While probing the dawn of the universe for the origins of ancient galaxies, the James Webb Space Telescope has discovered something unexpected lurking in their cores—a discovery that could reshape our view of the early cosmos.
Scientists have long believed that galaxies evolve, and that black holes at the center are formed after the collapse of massive stars. Webb’s latest observations, however, tell a different story. The telescope proved that supermassive black holes first evolved without a galaxy to feed them.
Webb’s observations may finally answer the celestial chicken-or-egg question, suggesting that ancient black holes don’t need to consume large amounts of surrounding gas and dust to grow to massive sizes.
“This is a remarkable finding,” said Roberto Maiolino, a researcher at the University of Cambridge and co-author of the two studies. Nature and Monthly Notices of the Royal Astronomical Societysaid a NASA statement. “This is a paradigm shift, a revision of the classic scenarios of how black holes form and grow.”
A look back
Webb named one of the first small glowing spots of infrared light that he found Abell2744-QSO1 (QSO1), It dates to just 700 million years after the Big Bang (5% of its current age). The prototypical Small Red Dot is gravitationally lensed by the galaxy cluster Abell 2744. This makes it an ideal target because it is magnified and triple imaged.
Early observations of QSO1 suggest that it might A supermassive black hole about 40 million times the mass of the Sun surrounding a cloud of glowing hydrogen and helium gas. However, scientists were not sure if the black hole was really that big.
“Before now, the masses of all black holes in the early universe were inferred from what we knew about them in the local universe. We didn’t know if those assumptions actually applied to the distant universe,” said Francesco D’Eugenio, a researcher at the University of Cambridge and co-author of the study.
The weight of the animal
To confirm the black hole’s mass, the research team tracked the effect of its gravity on the gas swirling around it and mapped the distribution of various elements in the gas. Using Webb’s Near-Infrared Spectrograph (NIRSpec), scientists discovered that the gas orbits a central point in the same way that the planets in the Solar System orbit the Sun. This phenomenon is known as Kepler motion.
“This is important because it tells us that most of the mass of QSO1 is concentrated in the central black hole,” said Ignas Juodžbalis, a graduate student at the University of Cambridge and lead author of one of the studies. “If the mass was more distributed, if there were more stars, the gas wouldn’t have this perfect Kepler rotation.”
Since Kepler’s motion is governed by the laws of gravity, the team used measurements of the velocity of the surrounding gas to directly calculate the black hole’s mass. “It’s a phenomenal result,” Maiolino said. “This is the first direct measurement of the mass of a black hole during the first billion years after the Big Bang, and is consistent with previous measurements.”
The results revealed that the black hole is not only supermassive, 50 million times the mass of the Sun, but also about two-thirds the total mass of QSO1. Supermassive black holes generally make up only a small fraction of the total mass of their host galaxies. The discovery revealed a ratio between the supermassive black hole and its galaxy that is thousands of times larger than that of nearby galaxies.
The findings suggest that this black hole was born as a big boy, rather than forming from a collapsing star and feeding on the surrounding gas to grow to its massive size. The chemical composition of QSO1 also showed that it is composed almost entirely of hydrogen and helium, with very little of the heavier elements such as oxygen typically found in galaxies rich in stars and stellar debris.
“It seems that we have found a black hole that does not have a host galaxy and that predates stellar processes,” Juodzhbalis said. “This is very exciting because it is theorized but unproven evidence of primordial black holes or black holes collapsing directly.”
