NASA solves Black Hole Jet mystery with IXPE: Compton scattering confirmed as X-Ray source
NASA’s Imaging X-ray Polarimetry Explorer (IXPE) has solved a long-standing cosmic mystery about how X-rays are generated in the powerful jets of black holes like blazar BL Lacertae. By observing low X-ray polarisation alongside high optical polarisation, the findings point to Compton scattering.
NASA’s IXPE mission has taken a major leap in solving the mystery behind X-ray emissions from blazar BL Lacertae, a type of supermassive black hole shooting energetic jets toward Earth. By studying polarisation, or the alignment of light waves, scientists have now determined that Compton scattering is likely responsible for producing X-rays in these extreme environments.
What IXPE observed
In a focused observation of BL Lacertae in November 2023, scientists recorded an optical polarisation as high as 47.5 per cent—the highest ever measured for a blazar. However, IXPE found the X-ray polarisation to be significantly lower, at just 7.6 per cent. This mismatch strongly indicates that the X-rays are not produced by interactions between photons, but rather by fast-moving electrons scattering photons—a process known as Compton scattering.
A scientific breakthrough
“This was one of the biggest mysteries about supermassive black hole jets,” said Iván Agudo, lead author of the study. The findings mark a milestone for IXPE, which was launched in December 2021 specifically to study X-ray polarisation. Astrophysicist Enrico Costa called it one of IXPE’s most notable achievements.
What’s next?
Project scientist Steven Ehlert emphasised the importance of further studying other blazars, as their emissions change over time. With IXPE’s advanced tools, astronomers are now better equipped to unravel the behaviours of black holes and their powerful jets across the universe.
This breakthrough not only solves a key cosmic mystery but also highlights how far space science has come with cutting-edge technology. NASA’s IXPE mission demonstrates the power of modern instruments in unlocking the universe’s most extreme phenomena. As technology continues to evolve, missions like IXPE are paving the way for deeper exploration into the behaviour of black holes, cosmic jets, and high-energy astrophysics, bringing us closer than ever to understanding the most powerful forces in the cosmos.
ABOUT IXPE
IXPE (Imaging X-ray Polarimetry Explorer) is a joint mission by NASA and the Italian Space Agency, designed to deliver groundbreaking insights into the universe through X-ray polarisation. With scientific collaborators from 12 countries, IXPE continues to unlock new knowledge about celestial objects such as black holes, neutron stars, and cosmic jets. The mission is led by NASA’s Marshall Space Flight Centre in Huntsville, Alabama.