Scientists using the world’s biggest digital camera, the Large Synoptic Survey Telescope (LSST) in northern Chile, have observed for the first time a third type of supernova, marking a significant step forward in our understanding of how matter is introduced into the universe.
Previously observed supernovae had been placed in two categories: the core collapse supernova, where stars 10 to 100 times larger than the sun explode violently, and the Type Ia supernova, described as the complete disruption of a white dwarf.
In the newly discovered kind of supernova, called Type Iax, white dwarfs are only partially disrupted, and part of the star may remain intact after the event.
“A Type Iax supernova is essentially a mini supernova,” Ryan Foley, Clay Fellow at the Harvard-Smithsonian Center for Astrophysics (CfA) and lead author on the study, said. “It’s the runt of the supernova litter.”
Foley and his colleagues have observed 25 Type Iax supernova, and none have been found in elliptical galaxies of old stars, suggesting the events only occur in young star systems.
Researchers have concluded that Iax supernovae occur in binary star systems, where a host star loses its outer shell of hydrogen, exposing an inner shell of helium that is then violently leached away by a nearby white dwarf. The white dwarf is massively disrupted by this process, but remains partially intact.
Scientists are unsure of the cause of the Iax supernova. One theory is that the outer helium layer of the host star ignites first, sending a shock wave into the white dwarf. Another possibility is that the white dwarf might ignite first due to the influence of the overlying helium shell.
Whatever the case, the most striking phenomenon is that, unlike in the Ia supernova, much of the white dwarf survives the explosion.
“The star will be battered and bruised, but it might live to see another day,” Foley said.
The Iax supernova had until now eluded astronomers as it is a very low energy supernova. However, the advanced technology of the LSST, that includes a 3200 megapixel camera, makes the telescope perfectly suited to imaging faint astronomical objects across the sky.
“Type Iax supernovas aren’t rare, they’re just faint,” Foley said. “For more than a thousand years, humans have been observing supernovas. This whole time, this new class has been hiding in the shadows.”
Due to its almost non-existent humidity and clear skies, northern Chile is the world’s premier location for astronomy. Chile is home to almost half the world’s telescope infrastructure, and this is set to increase to over two thirds in the next decade.