An international team of astronomers has been able to see into the heart of an exploding star, by combining data from telescopes that are hundreds or even thousands of kilometres apart. Their results are published at 18:00 hours on Oct 8 2014 in the journal Nature.
Highly-detailed images produced using radio telescopes from across Europe and America have pinpointed the locations where a stellar explosion (called a nova), emitted gamma rays (extremely high energy radiation). The discovery revealed how the gamma-ray emissions are produced, something which mystified astronomers when they were first observed in 2012.
"We not only found where the gamma rays came from, but also got a look at a previously-unseen scenario that may be common in other nova explosions," said Laura Chomiuk, of Michigan State University.
Tim O'Brien of The University of Manchester's Jodrell Bank Observatory, one of the international team of astronomers who worked on the study, explains, "A nova occurs when gas from a companion star falls onto the surface of a white dwarf star in a binary system. This triggers a thermonuclear explosion on the surface of the star which blasts the gas into space at speeds of millions of miles per hour".
"When it explodes it brightens hugely, leading in some cases to the appearance of a new star in the sky, hence the term nova. These explosions are unpredictable, so when one goes off, the pressure is on for us to try and get as many of the world's telescopes as possible to take a look before it fades away. For this nova, our international team was primed and ready to go and we really came up trumps."
Astronomers did not expect this nova scenario to produce high-energy gamma rays. However, in June of 2012, NASA's Fermi spacecraft detected gamma rays coming from a nova called V959 Mon, some 6500 light-years from Earth.
At the same time, observations with the Karl G. Jansky Very Large Array (VLA) of telescopes in the USA indicated that radio waves coming from the nova were probably the result of subatomic particles moving at nearly the speed of light interacting with magnetic fields. The high-energy gamma-ray emission, the astronomers noted, also required such fast-moving particles.
Later observations from the telescopes of the European VLBI network (EVN) and the Very Long Baseline Array (VLBA) in the USA revealed two distinct knots of radio emission. These knots then were seen to move away from each other.
This observation, along with studies made with the e-MERLIN telescope array in the UK, and further VLA observations in 2014, provided the scientists with information that allowed them to put together a picture of how the radio knots, and the gamma rays, were produced.
In the first stage of this scenario, the white dwarf and its companion give up some of their orbital energy to boost some of the explosion material, making the ejected material move outward faster in the plane of their orbit. Later, the white dwarf blows off a faster wind of particles moving mostly outward along the poles of the orbital plane. When the faster-moving polar flow hits the slower-moving material, the shock accelerates particles to the speeds needed to produce the gamma rays, and the knots of radio emission.
"By watching this system over time and seeing how the pattern of radio emission changed, then tracing the movements of the knots, we saw the exact behaviour expected from this scenario," Chomiuk said.
A technique called radio interferometry, in which data from various radio telescopes are combined to obtain a sharper image, played a fundamental role in this result. By connecting together radio telescopes across tens, hundreds and even thousands of kilometres, the scientists were able to zoom in to get a much sharper view of the heart of this exploding star.
Gamma rays from several nova explosions have now been detected so it may be that the phenomenon is relatively common, but perhaps seen only when the nova is sufficiently close to Earth.
Because this type of ejection is also seen in other binary-star (two stars orbiting each other) systems, the new insights may help astronomers understand how those systems develop. The phase in which matter ejected from one star engulfs its companion occurs in all close binary stars, and is poorly understood.
"We may be able to use novae as a 'testbed' for improving our understanding of this critical stage of binary evolution," Chomiuk said.
Media enquiries to:
Media Relations Officer
The University of Manchester
Tel: 0161 275 8387
Notes to editors:
The paper: Binary orbits as the driver of gamma-ray emission and mass ejection in classical novae is by L. Chomiuk, J. D. Linford, J. Yang, T. J. O'Brien, Z. Paragi, A. J. Mioduszewski, R. J. Beswick, C. C. Cheung, K. Mukai, T. Nelson, V. A. R. M. Ribeiro, M. P. Rupen, J. L. Sokoloski, J. Weston, Y. Zheng, M. F. Bode, S. Eyres, N. Roy, G. B. Taylor, published in Nature and available online 18:00 hrs (London time) October 08 2014
Images: Artist's impressions of the gas ejected in the nova explosion with the binary star system at the centre are available on request. Picture:Credit: Bill Saxton, NRAO/AUI/NSF
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
e-MERLIN is operated by The University of Manchester for the UK's Science and Technology Facilities Council (STFC).
The European VLBI Network is a collaboration of the major radio astronomical institutes in Europe, Asia and South Africa and performs high angular resolution observations of cosmic radio sources.
The Joint Institute for VLBI in Europe (JIVE) is a scientific foundation based in the Netherlands with a mandate to support the operations of the European VLBI Network.
Katie Brewin | Eurek Alert!
Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory
SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences