Unraveling the Mystery of Black Holes and Galaxies
Do black holes or galaxies form first? This age-old question has been a subject of debate for scientists for a long time. Traditionally, it's been thought that large stars within a galaxy consume their fuel and then collapse, forming black holes. These black holes can then devour surrounding material and merge over time to create bigger entities.
However, it's been a challenge to explain how black holes, millions to billions of times the size of the Sun, could have grown so quickly from such small beginnings. Especially, considering that thousands of these massive black holes have now been detected in the early universe.
A Remarkable Discovery
Latest research reveals that some supermassive black holes were already enormous from the outset, forming without going through a stellar collapse phase and without a significantly more massive host galaxy to feed them. This discovery is considered a game changer, completely altering the traditional understanding of how black holes form and grow.
Focus on a Unique Red Dot
The research team's conclusion is based on detailed observations of a unique Red Dot, known as Abell2744-QSO1 (QSO1), that existed just 700 million years after the big bang. Despite being only 1,300 light-years across and its light having traveled for over 13 billion years, QSO1 is easier to study than most other Red Dots because it is gravitationally lensed, meaning it is both magnified and triply imaged, appearing in three different locations in the sky.
Understanding Black Hole Mass
Initial studies of QSO1 suggested it was little more than a glowing cloud of hydrogen and helium gas revolving around a supermassive black hole estimated to be 40 million times the mass of the Sun. However, there was uncertainty about whether it was indeed that massive.
Until now, all mass measurements of black holes in the early universe were indirect, based on assumptions from what we know about them in the local universe. It was unclear if those assumptions were applicable to the distant universe.
Observing and Calculating the Mass
The researchers identified that if QSO1's black hole was as massive as it appeared, they should be able to trace the effects of its gravity on the gas swirling around it, while also mapping the distribution of various elements in the gas.
Using these observations, the research team was able to map the motions of hydrogen gas surrounding the black hole. When they plotted the rotation velocity as a function of distance from the center, they discovered that the gas has Keplerian motion, meaning it orbits a central point in the same way that planets in our solar system orbit the Sun.
This was a crucial finding because it indicated that most of the mass of QSO1 was concentrated in the black hole at the center. If the mass were more distributed, as it would be with many stars, the gas wouldn't exhibit this perfect Keplerian rotation.
Because Keplerian motion is governed by simple laws of gravity, the team was able to use the gas velocity measurements to calculate the black hole mass directly - something that hadn't been possible before.
Unveiling the Truth About Black Holes
They found that the black hole is enormous, approximately 50 million solar masses, and makes up at least two-thirds of QSO1's total mass. This proportion is thousands of times greater than in nearby galaxies, where supermassive black holes make up only a tiny fraction of the host galaxy's total mass.
This is a phenomenal result and it's consistent with previous measurements. The team believes this is a positive sign that the assumptions used for indirect mass measurements are valid and the masses of other black holes in the early universe have not been overestimated.
Probing into the Origins of Supermassive Black Holes
The extraordinary mass of QSO1 relative to its host galaxy suggests that it didn't form gradually from smaller, stellar-mass black holes merging and feeding. It seems to be a black hole that doesn't have a substantial host galaxy and that predates stellar processes. This is exciting because it provides evidence for primordial black holes or direct collapse black holes, which have been theorized but not confirmed.
Whether QSO1's black hole evolved from a "heavy seed" that formed within the first second of the big bang or somewhat later from the collapse of a giant cloud of gas, it was almost certainly born big, and may be in the early stages of building a galaxy around it.
The team believes that Red Dots like QSO1 were not uncommon in the early universe, and they're currently analyzing similar objects to find out whether supermassive black holes actually do predate the galaxies where they currently reside.
Do black holes or galaxies form first? This age-old question has been a subject of debate for scientists for a long time. Traditionally, it's been thought that large stars within a galaxy consume their fuel and then collapse, forming black holes. These black holes can then devour surrounding material and merge over time to create bigger entities.
However, it's been a challenge to explain how black holes, millions to billions of times the size of the Sun, could have grown so quickly from such small beginnings. Especially, considering that thousands of these massive black holes have now been detected in the early universe.
A Remarkable Discovery
Latest research reveals that some supermassive black holes were already enormous from the outset, forming without going through a stellar collapse phase and without a significantly more massive host galaxy to feed them. This discovery is considered a game changer, completely altering the traditional understanding of how black holes form and grow.
Focus on a Unique Red Dot
The research team's conclusion is based on detailed observations of a unique Red Dot, known as Abell2744-QSO1 (QSO1), that existed just 700 million years after the big bang. Despite being only 1,300 light-years across and its light having traveled for over 13 billion years, QSO1 is easier to study than most other Red Dots because it is gravitationally lensed, meaning it is both magnified and triply imaged, appearing in three different locations in the sky.
Understanding Black Hole Mass
Initial studies of QSO1 suggested it was little more than a glowing cloud of hydrogen and helium gas revolving around a supermassive black hole estimated to be 40 million times the mass of the Sun. However, there was uncertainty about whether it was indeed that massive.
Until now, all mass measurements of black holes in the early universe were indirect, based on assumptions from what we know about them in the local universe. It was unclear if those assumptions were applicable to the distant universe.
Observing and Calculating the Mass
The researchers identified that if QSO1's black hole was as massive as it appeared, they should be able to trace the effects of its gravity on the gas swirling around it, while also mapping the distribution of various elements in the gas.
Using these observations, the research team was able to map the motions of hydrogen gas surrounding the black hole. When they plotted the rotation velocity as a function of distance from the center, they discovered that the gas has Keplerian motion, meaning it orbits a central point in the same way that planets in our solar system orbit the Sun.
This was a crucial finding because it indicated that most of the mass of QSO1 was concentrated in the black hole at the center. If the mass were more distributed, as it would be with many stars, the gas wouldn't exhibit this perfect Keplerian rotation.
Because Keplerian motion is governed by simple laws of gravity, the team was able to use the gas velocity measurements to calculate the black hole mass directly - something that hadn't been possible before.
Unveiling the Truth About Black Holes
They found that the black hole is enormous, approximately 50 million solar masses, and makes up at least two-thirds of QSO1's total mass. This proportion is thousands of times greater than in nearby galaxies, where supermassive black holes make up only a tiny fraction of the host galaxy's total mass.
This is a phenomenal result and it's consistent with previous measurements. The team believes this is a positive sign that the assumptions used for indirect mass measurements are valid and the masses of other black holes in the early universe have not been overestimated.
Probing into the Origins of Supermassive Black Holes
The extraordinary mass of QSO1 relative to its host galaxy suggests that it didn't form gradually from smaller, stellar-mass black holes merging and feeding. It seems to be a black hole that doesn't have a substantial host galaxy and that predates stellar processes. This is exciting because it provides evidence for primordial black holes or direct collapse black holes, which have been theorized but not confirmed.
Whether QSO1's black hole evolved from a "heavy seed" that formed within the first second of the big bang or somewhat later from the collapse of a giant cloud of gas, it was almost certainly born big, and may be in the early stages of building a galaxy around it.
The team believes that Red Dots like QSO1 were not uncommon in the early universe, and they're currently analyzing similar objects to find out whether supermassive black holes actually do predate the galaxies where they currently reside.