A new class of dim supernovae

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Colour image of supernova SN 2008ha taken on 2008 December 30 at Calar Alto Observatory, with the Zeiss 2.2m Telescope and camera CAFOS. It is a composite of the B, V and R bands. The SN is the faint reddish dot marked with an arrow. The quite irregular shape of the galaxy UGC 12682, that hosts the supernova, is seen at the centre of the image. Stefan Taubenberger, Max Planck Institut for Astrophysics.

The colossal stellar explosions called supernovae come in many kinds and flavours. Some of them are produced when a massive star reaches the end of its life in a sudden gravitational collapse. Astronomers have just found one of these explosions that defies the current classification scheme. The results of this research have been published in Nature, and Calar Alto has contributed to this discovery.

Core-collapse (or gravitational) supernovae are among the most energetic and violent events in the universe. They constitute the final tremendous explosions that end the life cycles of stars more massive than approximately 8 times the Sun. After running out of fuel, the core of such a star collapses and forms a neutron star or a black hole. At the same time, the outer layers are ejected at high velocity (up to 10% of the speed of light) and shine as brightly as billions of stars together. The total energy suddenly released by such a typical supernova exceeds the total energy release of the Sun during its whole past and future life time of 10 billion years.

However, some core-collapse supernovae are up to 100 times less energetic and luminous than usual. These low-power explosions normally show the presence of hydrogen gas, but a new event, supernova SN 2008ha, is the first dim supernova in which no hydrogen could be detected. This research has been performed by an international team lead by the Italian astronomer Stefano Valenti (Queen's University in Belfast, United Kingdom), including scientists from Max Planck Institute for Astrophysics (Germany), the National Institute for Astrophysics (Italy), and various other institutions. The results, recently published in the scientific journal Nature, are based on data gathered at Calar Alto Observatory (Andalusia, Spain), the Telescopio Nazionale Galileo (TNG), Nordic Optical Telescope (NOT) and Liverpool Telescope (all in Canary Islands, Spain), the Copernico Telescope (Asiago Observatory, Italy), and other smaller observational facilities.

Taken together, the dimness and lack of hydrogen leave room for two scenarios for the origin of SN 2008ha. One possibility is that the progenitor star may have been a moderately massive star in a binary system, which lost its outer layers through the interaction with the companion. Alternatively, the explosion may be due to a very massive star which shed its envelope through stellar winds and formed a black hole upon core collapse. If the latter scenario should prove to be correct, SN 2008ha may be of particular importance in our understanding of the connection between supernovae and a group of gamma-ray bursts.

The tale of SN 2008ha is one more step in an ongoing research program whose goal is to unveil the secrets of these cosmic explosions. This project involves an international team of scientists from many institutions and relies on observational data from different observatories and instruments. No doubt this exploration will produce more exciting news in the near future.

Colour image of supernova SN 2008ha taken on 2008 December 30 at Calar Alto Observatory, with the Zeiss 2.2m Telescope and camera CAFOS. It is a composite of the B, V and R bands. The SN is the faint reddish dot marked with an arrow. The quite irregular shape of the galaxy UGC 12682, that hosts the supernova, is seen at the centre of the image. Stefan Taubenberger, Max Planck Institut for Astrophysics.

More information: S. Valenti et al., Nature 459, 674-677 (4 June 2009)

Provided by Calar Alto Observatory

   

• LuckyBrandon - Jun 06, 2009
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  that's just the aliens turning their lights on and off when they get home from work :)
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• yyz - Jun 07, 2009
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  I was at first curious as to how the researchers accounted for internal galactic absorption in this particular supernova. Upon reading a copy of the preprint: http://arxiv.org/...2074.pdf I see they found very little intrinsic absorption in this galaxy. The paper also brings up implications for nearby long GRBs and has several other peculiar SNe highlighted. Unusually dim luminosity coupled with missing hydrogen lines rightly needs to be adequately explained.
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• omatumr - Jun 07, 2009
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  WHY COSMIC OBSERVATIONS DEFY COSMIC MODELS
  
  Stellar explosions are powered by the same energy source that powers the Sun, ordinary stars and releases H as an exhaust gas into interstellar space:
  
  Repulsive interactions between neutrons. See: http://www.lpi.us...1041.pdf
  
  With kind regards,
  Oliver K. Manuel
  http://myprofile....anuelo09
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• LuckyBrandon - Jun 07, 2009
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  if that were true oliver, wouldnt there be many more supernovae, and in fact, wouldnt earth have likely subjected to them already?
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• yyz - Jun 17, 2009
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  @omatumr, if "stellar explosions" ..."releases H as an exhaust gas into interstellar space", then why was this supernova deficient in hydrogen, as stated in the article? How does your theory account for this observation along with the observed low luminosity of the event itself?
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