—not from stars but due to extreme pressures—they could potentially resolve some formation predicaments. While primordial black holes can be smaller than traditional models, our focus here is on the more massive black hole candidates, as these primordial entities likely evolved into significant structures faster than others.
If primordial black holes exist and mechanisms for the early formation of supermassive black holes are validated, then the chicken-and-egg quandary could find resolution. The rapid formation of these black holes implies galaxies might not have developed at comparable speeds, though confirmatory evidence remains elusive.
Thanks to the James Webb Space Telescope (JWST), we now view the cosmic timeline with unprecedented clarity. Observations reveal the presence of supermassive black holes in every era examined. A standout discovery from JWST is a distant galaxy nicknamed the Little Red Dot. While newly uncovered, this discovery also revealed hundreds of further galaxies, characterized by their small size and significant distance.
After thorough investigation, researchers confirmed these entities are indeed galaxies, with their central black holes possessing unusually large masses and impressive spin rates. This remarkable size of black holes raises significant questions, especially after a 2024 study suggested they may constitute 20 to 70 percent of the total mass of their respective galaxies—an anomaly in current understanding.
JWST also uncovered a geometric anomaly that magnified light from a diminutive galaxy known as Abell 2744-QSO1 (or QS01). This observation, made just 700 million years post-Big Bang, enabled astronomers to assess the mass of QS01 and its central black hole. This type of measurement had never been accomplished for a black hole formed within a billion years of the Big Bang. The black hole’s mass was calculated to be roughly 50 million solar masses, with the total galaxy estimated at around 75 million.
Consequently, there are two pathways to interpret these findings: direct collapse or a primordial black hole, neither suggesting that galaxies predated their central black holes. Thus, it appears that the black hole at the center of QS01 is indeed the initial cosmic egg, resolving our query.
However, the complexity persists. We now need to investigate additional tiny red dots to determine whether QS01 is a typical example and to decipher the formation of its black hole and the galaxy’s composition. The ensuing discoveries are likely to unveil more mysteries. Yet, the progress made should be acknowledged, leading us to the undeniable conclusion that “the egg indeed came before the chicken.”
Topic:
Source: www.newscientist.com
