A team of astronomers has captured the most detailed image yet of a powerful jet blasting out from the supermassive black hole at the heart of blazar OJ 287, and what they found is extraordinary. The jet is severely bent, revealing compelling evidence that this object, located about four billion light-years away, could be part of the most extreme binary black hole system ever detected.
A Blazar Unlike Any Other
A blazar is a type of quasar viewed almost directly along its jet, making it appear brighter than most other cosmic objects. Quasars themselves are the luminous cores of galaxies, where supermassive black holes feed on vast amounts of surrounding matter. This matter forms an accretion disk so dense and hot that it shines across the universe, while magnetic fields channel charged particles into jets traveling at nearly the speed of light.
OJ 287, however, defies expectations. Astronomers have been monitoring its fluctuating brightness for around 150 years, uncovering two distinct cycles: one lasting roughly 60 years and another repeating every 12 years. Scientists believe the shorter cycle is caused by a second black hole, roughly 150 million times the mass of the sun, orbiting an even larger primary black hole estimated to weigh in at a staggering 18.35 billion solar masses.
Every 12 years, the smaller black hole plunges through the accretion disk of its massive companion. This dramatic interaction briefly transforms OJ 287 into a double quasar, as the secondary black hole forms its own temporary accretion disk and jet.
The Bent Jet and What it Reveals
The most recent breakthrough came through an unprecedented radio observation of OJ 287, carried out by a network of telescopes including the Very Long Baseline Array (VLBA) in the United States and the Russian RadioAstron satellite. By linking these instruments between 2014 and 2017, astronomers effectively created a virtual telescope five times the diameter of Earth, allowing them to resolve a region just one-third of a light-year across.
The resulting image revealed that the jet is not straight but bent at three distinct points. According to lead researcher Efthalia Traianou of Heidelberg University, “We have never before observed a structure in the OJ 287 galaxy at the level of details seen in the new image.” The team also discovered that the jet’s orientation shifts by about 30 degrees close to its origin, likely due to the gravitational influence of the second black hole.
This gravitational tug could explain the jet’s unusual precession and even its violent outbursts. A shock wave detected within the jet was found to emit an intense stream of gamma rays, recorded by NASA’s Fermi Space Telescope and the Swift mission. Some portions of the jet appear to radiate at an astonishing 10 trillion degrees Celsius, although scientists attribute this to relativistic beaming, where objects moving near light speed appear far brighter and hotter from our vantage point.
A Gateway To Gravitational Wave Research
As Traianou explained, “Its special properties make the galaxy an ideal candidate for further research into merging black holes and the associated gravitational waves.” While the two massive black holes in OJ 287 are expected to merge eventually, the event is not imminent.
In the meantime, their slow inspiral is likely generating faint, long-wavelength gravitational waves that are beyond the reach of current detectors. Instead, astronomers are turning to pulsar timing arrays, which monitor the precise radio signals of pulsars to detect tiny disturbances caused by passing gravitational waves.
The European Space Agency’s Laser Interferometer Space Antenna (LISA), expected to launch in the mid-2030s, could enable scientists to directly detect the merger of supermassive black holes such as those in OJ 287.