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AsianScientist (Jun. 15, 2016) – Astronomers who are part of the Optical and Infrared Synergetic Telescopes for Education and Research (OISTER) telescope consortium in Japan have uncovered new information about the origin of ‘extraordinary supernovae’ explosions, which are brighter than normal ones.

Type Ia supernovae are a type of exploding star. What makes these supernovae useful is that the brightness of a Type Ia supernova explosion is consistent from one star to the next. By using the ‘known brightness’ of these supernovae, astronomers can use them to calibrate observations when studying the Universe.

But it turns out there’s a problem with this method. In addition to normal Type Ia supernovae, astronomers have discovered extraordinary supernovae, which are much brighter than they should be. These extraordinary supernovae may be contaminating the samples used for cosmological research, thereby skewing calibrations. Thus, it is crucial to determine the origins of both typical and extraordinary supernovae so that the latter can be more accurately excluded from the sample.

There are two popular scenarios as the path to the supernova explosion: accretion or merger. Both scenarios consider a binary system of two stars orbiting around each other. The accretion scenario uses binary systems composed of one white dwarf and one normal star, and the merger scenario uses binary systems formed by two white dwarfs.

When the extraordinary supernovae candidate SN 2012dn was spotted, researcher Dr. Masayuki Yamanaka from Konan University and colleagues observed it for 150 days using 11 OISTER telescopes in Japan. They discovered an unusual strong infrared emission for this object which is not seen in typical supernovae.

The groups performed detailed analysis of the infrared emission, and concluded that it supports the accretion scenario. In this scenario, gas is transferred onto the surface of the white dwarf from the companion star in the binary system, where it then begins to emit infrared radiation.

During the gas transfer, a part of the material escapes from the gravitational field of the system and forms a dense gas cloud around the star system. The observation results indicate that SN 2012dn exploded while surrounded by this dense gas cloud.

Their findings, published in Publications of the Astronomical Society of Japan, will help improve measurements of both the Universe’s expansion and the dark energy that controls the final fate of the cosmos.


The article can be found at: Yamanaka et al. (2016) OISTER Optical and Near-Infrared Observations of the Super-Chandrasekhar Supernova Candidate SN 2012dn: Dust Emission from the Circumstellar Shell.

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Source: National Institutes of Natural Sciences; Photo: Higashi-Hiroshima Observatory.
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