Blazar bl lacertae is a supermassive black hole surrounded by bright disks and a planet-oriented jet provides scientists with a unique opportunity to answer a long-standing question: How to generate X-rays in such extreme environments?

NASA's IXPE (Imaging X-ray Polarization Explorer) works with radio and optical telescopes to find the answer. The results (a preprint available here) will be published in the journal Astrophysics Journal, suggesting that the interaction between fast-moving electrons and photon particles (called photons) must result in this X-ray emission.

Scientists have two competing possible explanations for X-rays, one involving protons and the other involving electrons. Each of these mechanisms has different characteristics in the polarization of X-ray light. Polarization is a characteristic of light, describing the average direction of the electromagnetic waves that make up light.

If the X-rays in the jet of a black hole are highly polarized, it means that the X-ray is produced by protons that rotate in the jet or in the magnetic field of the proton, or interact with the photons of the jet. If the X-ray has a lower polarization, it is indicated that electron interactions will cause X-ray generation.

Launched on December 9, 2021, IXPE is the only satellite flight today that can perform such polarization measurements.

"This is one of the biggest mysteries of supermass black hole jets," said Iván Agudo, the study's lead author, who is also an astronomer at the Spanish CSIC. “And IXPE, with the help of many supporting ground telescopes, finally provided us with tools to solve it.”

Astronomers have found that electrons must be the culprit through a process called Compton scattering. Compton scattering (or Compton effect) occurs when a photon interacts with charged particles (usually electrons). In the jet of a super black hole, electrons move near the speed of light. IXPE helps scientists understand that in the case of large jets, electrons have enough energy to scatter infrared photons to X-ray wavelengths.

Bl lacertae (Bl lac for short) is the first ever discovered marijuana, originally thought to be a variable star in the Lacerta constellation. IXPE observed BL LAC for 7 days at the end of November 2023, along with several ground telescopes, which simultaneously measure optical and radio polarization. Although IXPE has observed Bllac in the past, this observation is special. Coincidentally, during the X-ray polarization observations, the optical polarization of the BL LAC reached a very high number: 47.5%.

"This is not only the most polarized BL LAC in the last 30 years, but also the polarization of any large Blazar ever observed!" said Ioannis Liodakis, one of the lead authors of the study and one of the leading authors of the Institute of Astrophysics, in Greece, Ioannis Liodakis.

IXPE found that X-rays are much worse than optical lamps. The team was unable to measure powerful polarization signals and determined that the X-rays could not be more polarized than 7.6%. This proves that electrons interacting with photons through the Compton effect must interpret X-rays.

"The fact that optical polarization is much higher than in X-rays can be explained," said Steven Ehlert, a project scientist at IXPE and astronomer at the Marshall Space Flight Center.

"Ixpe managed to solve another black hole mystery," said Enrico Costa.,,,,, Rome astrophysicists in Istituto di Astrofísica e astrologia spranetologia s spaziali isituto nazionale di Astrofísica. Costa is one of the scientists who conceived the experiment and presented it to NASA 10 years ago, under the leadership of Martin Weisskopf, the first principal investigator at IXPE. “The polarized X-ray field of view of IXPE has solved several lasting mysteries, one of the most important ones. In other cases, the IXPE results challenged the merger opinions and opened up new mysteries, but that’s how science works, and IXPE is doing well, to be sure.”

What's next for Blazar research?

“One of the things we have to do is try to find as many of them as possible,” Ellert said. “As time goes by, the Blazars have changed a lot, full of surprises.”

More information about ixpe

IXPE continues to provide unprecedented data that will make celestial objects throughout the universe a breakthrough discovery, and is a flight agent jointly by NASA and the Italian Space Agency, with partners and scientific collaborators in 12 countries. IXPE is led by the Marshall Space Flight Center of NASA in Huntsville, Alabama. Bae Systems, Inc. Headquartered in Falls Church, Virginia, it manages spacecraft operations with the University of Colorado’s Boulder Atmospheric and Space Physics Laboratory. Learn more about IXPE's ongoing tasks here:

Elizabeth Landau
NASA Headquarters
elizabeth.r.landau@nasa.gov
202-358-0845

Lane figueroa
Marshall Space Flight Center, Huntsville, Alabama.
lane.e.figueroa@nasa.gov
256.544.0034