For the first time in 52 years, scientists have achieved a major breakthrough in space science! Four researchers from the Indian Space Research Organisation (ISRO) and the Indian Institute of Technology (IIT) Guwahati have detected polarised emissions from a black hole source that exists beyond our Milky Way Galaxy using a technique called X-ray polarimetry.
This feat has been achieved for the first time since the discovery of the Large Magellanic Cloud X-3 (LMC X3) star system in 1971, which is binary in nature and consists of a black hole and a normal star that is much hotter, bigger, and more massive than the Sun, as per a report by The New Indian Express.
The LMC X3 is located in a satellite galaxy of our Milky Way, nearly 2,00,000 light-years away from Earth. For over half a century the star system was observed by many satellites but there was a gap in understanding the polarisation properties of X-rays emitted by highly energetic objects like stellar mass black holes in the universe.
Now, the X-ray polarimetry method used by Indian scientists has enabled the investigation and understanding of the nature of astrophysical black hole sources. The researchers studied LMC X-3 using the Imaging X-ray Polarimetry Explorer (IXPE), the first mission of NASA to study the polarisation of X-rays from celestial objects. They also made use of the simultaneous broad-band coverage of the Neutron Star Interior Composition Explorer (NICER) Mission and Nuclear Spectroscopic Telescope Array (NuSTAR) Mission to constrain the spin of LMC X-3.
The research was published in the Monthly Notices of the Royal Astronomical Society: Letters and was funded by the Science and Engineering Research Board (SERB), Department of Science and Technology, India. The team was led by Santabrata Das, Department of Physics, IIT Guwahati, and Dr Anuj Nandi, Scientist, UR Rao Satellite Centre (URSC), ISRO. The team also included research scholars Seshadri Majumder (IIT Guwahati) and Ankur Kushwaha (URSC).
Speaking on the research, Professor Santabrata Das said, “X-ray polarimetry is a unique observational technique to identify where radiation comes from near black holes. LMC X-3 emits X-rays that are 10,000 times more powerful than those from the Sun. When these X-rays interact with the material around black holes, specifically when they scatter, it changes the polarisation characteristics, that is degree and angle. This helps in understanding how matter is drawn toward black holes in the presence of intense gravitational forces.”
Dr Nandi further explained that the intense gravitational fields can cause the emitted light from black holes to become polarised. “Our observations indicate that LMC X-3 likely harbours a black hole with a low rotation rate, surrounded by a slim disc structure that gives rise to the polarised emissions,” he added, as per The New Indian Express.