Nav: Home

White dwarf lashes red dwarf with mystery ray

July 27, 2016

In May 2015, a group of amateur astronomers from Germany, Belgium and the UK came across a star system that was exhibiting behaviour unlike anything they had ever encountered. Follow-up observations led by the University of Warwick and using a multitude of telescopes on the ground and in space [1], have now revealed the true nature of this previously misidentified system.

The star system AR Scorpii, or AR Sco for short, lies in the constellation of Scorpius, 380 light-years from Earth. It comprises a rapidly spinning white dwarf [2], the size of Earth but containing 200 000 times more mass, and a cool red dwarf companion one third the mass of the Sun [3], orbiting one another every 3.6 hours in a cosmic dance as regular as clockwork.

In a unique twist, this binary star system is exhibiting some brutal behaviour. Highly magnetic and spinning rapidly, AR Sco's white dwarf accelerates electrons up to almost the speed of light. As these high energy particles whip through space, they release radiation in a lighthouse-like beam which lashes across the face of the cool red dwarf star, causing the entire system to brighten and fade dramatically every 1.97 minutes. These powerful pulses include radiation at radio frequencies, which has never been detected before from a white dwarf system.

Lead researcher Tom Marsh of the University of Warwick's Astrophysics Group commented: "AR Scorpii was discovered over 40 years ago, but its true nature was not suspected until we started observing it in 2015. We realised we were seeing something extraordinary within minutes of starting the observations."

The observed properties of AR Sco are unique. They are also mysterious. The radiation across a broad range of frequencies is indicative of emission from electrons accelerated in magnetic fields, which can be explained by AR Sco's spinning white dwarf. The source of the electrons themselves, however, is a major mystery -- it is not clear whether it is associated with the white dwarf itself, or its cooler companion.

AR Scorpii was first observed in the early 1970s and regular fluctuations in brightness every 3.6 hours led it to be incorrectly classified as a lone variable star [4]. The true source of AR Scorpii's varying luminosity was revealed thanks to the combined efforts of amateur and professional astronomers. Similar pulsing behaviour has been observed before, but from neutron stars -- some of the densest celestial objects known in the Universe -- rather than white dwarfs.

Boris Gänsicke, co-author of the new study, also at the University of Warwick, concludes: "We've known pulsing neutron stars for nearly fifty years, and some theories predicted white dwarfs could show similar behaviour. It's very exciting that we have discovered such a system, and it has been a fantastic example of amateur astronomers and academics working together."
-end-
Notes

[1] The observations underlying this research were carried out on: ESO's Very Large Telescope (VLT - http://www.eso.org/paranal/) located at Cerro Paranal, Chile; the William Herschel and Isaac Newton Telescopes of the Isaac Newton Group of telescopes sited on the Spanish island of La Palma in the Canaries; the Australia Telescope Compact Array at the Paul Wild Observatory, Narrabri, Australia; the NASA/ESA Hubble Space Telescope ; and NASA's Swift satellite .

[2] White dwarfs form late in the life cycles of stars with masses up to about eight times that of our Sun. After hydrogen fusion in a star's core is exhausted, the internal changes are reflected in a dramatic expansion into a red giant, followed by a contraction accompanied by the star's outer layers being blown off in great clouds of dust and gas. Left behind is a white dwarf, Earth-sized but 200 000 times more dense. A single spoonful of the matter making up a white dwarf would weigh about as much as an elephant here on Earth.

[3] This red dwarf is an M type star. M type stars are the most common class in the Harvard classification system, which uses single letters to group stars according their spectral characteristics. The famously awkward to remember sequence of classes runs: OBAFGKM, and is often remembered using the mnemonic Oh Be A Fine Girl/Guy, Kiss Me.

[4] A variable star is one whose brightness fluctuates as seen from Earth. The fluctuations may be due to the intrinsic properties of the star itself changing. For instance some stars noticeably expand and contract. It could also be due to another object regularly eclipsing the star. AR Scorpii was mistaken for a single variable star as the orbiting of two stars also results in regular fluctuations in observed brightness.

More information

This research was presented in a paper entitled "A radio pulsing white dwarf binary star", by T. Marsh et al., to appear in the journal Nature on 28 July 2016.

The team is composed of T.R. Marsh (University of Warwick, Coventry, UK), B.T. Gänsicke (University of Warwick, Coventry, UK), S. Hümmerich (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO), USA) , F.-J. Hambsch (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO), USA; Vereniging Voor Sterrenkunde (VVS), Belgium), K. Bernhard (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO),USA), C.Lloyd (University of Sussex, UK), E. Breedt (University of Warwick, Coventry, UK), E.R. Stanway (University of Warwick, Coventry, UK), D.T. Steeghs (University of Warwick, Coventry, UK), S.G. Parsons (Universidad de Valparaiso, Chile), O. Toloza (University of Warwick, Coventry, UK), M.R. Schreiber (Universidad de Valparaiso, Chile), P.G. Jonker (Netherlands Institute for Space Research, The Netherlands; Radboud University Nijmegen, The Netherlands), J. van Roestel (Radboud University Nijmegen, The Netherlands), T. Kupfer (California Institute of Technology, USA), A.F. Pala (University of Warwick, Coventry, UK) , V.S. Dhillon (University of Sheffield, UK; Instituto de Astrofisica de Canarias, Spain; Universidad de La Laguna, Spain), L.K. Hardy (University of Warwick, Coventry, UK; University of Sheffield, UK), S.P. Littlefair (University of Sheffield, UK), A. Aungwerojwit (Naresuan University, Thailand), S. Arjyotha (Chiang Rai Rajabhat University, Thailand), D. Koester (University of Kiel, Germany), J.J. Bochinski (The Open University, UK), C.A. Haswell (The Open University, UK), P. Frank (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany) and P.J. Wheatley (University of Warwick, Coventry, UK).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world's largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Links

* Research paper - http://www.eso.org/public/archives/releases/sciencepapers/eso1627/eso1627a.pdf

* Photos of the VLT - http://www.eso.org/public/images/archive/category/paranal/

Contacts

Tom Marsh
Department of Physics, University of Warwick
Coventry, United Kingdom
Tel: +44 24765 74739
Email: t.r.marsh@warwick.ac.uk

Boris Gänsicke
Department of Physics, University of Warwick
Coventry, United Kingdom
Tel: +44 24765 74741
Email: Boris.Gaensicke@warwick.ac.uk

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

ESO

Related Magnetic Fields Articles:

Visualizing strong magnetic fields with neutrons
Researchers at the Paul Scherrer Institute PSI have developed a new method with which strong magnetic fields can be precisely measured.
Scientists deepen understanding of magnetic fields surrounding Earth and other planets
Now, a team of scientists has completed research into waves that travel through the magnetosphere, deepening understanding of the region and its interaction with our own planet, and opening up new ways to study other planets across the galaxy.
Technique pulls interstellar magnetic fields within easy reach
A new, more accessible and much cheaper approach to surveying the topology and strength of interstellar magnetic fields -- which weave through space in our galaxy and beyond, representing one of the most potent forces in nature -- has been developed by researchers at the University of Wisconsin-Madison.
A bubbly new way to detect the magnetic fields of nanometer-scale particles
The method provides manufacturers with a practical way to measure and improve their control of the properties of magnetic nanoparticles for a host of medical and environmental applications.
Quantum sensing method measures minuscule magnetic fields
A new technique developed at MIT uses quantum sensors to enable precise measurements of magnetic fields in different directions.
The FASEB Journal: Magnetic fields enhance bone remodeling
Since the creation of 3D-printed (3DP) porous titanium scaffolds in 2016, the scientific community has been exploring ways to improve their ability to stimulate osteogenesis, or bone remodeling.
Tangled magnetic fields power cosmic particle accelerators
Magnetic field lines tangled like spaghetti in a bowl might be behind the most powerful particle accelerators in the universe.
Growing magnetic fields in deep space: Just wiggle the plasma
Astrophysicists have long wondered how cosmic magnetic fields fields are produced, sustained, and magnified.
Surprise finding: Discovering a previously unknown role for a source of magnetic fields
Feature describes unexpected discovery of a role the process that seeds magnetic fields plays in mediating a phenomenon that occurs throughout the universe and can disrupt cell phone service and knock out power grids on Earth.
Neutrons scan magnetic fields inside samples
With a newly developed neutron tomography technique, an HZB team has been able to map for the first time magnetic field lines inside materials at the BER II research reactor.
More Magnetic Fields News and Magnetic Fields Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Accessing Better Health
Essential health care is a right, not a privilege ... or is it? This hour, TED speakers explore how we can give everyone access to a healthier way of life, despite who you are or where you live. Guests include physician Raj Panjabi, former NYC health commissioner Mary Bassett, researcher Michael Hendryx, and neuroscientist Rachel Wurzman.
Now Playing: Science for the People

#544 Prosperity Without Growth
The societies we live in are organised around growth, objects, and driving forward a constantly expanding economy as benchmarks of success and prosperity. But this growing consumption at all costs is at odds with our understanding of what our planet can support. How do we lower the environmental impact of economic activity? How do we redefine success and prosperity separate from GDP, which politicians and governments have focused on for decades? We speak with ecological economist Tim Jackson, Professor of Sustainable Development at the University of Surrey, Director of the Centre for the Understanding of Sustainable Propserity, and author of...
Now Playing: Radiolab

An Announcement from Radiolab