NASA’s planet-hunting satellite observes a smaller object inside a pair of black holes for the 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 proposed by astronomers from the University of Turku in Finland. A new study shows that satellite observations made in 2021 have revealed the pair’s smaller black hole for the first time.

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

The Transiting Exoplanet Survey Satellite (TESS) is designed to discover thousands of exoplanets in orbit around the brightest dwarf stars in the sky. TESS finds planets from small, rocky worlds to giant planets, showing the diversity of planets in our galaxy. So far, it has found 410 confirmed exoplanets, or “new worlds,” that orbit stars other than the Sun.

In 2021, TESS spent several weeks studying a different kind of system, a distant galaxy called OJ 287. Researchers found indirect evidence that the very massive black hole in OJ 287 is orbiting a supermassive black hole 100 times its size.

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

This kind of event has never been observed in OJ287 before, but researcher Pauli Pihajoki from the University of Turku in Finland predicted this event in his doctoral dissertation back in 2014. According to his dissertation, another flare was expected in late 2021, and the object was several satellites and telescopes focused at the time.

The TESS satellite detected the expected eruption on November 12, 2021 at 2:00 GMT, and the observations were recently published in a study in The Astrophysical 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 scientists from Turku 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 aimed at the same target.

In addition, a large international collaboration led by Staszko Zola of the Jagiellonian University in Krakow, Poland, detected the same event using telescopes in different parts of the Earth, so it was always nighttime at at least one of the telescope sites. the whole day. Additionally, a group from Boston University in the US led by Svetlana Jorstad and other observers confirmed the discovery by studying the polarization of light before and after the eruption.

In a new study that combines all previous observations, Professor Mauri Valtonen and his research team from the University of Turku have shown that the 12-hour flash of light came from a smaller black hole in and around the orbit. This study was published in The Astrophysical Journal Letters.

The rapid flash 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 stream of gas.

The jet from the smaller black hole is then brighter than the jet from the larger black hole for about 12 hours. This makes the color of OJ287 less reddish or yellow, instead of the normal red. After the explosion, the red color will return. The yellow color shows that we see light from the smaller black hole for 12 hours. The same results can be derived from other properties of the light emitted from OJ287 during the same time period.

“Therefore, we can now say that we have ‘seen’ an orbiting black hole for the first time, just as we can say that TESS has seen planets orbiting other stars. And as with planets, it is extremely difficult to get a direct image of a smaller black hole. In fact, given the great distance of OJ 287, approaching four billion light-years, it will likely take a very long time for our observational methods to develop enough to even take a picture . a bigger black hole,” says Professor Valtonen.

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