A group of astronomers, including a team from the University of Southampton, have found evidence of a star that whips around a black hole about twice an hour. This may be the tightest orbital dance ever witnessed for a likely black hole and a companion star.

This discovery was made using NASA’s Chandra X-ray Observatory as well as NASA’s NuSTAR and CSIRO’s Australia Telescope Compact Array (ATCA). 



The close-in stellar couple – known as a binary – is located in the globular cluster 47 Tucanae, a dense cluster of stars in our galaxy about 14,800 light years from Earth. 

While astronomers have observed this binary for many years, it wasn’t until 2015 that radio observations with the ATCA revealed the pair likely contains a black hole pulling material from a companion star called a white dwarf, a low-mass star that has exhausted most or all of its nuclear fuel.

New Chandra data of this system, known as X9, show 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. Chandra data also shows evidence for large amounts of oxygen in the system, a characteristic feature of white dwarfs. A strong case can, therefore, be made that the companion star is a white dwarf, which would then be orbiting the black hole at only about 2.5 times the separation between the Earth and the Moon.

These latest findings build on work carried out by Christian Knigge, Professor of Astrophysics, at the University of Southampton, which found that the X9 system was an accreting compact object in a close binary system.

Professor Knigge, who is one of the authors on the paper, said: “Based on what we saw and the fact that white dwarfs are far more common than neutron stars or black holes, we suggested (in line with previous work) that the source was probably an accreting white dwarf.

“This is an extremely exciting result, because this may be the first black hole discovered to date that is fed by a white dwarf companion in this kind of ultra-compact configuration.â€?

“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,â€? said first author Arash Bahramian of the University of Alberta in Edmonton, Canada, and Michigan State University in East Lansing. “Luckily for this star, we don’t think it will follow this path into oblivion, but instead will stay in orbit.â€?



Although the white dwarf does not appear to be in danger of falling in or being torn apart by the black hole, its fate is uncertain. 



“Eventually so much matter may be pulled away from the white dwarf that it ends up only having the mass of a planet,â€? said co-author Craig Heinke, also of the University of Alberta. “If it keeps losing mass, the white dwarf may completely evaporate.â€?



How did the black hole get such a close companion? One possibility is that the black hole smashed into a red giant star, and then gas from the outer regions of the star was ejected from the binary. The remaining core of the red giant would form into a white dwarf, which becomes a binary companion to the black hole. The orbit of the binary would then have shrunk as gravitational waves were emitted, until the black hole started pulling material from the white dwarf.

The gravitational waves currently being produced by the binary have a frequency that is too low to be detected with Laser Interferometer Gravitational-Wave Observatory, LIGO, that has recently detected gravitational waves from merging black holes. Sources like X9 could potentially be detected with future gravitational wave observatories in space.

An alternative explanation for the observations is that the white dwarf is partnered with a neutron star, rather than a black hole. In this scenario, the neutron star spins faster as it pulls material from a companion star via a disk, a process that can lead to the neutron star spinning around its axis thousands of times every second. A few such objects, called transitional millisecond pulsars, have been observed near the end of this spinning up phase. The authors do not favor this possibility as transitional millisecond pulsars have properties not seen in X9, such as extreme variability at X-ray and radio wavelengths. However, they cannot disprove this explanation.


“We’re going to watch this binary closely in the future, since we know little about how such an extreme system should behaveâ€?, said co-author Vlad Tudor of Curtin University and the International Centre for Radio Astronomy Research in Perth, Australia. “We’re also going to keep studying globular clusters in our galaxy to see if more evidence for very tight black hole binaries can be found.â€?



A paper describing these results was recently accepted for publication in the Monthly Notices of the Royal Astronomical Society and is available online.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Enquiring minds can lose themselves in over 120 hands-on activities, talks, shows and tours across Highfield and Boldrewood campuses this Saturday at the University of Southampton’s 15th Science and Engineering Day.

The award-winning event sees the University open its doors for all to explore the world of science, technology, engineering and maths (STEM). The pinnacle of the week-long Southampton Science and Engineering Festival (SOTSEF), Saturday’s programme is free to attend and suitable for all.

Attractions at the event have been divided into 11 coloured zones which visitors can preview in advance through the SOTSEF website. The Physics and Astronomy building at the south of Highfield Campus will be advertised with yellow coloured signs on the day, leading visitors to PlayDoh planets, a Planeterella and three STEM shows: science spectacular Accelerate!, live planetarium The Astrodome and laser light display The Light Express Roadshow.

Researchers from Electronics and Computer Science will be exhibiting across the three zones on Highfield Campus. Highlights include a workshop for Mini Professors, an adventure with Aladdin and the Mystery of the Flying Carpet and the Future Worlds startup incubator’s SharkStream motion capture suit when following black arrows, tours of the Tony Davies High Voltage Laboratory from orange and a ‘Science Magic… Magic Science’ show in white.

Designed to inspire scientists of all ages, the event also includes an outdoor Archaeology Village and a Biodiversity Hub in the Valley Gardens. A free shuttle bus will take visitors to the Boldrewood Campus throughout the day, transporting people along a green route to over 20 attractions. Campus hosts will invite guests to learn about The Science of Ships in a special tour of the University’s 138m Towing Tank.

For more information, visit the SOTSEF website.

Dr Matthew Aldous, from Physics & Astronomy at the University of Southampton, took Silver at a competition in the House of Commons, for the excellence of his physics research, walking away with a £2,000 prize.

Matthew, a Postdoctoral Research Assistant in the Quantum Light and Matter research group, presented his physics research to dozens of politicians and a panel of expert judges, as part of the poster competition STEM for Britain, on Monday 13 March.

His research, which focuses on the development of a laser cooling system for the super cooling of gas atoms for use in quantum devices, was judged against 29 other shortlisted researchers’ work and came out as one of the three winners.

Matthew said, “It’s just fantastic to have the opportunity to talk to parliamentarians about the work that I do. It’s really great to be around so many brilliant scientists who have worked really hard to be here today and to share my research with them and to see the research that they have brought to share with the rest of the world.â€?

The Faculty of Physical Sciences and Engineering – home to Physics & Astronomy, Electronics and Computer Science (ECS) and the Optoelectronics Research Centre (ORC) – also saw the Gold prize in the Engineering category going to Miguel Xavier, a PhD student from ECS. Ten other researchers from across the University were also shortlisted to present their research, including Christopher Desira from Physics & Astronomy, Xiaoqing Shi from ECS and Dr Edward Rogers from the ORC.

Dean of the Faculty, Professor Bashir Al-Hashimi said “This double success at the STEM for Britain competition 2017 is testament to the excellent research activities in this Faculty and their impact, recognised through high-profile national events. STEM for Britain is prestigious and therefore extremely competitive, with candidates from highly-rated universities across the UK taking part. To win both a gold and silver medal on the same day is a fantastic achievement.â€?

STEM for Britain aims to help politicians understand more about the UK’s thriving science and engineering base and rewards some of the strongest scientific and engineering research being undertaken in the UK.

Stephen Metcalfe MP, Chair of the Parliamentary & Scientific Committee, sponsors of the physics awards said: “The Parliamentary & Scientific Committee is delighted to sponsor the physics awards. This annual competition is an important date in the parliamentary calendar because it gives MPs an opportunity to speak to a wide range of the country’s best young researchers. These early career engineers, mathematicians and scientists are the architects of our future and STEM for Britain is politicians’ best opportunity to meet them and understand their work.â€?

Professor Roy Sambles, President of the Institute of Physics said: “STEM for Britain provides a great opportunity for some of our outstanding young scientists to present aspects of their research in parliament, allowing Members of Parliament to find out first-hand about some of the ground breaking research taking place here in the UK. I wish the best of luck to all the exhibitors, who should feel very pleased with what they have achieved and I hope that they will value sharing the excitement of their research with key politicians and policy makers.â€?

Image caption: L to R: Dr Stephen Benn, Vice President, Parliamentary & Scientific Committee; Professor Paul Hardaker, Chief Executive, Institute of Physics; Dr Matthew Aldous (Silver Award Winner); Stephen Metcalfe MP, Chair, Parliamentary & Scientific Committee (Silver Sponsor).

Researchers from Physics and Astronomy, and the Faculty of Physical Sciences and Engineering at the University of Southampton, will be attending Parliament today to present their research to a range of politicians and a panel of expert judges, as part of STEM for Britain.

Christopher Desira, undergraduate student in the Physics and Astronomy department, and Dr Matthew Aldous, from the Quantum Light and Matter Group, were shortlisted from hundreds of applicants to appear in Parliament. Their research will be presented as posters, and judged against those of other scientists and engineers in the only national competition of its kind.

Christopher Desira is presenting his research on the classification of small (sub-kilometer) near-Earth asteroids. These are the most common kind of asteroids, and the first that will be reached by humans and exploited for their rich resources. Christopher says, “I’m very honoured to have been selected to attend the event. This competition provides me with an opportunity to convey the importance of near-Earth asteroid research in the UK, with asteroid mining likely to become a real and profitable industry within the next decade.â€?

Dr Matthew Aldous will be covering his work into developing a compact, portable system for generating ultracold atoms – a universal platform for quantum sensing which will unlock its unparalleled potential to the world. Matthew says, “I am delighted to receive the opportunity to present my work to some of the UK's parliamentary decision makers in this competition. The importance of continued investment in Quantum Technologies to the UK's economy, security and society cannot be overstated, and it will be marvellous to demonstrate first-hand what the government's support means to people working in this field."

Christopher and Matthew are joined in the competition alongside three other researchers from the Faculty of Physical Sciences and Engineering. Xiaoqing Shi and Miguel Xavier are PhD students in Electronics and Computer Science, and Dr Edward Rogers is from the Faculty’s Optoelectronics Research Centre.

• Xiaoqing is presenting her research into developing a new patterning technique that uses a focused beam of helium ions on novel materials. This could enable the rapid prototyping of novel future nanoelectronic devices and ultimately offers exciting possibilities to continue the miniaturization of electronics into the sub-10 nm regime. • Miguel’s research poster shows the development of new techniques based on microfluidics to isolate skeletal stem cells from human bone marrow and promote bone regeneration. • Edward has built a new type of microscope that does not need to label the samples with the toxic dyes that are used by competing systems, allowing us to look at living systems in their natural state in unprecedented detail.

Stephen Metcalfe MP, Chairman of the Parliamentary and Scientific Committee, says: “This annual competition is an important date in the parliamentary calendar because it gives MPs an opportunity to speak to a wide range of the country’s best young researchers.â€?

Taking place during British Science Week, STEM for Britain aims to encourage, support and promote Britain's early-stage and early-career research scientists, engineers, technologists and mathematicians. Awards are made on the basis of the very best research work and results together with researchers’ ability to communicate their work to a lay audience.

Christopher, Matthew and Edward’s work has been entered into the Physics session of the competition; Xiaoqing and Miguel’s has been entered into the Engineering session. Each session will end in a gold, silver and bronze prize-giving ceremony, judged by leading academics. The gold medalist from each session receives £3,000, while silver and bronze receive £2,000 and £1,000 respectively.

The Parliamentary and Scientific Committee runs the event in collaboration with the Royal Academy of Engineering, the Royal Society of Chemistry, the Institute of Physics, the Royal Society of Biology, The Physiological Society and the Council for Mathematical Sciences, with financial support from the Warwick Manufacturing Group, Clay Mathematics Institute, Heilbronn Institute for Mathematical Research, Institute of Biomedical Science and the Society of Chemical Industry.