Scientists have been tracking the occurrence of star explosions, or supernovae, since they were first observed. Recently, a team of astronomers, including Associate Wendy Freedman (Carnegie Institution of Science), revealed the existence of a new, smaller kind of supernova that had previously been unrecognized. The team’s findings have been published in The Astrophysical Journal.
An artist’s conception of the supernova called Type Iax.
Credit: Christine Pulliam (CfA).
Until now, only two kinds of supernovae had been classified: core-collapse and Type la. Core-collapse supernovas are giant star explosions that are 10 to 100 times more massive than the Sun of our solar system. Type Ia supernovaes typically occur as a two-star (binary) system, with one star collapsed, referred to as a white dwarf. Type Ia emits light that is easily predicted by scientists and has been used to measure the expansion of the Universe.
The newest kind of supernova is called Type Iax. It is fainter and less energetic than the other two known to date. “A Type Iax is like a mini supernova,” says Freedman. “Unlike a Type Ia, it appears that there is a failed explosion that does not entirely disrupt the white dwarf companion star.”
The research team found 25 examples of this new supernova in what they believe are younger star systems; yet, still don`t know what causes this new type of supernova to occur. Like the Type Ia, the Type Iax comes from a binary star system containing a white dwarf and a companion. What is unique about the mini supernovae is that the white dwarf star remains intact, unlike Type Ia in which it is completely destroyed.
The team calculated that Type Iax are about a third as common as Type Ia supernovae. The reason that so few have been detected is because they are one hundred times fainter.
“In the next decade, new and deeper surveys of the sky are likely to reveal other classes of here-to-fore undiscovered rare and/or faint objects,” says Freedman. “In many ways, we are still scratching the surface of the known universe.”
This research was supported by a Clay Fellowship, the National Science Foundation, Gary & Cynthia Bengier, the Richard & Rhoda Goldman Fund, the Christopher R. Redlich Fund, the TABASGO Foundation, Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, the University of California, the Sylvia & Jim Katzman Foundation, the Danish Agency for Science and Technology and Innovation, the Millennium Center for Supernova Science with input from “Fondo de Innovacion para la Competitividad, del Ministerio de Economıa, Fomento y Turismo de Chile,” and CONICYT.