The XL-Calibur balloon telescope captured precise X-ray polarization data from the Cygnus X-1 black hole, offering new insight into superheated matter. It also observed the Crab pulsar and readies for a 2027 Antarctica flight.
A high-altitude telescope riding beneath a giant balloon has given scientists their clearest look yet at the extreme environment around a black hole. During a 2024 flight across the northern hemisphere, researchers used the XL-Calibur telescope to study Cygnus X-1, one of the brightest and most mysterious black hole systems in our galaxy. The telescope’s measurements captured how X-rays near the black hole are polarized—an essential clue to understanding the superheated gas swirling just outside its event horizon.
Peering Into the Chaotic Edge of a Black Hole
Unlike ordinary telescopes, XL-Calibur is built to detect the orientation of X-ray light. This helps scientists trace the motion, temperature, and structure of matter spinning at incredible speeds around black holes. The new analysis, published in The Astrophysical Journal, provides the most precise measurement yet of Cygnus X-1’s hard X-ray polarization. These results will help astrophysicists test advanced simulations that model how black holes feed on nearby material and eject vast amounts of energy.
A Record-Setting Balloon Flight and What Comes Next
Launched from Sweden and landing in Canada, the 2024 mission also measured the iconic Crab pulsar, achieving several engineering breakthroughs for future flights. The team now plans a new XL-Calibur mission from Antarctica in 2027, aiming to expand observations to more black holes and neutron stars. Combined with data from NASA’s IXPE satellite, these efforts may finally answer long-standing questions about how black holes bend light, shape matter, and power some of the universe’s most energetic events. The study is published in The Astrophysical Journal.