A groundbreaking study led by a team of 32 scientists from 10 countries (Finland, Poland, India, China, USA, Czech Republic, Japan, Germany, Spain, Italy) has achieved the first direct observation of a smaller black hole within a pair, marking a significant milestone in astrophysics.
The research confirms the long-held theory of two black holes at the center of the galaxy OJ 287, located four billion light-years away. This theory, originally proposed by astronomers at the University of Turku, Finland, was corroborated by several international research groups.
In 2021, NASA’s Transiting Exoplanet Survey Satellite (TESS), which typically searches for exoplanets, was redirected to observe OJ 287 to validate this theory. TESS’s observations focused on the brightness variations of the primary black hole and its associated jet, eventually revealing the presence of the smaller orbiting black hole through a sudden burst of brightness.
This burst, unprecedented in previous observations of OJ 287, was predicted by Pauli Pihajoki of the University of Turku in his 2014 doctoral dissertation. The anticipated flare was detected by TESS on November 12, 2021, and the findings were recently published in the Astrophysical Journal Letters.
The study, conducted by Shubham Kishore and Alok C. Gupta from the Aryabhatta Research Institute of Observational Sciences, along with Paul Wiita from The College of New Jersey, confirmed the smaller black hole’s presence. This discovery was further validated by NASA’s Swift telescope and by an international team led by Staszek Zola from Jagiellonian University, Poland, using telescopes positioned globally.
Additionally, researchers from Boston University, led by Svetlana Jorstad, confirmed the findings by analyzing the polarization of light before and after the flare. Combining all observations, Professor Mauri Valtonen and his team from the University of Turku demonstrated that the 12-hour burst originated from the smaller black hole and its surroundings.
The burst occurred when the smaller black hole consumed a significant portion of the accretion disk surrounding the larger black hole, resulting in a brighter jet and altering the color of OJ 287 from red to yellow for the duration of the flare. This “yellow” period indicated the visibility of the smaller black hole.
“Just as TESS has captured planets orbiting stars, we can now say we have ‘seen’ an orbiting black hole,” says Professor Valtonen. “However, capturing an image of the smaller black hole remains a challenge due to OJ 287’s immense distance.”
Future observations might reveal the smaller black hole through nano-Hertz gravitational waves, which are expected to be detectable in the coming years by advanced pulsar timing arrays, according to A. Gopakumar from the Tata Institute of Fundamental Research, Mumbai, India.
Images:
- The burst observed as a sharp flaring in the light curve, with a brightness equivalent to approximately 100 galaxies. (Image credit: Kishore, Gupta, Wiita 2024)
- Illustration of the black holes in orbit, showing the reddish jet of the larger black hole and the yellowish jet of the smaller one, which dominated during the November 12, 2021, observation. (Credit: NASA/JPL-Caltech/R. Hurt (IPAC) & M. Mugrauer (AIU Jena))
