Particle accelerators in the sky: NASA's IXPE explores 'microquasar' mechanism

NASA's IXPE mission uses the microquasar SS433 as a case study to reveal the aligned magnetic fields in its jets, transforming our understanding of particle acceleration in black holes. The powerful gravitational fields of black holes can swallow up entire planets' matter - often so violently that they expel streams of particles approaching the speed of light in jets. Scientists know that these high-speed jets accelerate these particles, known as cosmic rays, but little is known about the process.

This composite view of the Manatee Nebula captures jets from SS433, a black hole that is devouring material from the remnants of the supernova that created it. New research using data from the IXPE spacecraft, specifically through the study of the microquasar SS433, sheds light on the phenomenon of particle acceleration by black holes. The work reveals that magnetic fields within jets are consistent with their motion, contradicting previous theories and enhancing our understanding of this cosmic phenomenon.

The latest discovery, made by researchers using data from NASA's IXPE (X-ray Polar Imaging Explorer) spacecraft, gives scientists new clues about how particle acceleration occurs in such extreme environments. The observations come from a "microquasar," a system composed of a black hole siphoning material from a companion star.

A closer look at SS433

This microquasar (Stephenson and Sanduleak 433, referred to as SS433) is located in the center of the Aquila supernova remnant W50, about 18,000 light-years away from the Earth. SS433's powerful jets, which distort the shape of the remnant and earn it the nickname "The Manatee Nebula," travel at about 26 percent of the speed of light, or more than 48,000 miles per second. SS433 was discovered in the late 1970s and was the first microquasar ever discovered.

IXPE's three onboard telescopes measure a special property of X-ray light called polarization, which tells scientists how electromagnetic waves are organized and arranged at X-ray frequencies. X-ray polarization helps researchers understand the physical processes that occur in extreme regions of the universe, such as the environment around black holes, and how particles are accelerated in these regions.

The radio waves emitted by the remnants are blue-green, while the X-rays synthesized by IXPE, XMM-Newton and Chandra are dominated by bright blue-violet and pink-white tones, and the infrared data has a red background. The black hole ejects two jets of material in opposite directions at nearly the speed of light, distorting the shape of the remnants. The jet becomes bright about 100 light-years away from the black hole, and particles are accelerated to very high energies by impacts inside the jet. The IXPE data shows that magnetic fields, which play a key role in particle acceleration, are aligned parallel to the jets - helping us understand how astrophysical jets accelerate these particles to high energies.

Breakthrough discoveries and future implications

IXPE spent 18 days in April and May 2023 studying one such acceleration point in the east lobe of SS433, where high-energy electrons spiraling in a magnetic field create radiation -- a process known as synchrotron radiation.

"The IXPE data show that the magnetic field near the acceleration region points in the direction the jet is moving," said astrophysicist Philip Kaaret of NASA's Marshall Space Flight Center in Huntsville, Alabama, principal investigator for the IXPE mission and lead author of a new paper on the findings on SS433. "The high levels of polarization seen with IXPE suggest that the magnetic fields are ordered, with at least half of them aligned in the same direction," he said.

The discovery was unexpected, he said. Researchers have long thought that interactions between the jets and the interstellar medium (the environment of gas and dust between stars) likely create shocks that cause magnetic field disturbances.