JWST Finds Three Feeding Supermassive Black Holes in One Early Galaxy
Three actively feeding supermassive black holes are packed into one galaxy seen as it existed about 1.2 billion years after the Big Bang. Yet the James Webb Space Telescope could not directly resolve the two central objects as separate points. Researchers instead found the trio by dissecting the galaxy’s light using the motion of hydrogen gas and small spatial shifts in its spectral signal to identify sources that an unresolved observation likely would have recorded as one.
The international team led by the Max Planck Institute for Extraterrestrial Physics studied J0148-4214, a galaxy at redshift 5.02 whose light traveled more than 12.5 billion years to Earth. The work, published in Astronomy & Astrophysics, identified two black holes in the central region and a third about 5,500 light-years from the center.
Hydrogen supplied the first clue
A feeding black hole cannot be observed directly, but gas falling through its surrounding accretion flow can emit a distinctive spectrum. In J0148-4214, the researchers found hydrogen-emission signatures associated with gas moving at high velocity in the black holes’ gravitational fields.
The central spectrum was too complex to fit a simple picture of one active source. The team concluded that it was best explained by two nearby black holes, although those objects remain too close together on the sky for JWST to show them as two discrete points.
That distinction matters. An image asks where light appears; spectroscopy separates that light by wavelength and therefore carries information about gas motion. JWST’s Near-Infrared Spectrograph integral-field system goes further by collecting a spectrum across different positions in the target. This creates a spatially resolved data set rather than one blended spectrum for the entire galaxy.
The researchers then applied spectro-astrometry, measuring subtle changes in the apparent position of emission at different wavelengths. Those shifts let them assign the central hydrogen signals to two locations. Their projected separation is approximately 620 light-years. That is a two-dimensional distance measured across the sky, not a complete three-dimensional separation.
The third source was less entangled with the central emission. Its high-velocity hydrogen signature appeared in the galaxy’s outer region, roughly 5,500 light-years from the center. According to the team, only one of the three black holes likely would have been detected without the spatial information supplied by JWST’s integral-field spectroscopy.
Three black holes, three different growth states
The estimated masses are highly uneven: about 80 million, 600,000 and 2 million times the Sun’s mass. For context within the system, the galaxy’s total stellar mass is estimated at approximately 1.3 billion solar masses.
The smallest central object is also the more aggressive feeder. The researchers describe the 600,000-solar-mass black hole as accreting above the Eddington limit predicted by basic growth theories, while the 80-million-solar-mass object is taking in material more slowly. The Eddington limit represents the point at which outward radiation pressure is expected to balance the inward pull driving accretion under a simplified, steady model. An above-limit estimate therefore highlights how rapidly the smaller object is growing, rather than implying that black-hole feeding has an inviolable speed cap.
The two central black holes are expected to merge within the next few hundred million years. That makes the galaxy a useful early-universe case for studying how mergers may have helped black holes gain mass quickly, while also informing the kinds of massive mergers future gravitational-wave observatories are intended to detect.
The third object keeps the history unsettled
The off-center black hole’s origin has not been established. It could be a remnant of an earlier merger, an object displaced from the center by gravitational recoil, or a black hole still migrating inward. The available observations do not determine which scenario is correct, nor does its projected position alone reconstruct its full motion through the galaxy.
That uncertainty is part of the result rather than a defect in it. JWST has exposed a system more complicated than a single bright galactic nucleus, while leaving its assembly history open to further observation. The immediate technical result is firmer: spatially resolved spectra can separate active black holes even when a telescope cannot render every one of them as an individual point of light.
By David Whitaker — Associate editor for AMI’s aerospace and drone systems desk, translating flight systems, aircraft programs, spaceflight, and UAV developments into accessible technical stories.
