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ISRO Launches X-ray Polarimeter Satellite (XpoSat)


The Indian Space Research Organisation (ISRO) has successfully launched its inaugural X-ray Polarimeter Satellite (XpoSat) to study X-ray polarization and investigate cosmic sources such as Black holes, Neutron stars, and Magnetars. The mission was propelled into Low Earth Orbit via the PSLV-C58 rocket.


GS III: Science and Technology

Dimensions of the Article:

  1. X-ray Polarimeter Satellite (XPoSat)
  2. X-rays and their Study of Celestial Objects

X-ray Polarimeter Satellite (XPoSat):


  • Designed to study X-ray polarization in the medium X-ray band, providing crucial insights into the radiation mechanisms and geometry of celestial sources.

Significance for Astrophysics:

  • Essential for understanding the physics underlying celestial bodies and their radiation processes.

Carries two main payloads:

  • POLIX (Polarimeter Instrument in X-rays):
    • Observes approximately 40 bright astronomical sources.
  • XSPECT (X-ray Spectroscopy and Timing):
    • Studies the electromagnetic spectrum produced by different types of matter.
  • Entirely constructed by two Bengaluru-based institutes—ISRO’s UR Rao Satellite Centre and Raman Research Institute.
  • Development initiated in 2008, with a formal agreement signed with ISRO in 2015.
Global Context:
  • Only the world’s second mission dedicated to X-ray polarization in the medium X-ray band.
  • NASA’s Imaging X-ray Polarimetry Explorer (IXPE), launched in 2021, was the first such mission by a space agency.
National Contribution:
  • Marks India’s third space-based observatory, succeeding the recently launched solar mission Aditya-L1 and AstroSat, launched in 2015.
  • Represents a significant advancement for Indian astronomy and space research.

X-rays and their Study of Celestial Objects:

Nature of X-rays:

  • X-rays are a form of electromagnetic radiation with wavelengths ranging from 0.01 to 10 nanometres.

Electromagnetic Radiation Characteristics:

  • Electromagnetic radiation exhibits characteristics of an electric field and a magnetic field vibrating perpendicular to each other.

Polarization of Electromagnetic Radiation:

  • Polarization refers to the orientation of the electric and magnetic fields as electromagnetic radiation moves through space.

Polarization of X-rays:

  • X-rays can undergo polarization when scattered.
  • Polarized X-rays are also generated when the path of a fast-moving charged particle is altered by a magnetic field.

Measurement and Astronomical Insights:

  • Instruments like POLIX are utilized to measure the polarization of X-rays.
  • This measurement allows astronomers to comprehend the orientation and strength of magnetic fields in celestial objects.


  • Insights into the nature and behavior of celestial phenomena emitting X-rays are gained.
  • Crucial understanding of pulsars, regions around black holes, and other cosmic entities emitting X-rays is achieved through the study of X-ray polarization.

-Source: The Hindu, PIB, Indian Express

February 2024