X-ray Polarisation in Extragalactic Black Hole Source

• 17 Nov 2023

Scientists from the Indian Institute of Technology Guwahati (IIT-G) and ISRO have recently made a groundbreaking discovery by detecting X-ray polarisation in an extragalactic black hole source.

• This development, achieved through X-ray polarimetry, promises to provide new insights into the nature of astrophysical black hole sources.

Key Points

• Pioneering Observation: IIT-G and UR Rao Satellite Centre (URSC), ISRO researchers have identified polarised emissions from a black hole source beyond the Milky Way.
• This marks the first instance of detecting polarised X-rays from such a source using X-ray polarimetry.
• Significance of X-Ray Polarimetry: X-Ray polarimetry emerges as a unique observational technique, offering a pathway to unravel the accreting nature of black hole sources.
• The technique involves analysing polarisation characteristics, such as degree and angle, when X-rays emitted by highly energetic objects like black holes interact with surrounding material.
• Understanding Gravitational Forces: Prof of IIT-G's physics department explains that X-rays from the black hole source LMC X-3, situated in the Large Magellanic Cloud, undergo changes in polarisation characteristics as they interact with surrounding matter.
• This phenomenon aids in comprehending how matter is drawn toward black holes under intense gravitational forces.
• LMC X-3 Overview: LMC X-3 is a binary star system comprising a black hole and a more massive, hotter "normal" star than the Sun. Located in a Milky Way satellite galaxy, around 200,000 light years from Earth, the system has been observed since 1971.
• The researchers highlight a prior gap in understanding the polarisation properties of X-rays emitted by such energetic objects.