Today's Editorial

Today's Editorial - 02 January 2024

Meet ISRO’s new X-ray eye in the sky

News Excerpt: 

The successful launch of the X-ray Polarimeter Satellite (XPoSat) by the Indian Space Research Organisation (ISRO) ushers in a new era of astronomical exploration. This innovative payload, entirely indigenous in design and fabrication, carries the promise of unlocking profound cosmic secrets through its cutting-edge instrument, the Indian X-ray Polarimeter (POLIX).

Mission Objective:

The primary goal of XPoSat is to study the polarization of X-rays coming from bright celestial sources in the medium frequency band. This is achieved through two scientific payloads: POLIX and XSPECT, developed by institutions in Bengaluru.

Payloads on XPoSat:

  • POLIX: World's first instrument operating in the 8 to 30 keV energy band. It includes a collimator and four X-ray proportional counter detectors to observe astronomical sources, particularly those emitting polarized X-rays.
  • XSPECT: Designed for fast timing and high spectroscopic resolution in the 0.8-15 keV energy band. It observes various sources such as X-ray pulsars, black hole binaries, neutron stars, AGNs, and magnetars.
  • Significance of XPoSat: XPoSat will be a game-changer in enabling X-ray polarization measurements from bright sources, specifically in the medium energy band (8-30 keV) which has not been attempted previously. Studying polarized X-rays from sources like magnetars, black holes, and neutron stars can provide insights into radiation nature and the processes involved in their generation. The invaluable data collected by XPoSat holds the potential to reshape our understanding of pulsars, black holes, and other enigmatic cosmic phenomena, pushing the boundaries of astrophysical knowledge. 
  • Importance of X-ray Polarization Studies: X-rays when emitted by celestial objects get polarized due to various reasons, such as interactions with strong magnetic fields or materials around black holes. Studying polarized X-rays helps understand these phenomena. POLIX aims to measure the degree and angle of polarization of X-ray photons from environments surrounding cosmic entities, aiding in understanding celestial bodies better. 
  • Comparison with Global X-ray Missions: Few missions worldwide have focused on X-ray polarization measurements. NASA's IXPE operates in the soft X-ray band (2 to 8 keV), while XPoSat's POLIX extends observations to the medium X-ray band (8 to 30 keV), complementing IXPE's work.

The Science Behind X-ray Polarimetry:

X-ray polarization is akin to deciphering the orientation of electric fields within these electromagnetic waves. X-rays, like visible light, are electromagnetic waves. Their electric field variations depend on the movement of the electric charges generating these waves. Much like sunlight transformed by reflection or scattering, celestial objects with colossal magnetic fields, such as pulsars and regions around black holes, emit polarized X-rays. Measuring this polarization unveils the elusive secrets of their magnetic field directions and other intriguing phenomena.  In certain scenarios, such as around celestial objects with immense magnetic fields like pulsars and black holes, these X-rays become polarized due to the gyrating motion of electrons along magnetic field lines. Measuring this polarization provides astronomers with invaluable insights into the orientation of magnetic fields within these cosmic entities.


Crafting Precision in X-ray Polarization Measurement, POLIX represents a significant leap in X-ray polarimetry. Despite its relatively compact size – approximately half a meter in dimensions and weighing nearly 200 kilograms – POLIX embodies sophisticated technology for precise measurement of polarized X-rays. Took over 15 years at the Raman Research Institute (RRI) in Bangalore to develop this device. The instrument's innovative design, conceived by Biswajit Paul, features a cubical cylinder shape with a core comprising a beryllium disc. Strategically positioned detectors surrounding this metallic core capture and analyze the scattered X-rays, allowing POLIX to determine the polarization of the incoming X-ray photons.

Technical features of POLIX:

POLIX's detectors, aligned along the instrument's walls, are instrumental in collecting X-rays post-scattering from the beryllium disc. This unique setup enables the instrument to discern the directionality of the polarized X-rays, akin to how sunlight becomes polarized after interaction with Earth's atmosphere. The choice of beryllium, despite lithium being an ideal option due to its properties, was made considering practical handling reasons. POLIX's capability to probe lower energy X-rays compared to existing instruments positions it as a significant asset in studying pulsars, black holes, and other cosmic phenomena emitting X-rays.

Role in Astrophysical Exploration:

XPoSat's POLIX serves as a complementary asset to global efforts in X-ray polarimetry. While previous attempts with balloon-borne instruments paved the way, recent endeavors like NASA's Imaging X-ray Polarimetry Explorer (IXPE) highlight the growing interest in this field. POLIX's unique capabilities promise to fill crucial gaps in understanding polarized X-rays from cosmic sources, offering a new lens to observe and decode celestial mysteries.


The successful launch of XPoSat marks a significant leap for Indian astronomers, promising unparalleled opportunities to delve into the enigmatic realms of the universe. With its mission set to unravel the mysteries concealed within polarized X-rays from celestial sources, XPoSat is poised to redefine our understanding of cosmic phenomena and unveil new frontiers in astrophysics.


Mains PYQ:

Q. What is India’s plan to have its own space station and how will it benefit our space programme? (UPSC 2019)

Q. India has achieved remarkable successes in unmanned space missions including the Chandrayaan and Mars Orbiter Mission, but has not ventured into manned space missions, both in terms of technology and logistics? Explain critically. (UPSC 2017)

Q. Discuss India’s achievements in the field of Space Science and Technology. How the application of this technology has helped India in its socio-economic development? (UPSC 2016)

Book A Free Counseling Session