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The Glowing Halo of a Zombie Star

Last Updated on Thursday, 12 November 2015 16:52
Published on Wednesday, 11 November 2015 11:00

Astronomers have studied the remains of a fatal interaction between a dead star and its asteroid supper in detail for the first time, giving us a glimpse of the distant fate of the Solar System. The international team, who used the Very Large Telescope (VLT) at the European Southern Observatory’s Paranal site in Chile, publishes its work in Monthly Notices of the Royal Astronomical Society.

eso1544c smallThis plot is an unusual type of image, showing the velocities of the gas in the disc around the white dwarf SDSS J1228+1040, rather than its position. It was mapped out from Very Large Telescope observations over a period of twelve years and by applying a method called Doppler tomography. The dashed circles correspond to material in circular orbits at two different distances from the star. This appears “inside out” because material moves faster in close-in orbits. Credit: University of Warwick/C. Manser/ESO. Click for a larger imageLed by Christopher Manser, a PhD student at the University of Warwick in the United Kingdom, the team used data from the VLT and other observatories to study the shattered remains of an asteroid around a stellar remnant – a white dwarf called SDSS J1228+1040.

Using several instruments, including the Ultraviolet and Visual Echelle Spectrograph (UVES) and X-shooter, both attached to the VLT, the team obtained detailed observations of the light coming from the white dwarf and its surrounding material over an unprecedented period of twelve years between 2003 and 2015. Observations over periods of years were needed to probe the system from multiple viewpoints.

“The image we get from the processed data shows us that these systems are truly disc-like, and reveals many structures that we cannot detect in a single snapshot,” explained Manser.

The team used a technique called Doppler tomography — similar in principle to medical scans of the human body — which allowed them to make the first detailed map of the structure of the glowing gaseous remains of the dead star’s meal orbiting J1228+1040.

While large stars — those more massive than around ten times the mass of the Sun — suffer a spectacularly violent climax as a supernova explosion at the ends of their lives, smaller stars are spared such dramatic fates. When stars like the Sun come to the ends of their lives they exhaust their fuel, expand as red giants and later expel their outer layers into space. The hot and very dense core of the former star — a white dwarf — is all that remains.

But would the planets, asteroids and other bodies in such a system survive this trial by fire? What would be left? The new observations help to answer these questions.

eso1544a smallThis artist’s impression shows how an asteroid torn apart by the strong gravity of a white dwarf has formed a ring of dust particles and debris orbiting the Earth-sized burnt out stellar core SDSS J1228+1040. Gas produced by collisions within the disc is detected in observations obtained over twelve years with ESO’s Very Large Telescope, and reveal a narrow glowing arc. Credit: Mark Garlick (http://www.markgarlick.com) and University of Warwick/ESO. Click for a larger imageIt is rare for white dwarfs to be surrounded by orbiting discs of gaseous material — only seven have ever been found. The team concluded that an asteroid had strayed dangerously close to the dead star and been ripped apart by the immense tidal forces it experienced to form the disc of material that is now visible.

The orbiting disc was formed in similar ways to the photogenic rings seen around planets closer to home, like Saturn. However, while J1228+1040 is more than seven times smaller in diameter than the ringed planet, it has 2500 times its mass. The team learned that the distance between the white dwarf and its disc is also quite different — Saturn and its rings could comfortably sit in the gap between them.

The new long-term study with the VLT has also now enabled the team to watch the disc precess under the influence of the very strong gravitational field of the white dwarf. They find too that the disc is somewhat lopsided and has not yet become circular.

“When we discovered this debris disc orbiting the white dwarf back in 2006, we could not have imagined the exquisite details that are now visible in this image, constructed from twelve years of data — it was definitely worth the wait,” added Boris Gänsicke, a co-author of the study.

Remnants such as J1228+1040 can provide key clues to understanding the environments that exist as stars reach the ends of their lives. This can help astronomers to understand the processes that occur in planetary systems, and even forecast the fate of the Solar System when the Sun meets its demise in about seven billion years’ time.

 


Science contacts

 

Christopher Manser
University of Warwick
United Kingdom
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Boris Gänsicke
University of Warwick
United Kingdom
Tel:  +44 (0)2476574741
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Media contacts

 

Tom Frew
International Press Officer, University of Warwick
United Kingdom
Tel: +44 (0)24 7657 5910
Mob: +44 (0)7785 433 155
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Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Mob: +49 151 1537 3591
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More information

 

This research appears in “Doppler-imaging of the planetary debris disc at the white dwarf SDSS J122859.93+104032.9”, C. Manser et al., Monthly Notices of the Royal Astronomical Society, Oxford University Press, in press. Download a preprint of the paper here.

The team is composed of Christopher Manser (University of Warwick, UK), Boris Gaensicke (University of Warwick), Tom Marsh (University of Warwick), Dimitri Veras (University of Warwick, UK), Detlev Koester (University of Kiel, Germany), Elmé Breedt (University of Warwick), Anna Pala (University of Warwick), Steven Parsons (Universidad de Valparaiso, Chile) and John Southworth (Keele University, UK).

 

See the full ESO press release for full size images and videos.

 


Notes for editors

 

The European Southern Observatory, 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”.

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3900 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

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