GUWAHATI: In a groundbreaking achievement, scientists from the Indian Institute of Technology Guwahati (IIT Guwahati) and the UR Rao Satellite Centre, part of the Indian Space Research Organisation (ISRO) in Bengaluru, have successfully detected polarized emissions from a black hole source situated beyond our Milky Way galaxy. This groundbreaking discovery utilizes a sophisticated technique known as X-ray polarimetry.
The focal point of this study is the binary star system, Large Magellanic Cloud X-3 (LMC X-3), housing a black hole and a massive, hotter star surpassing the Sun in size. Positioned in a satellite galaxy nearly 200,000 light-years away from Earth, LMC X-3 has been under observation since its identification in 1971.
One of the challenges in astrophysics has been understanding the polarization properties of X-rays emitted by highly energetic objects, such as stellar mass black holes in the universe. To address this gap in knowledge, the researchers employed X-ray polarimetry, a distinctive observational technique capable of identifying the origin of radiation near black holes.
Professor Santabrata Das from the Department of Physics at IIT Guwahati emphasized the significance of X-ray polarimetry in this research. He explained, "LMC X-3 emits X-rays 10,000 times more powerful than those from the Sun. When these X-rays interact with the material around black holes, it changes the polarization characteristics, helping us understand how matter is drawn towards black holes in the presence of intense gravitational forces."
The study focused on LMC X-3, utilizing data from The Imaging X-ray Polarimetry Explorer (IXPE), NASA's pioneering mission designed to study the polarization of X-rays from celestial objects. Simultaneously, the researchers made use of the broad-band coverage provided by the Neutron Star Interior Composition Explorer (NICER) Mission and the Nuclear Spectroscopic Telescope Array (NuSTAR) Mission to constrain the spin of LMC X-3.
Anuj Nandi, a Scientist at the U. R. Rao Satellite Centre (URSC), ISRO, highlighted the implications of their findings, stating, "Intense gravitational fields can cause emitted light from black holes to become polarized. Our observations indicate that LMC X-3 likely harbors a black hole with a low rotation rate, surrounded by a slim disc structure that gives rise to polarized emissions."
This breakthrough opens a new avenue for investigating and understanding the nature of astrophysical black hole sources, offering unprecedented insights into the enigmatic world beyond our Milky Way.