The Chicken or the Egg of the Universe: A New Twist
The age-old philosophical conundrum of the chicken or the egg has been a topic of debate for centuries, but now, a team of researchers from the University of Cambridge has brought a fresh perspective to this age-old question, but in the context of the cosmos. The question is: which comes first, the galaxy or the black hole? This is the astronomical equivalent of the chicken or the egg debate, and it has kept astronomers up at night for decades.
The conventional wisdom is that large stars within existing galaxies collapse to form black holes, which then merge to become supermassive black holes. However, the discovery of black holes millions to billions of times the mass of the Sun in the early universe has left astronomers scratching their heads. How could these massive black holes have formed from such small seeds?
This is where the James Webb Space Telescope comes in. Led by the University of Cambridge, an international team of researchers used the telescope to detect clear observational evidence that some supermassive black holes were enormous from the beginning. These black holes formed without going through a stellar collapse phase and without a significantly more massive host galaxy to feed them.
The discovery of Abell2744-QSO1, or QSO1, is a remarkable finding. This crimson dot existed just 700 million years after the Big Bang and is more than 13 billion light years away. It is magnified and appears in three different locations in the sky because it is 'gravitationally lensed' by a galaxy cluster called Pandora's Cluster. QSO1 was initially believed to be a cloud of glowing hydrogen and helium gas circling a supermassive black hole, but the researchers found that the gas has Keplerian rotation, meaning it orbits a central point in the same way that planets in our solar system orbit the Sun.
This is important because it tells us that most of the mass of QSO1 is concentrated in the black hole at the centre. If the mass were more distributed, as it would be if there were a lot of stars, the gas would not have this perfect Keplerian rotation. The researchers were able to calculate the black hole mass directly, confirming that it is immense - roughly 50 million solar masses - and makes up two-thirds of QSO1’s total mass.
This is a phenomenal result. It is the first direct measurement of a black hole mass within the first billion years after the Big Bang, and it is consistent with previous measurements. It suggests that assumptions used for indirect mass measurements are valid and that the masses of other black holes in the early universe have not been overestimated. The outsized mass of QSO1 relative to its host galaxy suggests it cannot have formed gradually from much smaller, stellar-mass black holes merging and feeding.
In my opinion, this discovery is a game-changer. It suggests that supermassive black holes may have predated the galaxies where they are currently found. This is very exciting because it is evidence for primordial black holes or direct collapse black holes, which have been theorised but have not been confirmed. QSO1’s black hole may have evolved from a 'heavy seed' that formed within the first second of the big bang or later from the collapse of a giant cloud of gas. But it was almost certainly born big - and may be in the early stages of building a galaxy around it.
The researchers believe that Little Red Dots like QSO1 cannot have been rare in the early universe. They are now analysing similar objects to find out whether supermassive black holes do predate the galaxies where they are currently found. This raises a deeper question: what does this mean for our understanding of galaxy formation and evolution? It seems that we have found a black hole that does not have a substantial host galaxy and that has predated stellar processes. This is a fascinating development, and it opens up a whole new area of research.
In conclusion, the discovery of Abell2744-QSO1 is a significant step forward in our understanding of the early universe. It challenges our assumptions and raises new questions. It is a testament to the power of modern astronomy and the importance of continued exploration. As we continue to peer into the cosmos, we may just find that the chicken or the egg debate has a new twist in the astronomical realm.
