Adapted from the University of Alberta press release
This graphic features an artist's impression of the extraordinarily close stellar pairing, known as X9. Photo credit: National Aeronautics and Space Administration.
Astronomers from the University of Alberta have found evidence of a star that orbits around a black hole every 28 minutes. This could be the tightest orbital dance ever seen by a black hole and a companion star.
The close-in stellar couple, or binary, is located in the globular cluster 47 Tucanae, a dense cluster of stars in our galaxy about 14,800 light years away from Earth.
Arash Bahramian, former PhD student, and Craig Heinke, associate professor in the Department of Physics, led the international team investigating the phenomenon. The discovery was made using data from NASA’s Chandra X-ray Observatory as well as NASA’s NuSTAR and the Australia Telescope Compact Array. Intensive simulations run on Alberta’s Rapid Access Cloud verified the unique nature of this star system.
“This white dwarf is so close to the black hole that material is being pulled away from the star and dumped onto a disk of matter around the black hole before falling in,” said Bahramian, lead author on the study. “Luckily for this star, we don’t think it will follow this path into oblivion, but instead will stay in orbit.”
New Chandra data of this system, known as X9, showed that it changes in X-ray brightness in the same manner every 28 minutes, which is likely the length of time it takes the companion star to make one complete orbit around the black hole. The Chandra data also showed evidence for large amounts of oxygen in the system. Using the Rapid Access Cloud (operated by Cybera, Alberta’s not-for-profit technology accelerator), astronomers at the University of Alberta were able to make the case that X9 contains a white dwarf star that is orbiting a black hole.
Assistant Professor of Physics Gregory Sivakoff, who also participated in the study, notes, “We’ve also considered an alternative explanation, where a rapidly rotating neutron star, instead of a black hole, is tearing material from a nearby white dwarf. However, since known examples of such systems have different properties from X9, we think X9 is much more likely to contain a black hole. We’ll be keeping our eyes on X9 and other binary stars like it to test these alternative hypotheses."
The paper, “The ultracompact nature of the black hole candidate X-ray binary 47 Tuc X9”, was published in Monthly Notices of the Royal Astronomical Society in 2017.
For more details on the scientific finding, see the University of Alberta press release.
About NASA’s Chandra X-ray Observatory
NASA's Chandra X-ray Observatory is a telescope specially designed to detect X-ray emission from very hot regions of the Universe such as exploded stars, clusters of galaxies, and matter around black holes. Because X-rays are absorbed by Earth's atmosphere, Chandra must orbit above it, up to an altitude of 139,000 km (86,500 mi) in space. The Smithsonian's Astrophysical Observatory in Cambridge, MA, hosts the Chandra X-ray Center which operates the satellite, processes the data, and distributes it to scientists around the world for analysis.
Cybera is funded by the Government of Alberta and members to accelerate the adoption of advanced technology in the province. In one of its core roles, Cybera manages CyberaNet, the ultra high-speed broadband network that connects Alberta’s educators and innovators to an international system of research networks. Over 650,000 Albertans now connect to CyberaNet.
About the Rapid Access Cloud
The Alberta-based Rapid Access Cloud is funded by the Government of Alberta to:
- Help researchers utilize cloud computing environments for testing, analysis and experimentation
- Give Albertans a competitive advantage by offering a staging ground to test their ideas for cloud-based services, before moving to a commercial cloud platform
- Provide a learning environment for people to explore the possibilities and benefits of cloud computing