A supermassive black hole at the centre of an active galactic nucleus in our cosmic “neighborhood” is growing at an exceptionally rapid rate while producing a radio outburst unlike anything previously observed.
Because of its properties, which resemble objects in the much more distant early Universe, this remarkable galaxy offers important insights into the formation and evolution of the first black holes. Led by Stefanie Komossa of the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, an international team of astronomers, including Hungarian researchers, and a student of ELTE investigated the galaxy designated SDSS J110546.07+145202.4. What makes the object special is that since an outburst more than eight years ago, it has remained extraordinarily bright at radio wavelengths. Although the galaxy is not especially distant in cosmological terms – located “only” 1.8 billion light-years from Earth –, its central black hole displays characteristics more typical of rapidly evolving black holes in the early Universe.
Image of the Seyfert galaxy SDSS J110546.07+145202.4 based on a combination of optical and infrared observations. (Credit: DESI Legacy Survey)
The intensity of the radio emission from the nucleus of the spiral galaxy, located in the direction of the constellation Leo, increased by more than a factor of twenty within a short period of time and has shown no signs of fading since then. This exceptional brightening, now lasting for more than eight years, is a unique phenomenon among active galactic nuclei. According to the researchers, this object may represent the first known example of a new class of galaxies showing rapid and long-lasting changes in radio brightness. The source of the emission is the immediate environment of the black hole at the galaxy’s center. The black hole’s mass is relatively low for the supermassive category – amounting to “only” a few million solar masses –, yet it is growing extremely rapidly through accretion. Strong radio emission associated with rapidly growing, low-mass black holes is itself rare, but such a long-lived radio-bright state has never been observed before.
The research team used both new observations and archival data spanning wavelengths from radio to high-energy X-rays. Their analysis suggests that in recent years substantially more material than before has been falling into the black hole, leading to the formation of a jet: a beam of charged particles moving outward at nearly the speed of light. Researchers do not yet know precisely what triggered the enhanced accretion or why the radio outburst has persisted for such a long time.
The relatively low mass and rapid growth are precisely the characteristics expected for the central black holes of galaxies in the early Universe. However, such objects are usually extremely distant, making detailed investigations difficult. SDSS J110546.07+145202.4, by contrast, is relatively nearby on cosmic scales, offering an excellent opportunity to study black hole evolution and jet formation in detail. According to the researchers, events like this may help reveal the physical processes occurring in the most extreme environments in the Universe. In the future, high-resolution very long baseline interferometry (VLBI) networks, such as the European VLBI Network (EVN) and the U.S.-based Very Long Baseline Array (VLBA), will make it possible to map the structure and evolution of the jet in detail. Meanwhile, the highly sensitive Square Kilometre Array (SKA) interferometer currently under construction in the southern hemisphere is expected to discover many similar sudden radio brightening events, contributing to a better understanding of the early Universe and the origin of the first black holes.
The study presenting these new results was recently published in The Astrophysical Journal.
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Hungarian researchers participating in the international collaboration included Krisztina Éva Gabányi (ELTE Eötvös Loránd University HUN-REN─ELTE Extragalactic Astrophysics Research Group and HUN-REN CSFK), Sándor Frey (HUN-REN CSFK), and Attila Mezősi, a student at ELTE.
The discovery of the giant radio outburst itself was reported by members of the team last year in the journal Astronomy & Astrophysics: Gabányi K.É. et al. (2025): Discovery of a giant radio outburst of the narrow-line Seyfert 1 galaxy SDSS J110546.07+145202.4. Astronomy & Astrophysics, 702, L17
Cover photo: AI-generated illustration of the central black hole, the surrounding accretion disk, and the plasma jet composed of particles accelerated to nearly the speed of light and launched perpendicular to the disk plane – responsible for the intense radio emission. (Credit: MPIfR)