These events occur more frequently than expected

Jan 8, 2010 15:42 GMT  ·  By
Snapshots of the simulated merger of two white dwarfs to create a Type Ia supernova
   Snapshots of the simulated merger of two white dwarfs to create a Type Ia supernova

Astronomers have recently determined that some of the supernova explosions we see in the night skies are in fact triggered by stars known as white dwarfs merging in a violent, cataclysmic event. The findings can help explain why some of the massive blasts that follow, which are so precise that they are currently used to gauge distances between various celestial objects in the Universe, are so different in luminosity than others. While most feature a specific peak luminosity, others are much dimmer, and astronomers failed to find an explanation for this until now, Space Fellowship reports.

Type Ia supernovae are cosmic explosions that release enormous amounts of energy and light. They can be seen from afar, and have become “standard candles” over the years, reference points in measuring distances in the Cosmos. At the 215th meeting of the American Astronomical Society (AAS), held in Washington DC, experts who have taken an interest in white dwarfs say that these stars merge a lot more often than initially thought, and also that these collisions can help explain some of the peculiarities of Type Ia supernovae.

German astronomers from the Max-Planck Institute for Astrophysics, in Garching, showed at the meeting details of a simulation they conducted, of a binary system featuring two white dwarfs becoming unstable. In their scenario, the two stars slammed into each other and exploded, but the resulting supernova was a lot less luminous than one would expect from a Type Ia. The work clears the mystery associated with a famous supernova explosion, dubbed 1991bg, which was dimmer than anyone expected, and for which no clear explanation has been provided until now.

In the simulation, both white dwarfs had masses just below that of our Sun. The work shows that a lot of energy is lost from the system as the two components approach each other, mostly under the form of gravitational waves. “With our detailed explosion simulations, we could predict observables that indeed closely match actual observations of Type Ia supernovae,” Max Planck expert Friedrich Ropke, who is also a coauthor of the paper, explains. Additional details of the study also appear in the January 7 issue of the esteemed scientific journal Nature.