Cosmic Sprinter: Black Hole and Its Galaxy Grow in a Race express
Imagine a city where a skyscraper and a huge park are being built at the same time. The skyscraper grows upward, and the park expands outward. Both processes are fast and get in each other's way, but in the end they are meant to become a single whole. That's the situation in galaxy GNz7q: a black hole grows at the center while new stars burst to life around it.
The James Webb Telescope has now examined this galaxy in detail. It turns out that at its heart sits a black hole with a mass of about 35 million Suns. It is sucking in gas so rapidly that it shines brighter than calculations would suggest. At the same time, a stellar rain is falling across the galaxy: about 330 new Suns are born every year. For comparison, our Milky Way produces just one or two stars per year.
The scientists compared GNz7q with other young galaxies recently found by Webb. Many of them, the so-called "little red dots," barely form stars — only the black hole is active. But GNz7q does both. This suggests it could evolve into a giant elliptical galaxy with a black hole of billions of Suns — the kind we see closer to our own time.
In this way, GNz7q becomes a bridge between early oddities and mature giants. It shows how a black hole and stars can grow hand in hand, not hindering each other but rather fueling a shared growth.
Original abstract
as written by the authors arXiv:2602.12325
We present a panchromatic optical-mm characterization of GNz7q, a recently identified X-ray weak, rapidly growing red quasar embedded within a dusty starburst galaxy at $$z=7.1899$$, using the full suite of JWST/NIRCam, NIRSpec, MIRI, and archival NOEMA observations. Our deep NIRSpec/G395M spectroscopy reveals unambiguous broad Balmer emission (FWHM $$=2221\pm20$$kms$$^{-1}$$), confirming a super-Eddington accreting black hole ($$\lambda_{\rm Edd}=2.7\pm0.4$$) with a mass of $$\log(M_{\rm BH}/M_{\odot})=7.55\pm0.34$$, using accretion-rate corrected BH mass estimators. After subtracting the point source, we robustly detect stellar emission from the host galaxy across multiple NIRCam and MIRI filters. Out joint morphological-spectral analysis yields a stellar mass of $$\log (M_*/M_\odot)=10.5\pm0.4$$ and an intense star formation rate of $${\rm SFR}=330\pm97\,M_\odot\,\rm yr^{-1}$$, confirming the host as a massive, dusty starburst galaxy. We find that GNz7q lies on the local $$M_{\rm BH}$$-$$M_*$$ relation ($$M_{\rm BH}/M_*\simeq 0.001$$) and is well positioned to evolve into the locus of massive SDSS quasars with $$\log (M_{\rm BH}/M_\odot)\approx 9$$ and $$M_*\approx 10^{11}\,M_\odot$$ at $$z\sim 6$$, owing to its remarkably rapid growth in both the black hole and its host galaxy. This stands in stark contrast to many recently reported JWST AGN populations at similar redshifts, including the little red dots (LRDs), whose weak or undetected star formation makes it difficult for them to grow into the massive galaxies hosting SDSS-like quasars. These results suggest that GNz7q marks as a rare, pivotal phase of early BH-galaxy co-eolution, plausibly providing a crucial direct pathway to the supermassive black hole systems within the first billion years of the Universe.
In galaxy GNz7q, stars are born 300 times faster than in the Milky Way. If our Milky Way were producing stars at that rate, the night sky would be hundreds of times brighter.
In Dan Simmons's novel "Hyperion," there is a planet where time flows differently due to its proximity to a black hole. GNz7q is a real example of how extreme conditions can affect an entire galaxy.