In a controversial new paper in the journal Nature, astronomers from Queen's University Belfast have proposed a new physical interpretation of a supernova discovered on 7th November 2008.
A group of researchers, led by Dr. Stefano Valenti from Queen's University Belfast, found a weak explosion that is unusual in many ways, and several lines of evidence suggest it could be from a massive star.
This goes against mainstream thinking in the astrophysics community which believes that this type of supernova comes from old white dwarf stars (low-mass stars) in binary systems.
The supernova in question SN2008ha was a faint explosion that contained no hydrogen.
In their paper however, Valenti and his colleagues propose that the peculiar spectrum and faint luminosity of the supernovae in question, SN2008ha, more closely resembles those supernovae associated with the death of massive stars when their core collapses.
The key difference with the other faint explosion of massive stars was the lack of hydrogen which is usually detected in underluminous Supernovae.
Dr Valenti said "SN2008ha is the most extreme example of a group of supernovae that show similar properties. Up until now the community had thought that they were from the explosion of white dwarfs, which we call type Ia supernovae. Those are the ones that have been used to measure the geometry of the distant Universe and infer the existence of dark energy. But we think SN2008ha doesn't quite fit this picture and appears physically related to massive stars"
Professor Stephen Smartt from Queen's added "This is still quite controversial, we have put this idea forward and it certainly needs to be taken seriously.
"The implications are quite important. If this is a massive star explosion then it is the first one that might fit the theoretical models of massive stars that lose their outer layers through their huge luminosity pressure and then, perhaps, collapse to black holes with a whimper".
Dr Valenti's team is keen to use new deep, time resolved surveys of the Universe to find more of these and test their ideas. One such experiment is the first of the Pan-STARRS telescopes that has started surveying the sky in the last month.
The supernova in question was found in the galaxy UGC12682 in the constellation Pegasus by American school girl Caroline Moore, a member of the Puckett Observatory Supernova Search team.
It was immediately recognized by professional astronomers as quite unique, as it was one of the faintest explosions of its type ever discovered, with an energy approximately 50 times smaller than usual. This is the equivalent of converting several earth masses completely into energy.
More information on the work of the scientists at Queen's Astrophysics Research Centre can be found at http://star.
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Notes to Editors
Professor Smartt and Dr Valenti are available for interview.
The paper can be found at
Supernovae are among the most energetic and powerful events in the universe as they are the explosions that end the life cycles of those stars eight times more massive than the Sun.
There is great diversity in the range of energies of the most common supernovae of this size, known as Type II. These are explosions of normal, hydrogen rich stars of such masses. Current thinking states this diversity is due to the different masses of the stars that explode and what is left behind in their cores.
When the cores of the most massive stars collapse many astrophysicists currently believe they leave behind neutron stars, but if the core is massive enough then theoretical models predict that a black hole may form. This means so much matter is swallowed there is not enough high energy material and radioactive material to produce a bright explosion.
Queen's Astrophysics Research Centre (ARC) carries out research in a number of stellar, Galactic and solar system areas. It is an observational astronomy group employing both large ground-based telescopes and space observatories including the European Southern Observatory, Gemini and the Hubble Space Telescope. There is also a programme on the study of laboratory plasmas and their astrophysical counterparts. Research is currently supported by several substantial PPARC and EPSRC grants.
Research topics include:
- Hot stars
- Cool stars and the Sun
- Comets and asteroids
- WASP - Wide Angle Search for Planets
- Interstellar medium
- Astronomical and laboratory plasmas
- nonLTE modelling of stellar atmospheres
- Molecular astrophysics