Unveiling a Century-Old Mystery at the Heart of a Luminous Quasar
A team of international researchers has achieved a milestone in astronomy by capturing direct images of two supermassive black holes in orbit around one another at the core of the quasar OJ287. Quasars are among the brightest objects in the universe, powered by gas and dust spiraling into a supermassive black hole. The new findings, published in the Astrophysical Journal, confirm long-held suspicions that OJ287 harbors not one but two black holes circling each other with a distinctive 12-year orbital rhythm.
OJ287’s startling brightness makes it visible to skilled amateur astronomers using modest equipment, a fact that has aided decades of ongoing observations. The quasar’s regular brightness variations over a 12-year cycle had long suggested a binary black hole system, but only with recent high-resolution radio imaging could scientists resolve the two distinct cores and their dynamic interactions.
From Accidental Discovery to a Precise Image
Historical records trace OJ287 back to the 19th century as researchers photographed the region of the sky where the quasar sits. It was only in 1982 that Aimo Sillanpää, then a master’s student, noticed the recurring 12-year light fluctuations. His work laid the groundwork for the binary black hole hypothesis, which later researchers refined and tested through the decades.
For years, astronomers hoped to observe both black holes simultaneously. The breakthrough arrived thanks to radio-wave imaging capabilities. While NASA’s TESS satellite had detected light from the system on a broader scale, the needed resolution came from radio interferometry—an approach that combines signals from widely separated antennas to produce an image with extraordinary detail. The decisive resolution required was about 100,000 times finer than typical optical observations.
A New Type of Jet and the Wagging Tail of the Smaller Black Hole
The latest study’s comparison of theoretical models with the radio image reveals a striking feature: a jet from the smaller black hole that twists and curves like a rotating garden hose. This “wagging tail” effect results from the smaller hole’s rapid orbital motion around the primary black hole, bending and redirecting the jet as its trajectory evolves over time.
Researchers describe the two black holes by the positions of their jets, which illuminate otherwise invisible regions. The visible jets mark the locations of the black holes themselves, while the gaps between jets correspond to the calm, dark cores that lie beneath. This dual-jet signature provides compelling confirmation of a binary system rather than a single, solitary black hole masquerading as two through complex accretion patterns.
Resolving a 40-Year Puzzle with Radio Astronomy
The image was achieved with a radio telescope network that included the RadioAstron satellite, an instrument once capable of extending radio baselines far beyond Earth’s diameter. Although RadioAstron operated years ago, its data contributed to the high-resolution image that mapped the two distinct black holes in OJ287. In more recent times, ground-based facilities have continued to advance, but the unique clarity achieved in this study marks a watershed moment for observing black-hole binaries in distant quasars.
What This Means for Black-Hole Physics and the Future of Imaging
This direct observation of two black holes in orbit around each other provides critical validation for long-standing theoretical models describing the dynamics of binary black-hole systems. It also opens new avenues for studying how such systems influence the timing and brightness of their host quasars, as well as how their jets interact with surrounding gas and dust. As researchers monitor OJ287 over the coming years, the evolving jet orientations and emission patterns promise to reveal further details about relativistic effects, gravitational interactions, and the ultimate fate of this dramatic cosmic pair.
About the Researchers and the Study
The study’s first author, Mauri Valtonen of the University of Turku, and collaborators from institutions around the world contributed to a multi-decade effort to decode the orbital dynamics of OJ287. The central discovery—two black holes in mutual orbit—emerges from refining models against precise radio images and cross-validating predictions with timing data. As astrophysicists continue to push the boundaries of resolution and sensitivity, more binary systems like OJ287 may be discovered and imaged, deepening our understanding of how supermassive black holes shape the evolution of galaxies.
Journal Reference: Astrophysical Journal (link and DOI provided in the study).
