NASA’s planet-hunting satellite directly observes smaller object in pair of black holes for first time

Several international research groups have already confirmed the theory that there are two black holes at the center of the distant galaxy OJ 287, first suggested by astronomers at the University of Turku, Finland. A new study shows that satellite observations conducted in 2021 revealed the smaller black hole of the pair for the first time.

In 2021, NASA’s exoplanet-hunting satellite was pointed at the OJ 287 galaxy to help astronomers confirm the theory initially proposed by researchers at the University of Turku, Finland, that there are two holes blacks at the center of the galaxy.

The Transiting Exoplanet Survey Satellite (TESS) is designed to discover thousands of exoplanets orbiting the brightest dwarf stars in the sky. TESS discovers planets ranging from small rocky worlds to giant planets, showcasing the diversity of planets in our galaxy. So far, the team has discovered 410 confirmed exoplanets or “new worlds” orbiting stars other than the sun.

In 2021, TESS spent several weeks studying a different type of system, a distant galaxy called OJ 287. Researchers found indirect evidence that a very massive black hole in OJ 287 orbits a giant black hole 100 times her size.

To verify the existence of the smaller black hole, TESS monitored the brightness of the primary black hole and its associated jet. Direct observation of the smaller black hole orbiting the larger one is very difficult, but its presence was revealed to researchers by a sudden burst of brightness.

This type of event had never been observed before in OJ287, but researcher Pauli Pihajoki from the University of Turku in Finland had already predicted this event in his doctoral thesis in 2014. According to his thesis, the next eruption should have place at the end of the period. 2021, and several satellites and telescopes were then focused on the object.

The TESS satellite detected the expected eruption on November 12, 2021 at 02:00 GMT, and the observations were recently published in a study in The Astrophysics Journal by Shubham Kishore, Alok Gupta (Aryabhatta Research Institute of Observational Sciences, India) and Paul Wiita (The College of New Jersey, USA).

The event lasted only 12 hours. This short duration shows that it is very difficult to find a flash of great brightness unless its timing is known in advance. In this case, the theory of the Turku researchers turned out to be correct and TESS was directed to OJ 287 at the right time. The discovery was also confirmed by NASA’s Swift telescope, which was also pointed at the same target.

Additionally, a large international collaboration led by Staszek Zola of the Jagiellonian University in Krakow, Poland, detected the same event using telescopes in different parts of the Earth, so that it was always dark at least at l one of the telescope locations. all day. Additionally, a group from Boston University, US, led by Svetlana Jorstad and other observers, confirmed the finding by studying the polarization of light before and after the eruption.

In a new study combining all previous observations, Professor Mauri Valtonen and his research team from the University of Turku showed that the 12-hour burst of light came from the smaller orbiting black hole and its surroundings. This study was published in Letters from the astrophysical journal.

The rapid burst of brightness occurs when the smaller black hole “swallows” a large slice of the accretion disk surrounding the larger black hole, turning it into an outward jet of gas.

The jet from the smaller black hole is then brighter than that from the larger black hole for about 12 hours. This makes the color of OJ287 less reddish, or yellow, instead of normal red. After the start, the red color returns. The yellow color indicates that over a 12 hour period we see light from the smaller black hole. The same results can be inferred from other characteristics of the light emitted by OJ287 during the same period.

“Therefore, we can now say that we ‘saw’ an orbiting black hole for the first time, in the same way that we can say that TESS saw planets orbiting other stars. And just like for planets, it is extremely difficult to obtain a direct image of the smaller black hole. In fact, due to the great distance of OJ 287, which is close to four billion light years, it will probably take a long time. before our observation methods are developed enough to capture even an image of this largest black hole,” explains Professor Valtonen.

“However, the smaller black hole may soon reveal its existence in other ways, as it is expected to emit gravitational waves on the order of nanohertz. OJ 287’s gravitational waves should be detectable in the coming years by maturing pulsar timing networks,” says A. Gopakumar of the Tata Institute of Fundamental Research in India.