Imaging X-ray Polarimetry Explorer (IXPE), Scientific Discovery, Launch Date

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IXPE (Imaging X-ray Polarimetry Explorer) Latest News

NASA’s IXPE Unlocks X-ray Emission Mystery in Black Hole Jets

What is IXPE?

IXPE (Imaging X-ray Polarimetry Explorer) is a joint mission of NASA and the Italian Space Agency, launched on December 9, 2021.
It is the first satellite capable of measuring the polarisation of X-ray light, a key feature for understanding high-energy astrophysical phenomena.

Blazars are a type of active galactic nuclei (AGN) where a supermassive black hole ejects a relativistic jet of particles oriented directly toward Earth.
BL Lacertae (BL Lac) is a well-known blazar and among the first discovered. It is located in the Lacerta constellation.
It is distinguished by its high variability and intense electromagnetic emissions, making it a suitable candidate for polarisation studies.

The mission aimed to solve the long-standing mystery of how X-rays are generated in black hole jets.
Two competing theories existed:
- Proton-based models (would result in high X-ray polarization).
- Electron-based models (would result in low X-ray polarization).
IXPE’s observations found that the X-rays emitted from BL Lac’s jets were only weakly polarized (no more than 7.6%).
Simultaneously, the optical light was highly polarised (as high as 47.5%, the highest ever recorded for a blazar).
This clear contrast confirmed that the X-rays are not generated by protons, but rather through electron-photon interactions.

The phenomenon responsible is Compton Scattering, where high-speed electrons scatter infrared photons, boosting them to X-ray energies.
This interaction provides a direct link between relativistic electron activity and X-ray generation in extreme environments.