Astrophysicists had 2 completing possible descriptions for X-rays form extremely relativistic jets, one including protons and one including electrons.

Each of these systems would have a various signature in the polarization of X-ray light.

Polarization is a home of light that explains the typical instructions of the electro-magnetic waves that comprise light.

If the X-rays in a great void’s jets are extremely polarized, that would imply that the X-rays are produced by protons gyrating in the electromagnetic field of the jet or protons communicating with jet’s photons.

If the X-rays have a lower polarization degree, it would recommend that electron-photons interactions cause X-ray production.

IXPE is the only satellite flying today that can make such a polarization measurement.

“This was among the most significant secrets about supermassive great void jets” stated Dr. Iván Agudo, an astronomer at the Instituto de Astrofísica de Andalucía– CSIC.

“And IXPE, with the aid of a variety of supporting ground-based telescopes, lastly supplied us with the tools to resolve it.”

Astronomers discovered that electrons need to be the perpetrators through a procedure called Compton scattering.

Understood as the Compton impact, this procedure takes place when a photon loses or acquires energy after connecting with a charged particle, normally an electron.

Within jets from supermassive great voids, electrons move near the speed of light.

IXPE assisted the astronomers discover that, when it comes to a blazar jet, the electrons have enough energy to spread photons of infrared illuminate to X-ray wavelengths.

BL Lacertae is among the very first blazars ever found, initially believed to be a variable star in the constellation of Lacerta.

IXPE observed BL Lacertae in November 2023 for 7 days together with a number of ground-based telescopes determining optical and radio polarization at the exact same time.

Coincidentally, throughout the X-ray polarization observations, the optical polarization of BL Lacertae reached a high number: 47.5%.

“This was not just the most polarized BL Lacertae has actually remained in the previous 30 years, this is the most polarized any blazar has actually ever been observed,” stated Dr. Ioannis Liodakis, an astrophysicist at the Institute of Astrophysics– FORTH.

The scientists discovered the X-rays were far less polarized than the optical light.

They were unable to determine a strong polarization signal and identified that the X-rays can not be more polarized than 7.6%.

This showed that electrons engaging with photons, by means of the Compton impact, should discuss the X-rays.

“The truth that optical polarization was so much greater than in the X-rays can just be described by Compton scattering”, stated IXPE task researcher Dr. Steven Ehlert, an astronomer at the Marshall Space Flight.

“IXPE has actually handled to resolve another great void secret” stated Dr. Enrico Costa, an astrophysicist at the Istituto di Astrofísica e Planetologia Spaziali of the Istituto Nazionale di Astrofísica.

“IXPE’s polarized X-ray vision has actually resolved numerous long-term secrets, and this is among the most crucial.

“In some other cases, IXPE outcomes have actually challenged combined viewpoints and opened brand-new enigmas, however this is how science works and, for sure, IXPE is doing excellent science.”

The findings appear in the Astrophysical Journal Letters

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Ivan Agudo et al2025. High optical to X-ray polarization ratio exposes Compton scattering in BL Lacertae’s jet. ApJLin press; doi: 10.3847/ 2041-8213/ adc572