|
|
First supernova companion star found 
A joint European/University of Hawaii team of astronomers has for the first time observed a stellar ‘survivor’ to emerge from a double star system involving an exploded supernova. Supernovae are some of the most significant sources of chemical elements in the Universe, and they are at the heart of our understanding of the evolution of galaxies. Supernovae are some of the most violent events in the Universe. For many years astronomers have thought that they occur in either solitary massive stars (Type II supernovae) or in a binary system where the companion star plays an important role (Type I supernovae). However no one has been able to observe any such companion star. It has even been speculated that the companion stars might not survive the actual explosion...
Initially rather ordinary, SN 1993J began to puzzle astronomers as its ejecta seemed too rich in the chemical element helium and instead of fading normally it showed a bizarre sharp increase in brightness. The astronomers realised that a normal red supergiant alone could not have given rise to such a weird supernova. It was suggested that the red supergiant orbited a companion star that had shredded its outer layers just before the explosion.
This is the first supernova companion star ever to be detected and it represents a triumph for the theoretical models. In addition, this observation allows a detailed investigation of the stellar physics leading to supernova explosions. It is now clear that during the last 250 years before the explosion 10 solar masses of gas were torn violently from the red supergiant by its partner. By observing the companion closely in the coming years it may even be possible to detect a neutron star or black hole emerge from the remnants of the explosion ‘in real time’.
Given the paucity of observations of supernova progenitor systems this result, published in Nature on 8 January 2004, is likely to 'be crucial to understanding how very massive stars explode and why we see such peculiar supernovae' according to first author Justyn R. Maund from the University of Cambridge, UK.
Stephen Smartt, also from the University of Cambridge, says, “Supernova explosions are at the heart of our understanding of the evolution of galaxies and the formation of chemical elements in the Universe. It is essential that we know what type of stars produce them.”
For the last ten years astronomers have believed that they could understand the very peculiar behaviour of 1993J by invoking the existence of a binary companion star and now this picture has proved correct.
According to Rolf Kudritzki, from the University of Hawaii, “The combination of the outstanding spatial resolution of Hubble and the huge light gathering power of the Keck 10- metre telescope in Hawaii has made this fantastic discovery possible.”
This huge energy release causes the visible supernova we see. While astronomers are convinced that observations will match this theoretical model, they are in the embarrassing position that they have confidently identified only two stars that later exploded as supernovae – the precursors of supernovae 1987A and 1993J.
Supernovae appear in spiral galaxies like M81 on average once every 100 years or so. The team, led by Stephen Smartt, hope to increase the numbers of supernova progenitors known from 2 to 20 over the next five years. Notes for editors The team is composed of Stephen J. Smartt and Justyn R. Maund (University of Cambridge, UK), Rolf. P. Kudritzki (University of Hawaii, USA), Philipp Podsiadlowski (University of Oxford, UK) and Gerry F. Gilmore (University of Cambridge, UK).
Animations of the discovery and general Hubble Space Telescope
background footage are available from
http://www.spacetelescope.org/video/heic0401_vnr.html
For more information, please contact: Justyn R. Maund University of Cambridge Tel: +44 (0)1223 337544 E-mail: jrm@ast.cam.ac.uk
Stephen Smartt
Rolf. P. Kudritzki
Lars Lindberg Christensen
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
