NASA spots unexpected X-ray polarization in ‘Heartbeat’ black hole, hinting at extreme cosmic winds or rapid plasma jets

A black hole located about 28,000 light-years from Earth is puzzling astronomers with its unusual “heartbeat”, rhythmic pulses in brightness that defy conventional models of black hole behavior.

Using NASA’s Imaging X-ray Polarimetry Explorer (IXPE), scientists observed black hole IGR J17091-3624 for its rhythmic brightening and dimming.

These pulses occur as the black hole feeds on matter from a nearby companion star, heating gas in its accretion disk and the ultra-hot corona that surrounds it.


In April, IXPE measured a surprising 9.1 per cent polarization degree, far higher than predicted by models.

Polarization indicates how aligned X-ray light waves are, and this reading suggests unusual structure or motion in the black hole’s corona.

“The black hole IGR J17091-3624 is an extraordinary source which dims and brightens with the likeness of a heartbeat, and NASA’s IXPE allowed us to measure this unique source in a brand-new way,” said Melissa Ewing in the statement release by NASA on August 12, lead of the study from Newcastle University.

Unusual X-ray signals

The corona is a region of superheated, magnetized plasma near the black hole, reaching temperatures up to 1.8 billion degrees Fahrenheit and producing some of the brightest X-rays in the sky.

Normally, a high polarization degree like this would suggest the corona is viewed edge-on, perfectly aligned with Earth, but other observations of IGR J17091-3624 don’t match that scenario.

To put it simply, the study found that the X-rays emitted by the hot plasma around the black hole, known as the corona, were far more aligned than expected, with a polarization degree of 9.1 percent.

This unusually high alignment challenges existing models, which predicted much lower polarization. It suggests that the corona and surrounding environment behave in ways scientists do not yet fully understand.

Possible explanation

Researchers tested two models to explain the odd readings. One proposes that strong winds of matter rising from the accretion disk scatter X-rays, increasing polarization.

Another suggests the corona itself is shooting out plasma at nearly 20 per cent of the speed of light, with relativistic effects amplifying the observed signal. Both models reproduce the IXPE measurements without requiring a perfectly edge-on view.

What this means for black hole research

The findings, published on May 27 in Monthly Notices of the Royal Astronomical Society, highlight how black holes continue to defy expectations and reveal the complexity of the extreme environments surrounding them.

Future observations of IGR J17091-3624 and similar systems could reshape astronomers’ understanding of black hole growth, matter dynamics, and the fundamental physics governing these cosmic giants.