Iron is a starkiller for stars at least 1.5 times larger than our sun. This is science fact, not science fiction.
"In the world of science fiction, there are many ideas about what a starkiller machine might be like. Strangely enough, it's as run-of-the mill as something as iron. To a star, iron is the most dangerous element in the universe. It's poison. Iron absorbs energy. From the moment a massive star creates iron, it has only seconds to live. The star is trying to dump energy into that iron ball and trying to make it fuse, but it can't. And so that ball is robbing the star of energy, and it's that energy that is supporting the star itself. So, as soon as that iron starts to be created in the core, the star has written its own death sentence. The battle between gravity trying to crush the star and fusion trying to blow it apart is over. With iron, fusion hits a dead end. Gravity always wins. The iron core collapses. The outer layers of the star slam down into it, and a huge explosion is generated. It's the single most violent event in the universe -- a supernova. In just a few seconds, supernovas create more energy than our sun ever will. Within a couple seconds after beginning to make iron, the star explodes in a supernova. So, think about that when you're holding one of your iron frying pans. The iron killed a star in just a few seconds -- dangerous stuff."
"A critical situation arises when iron accumulates in the core, since iron nuclei are incapable of generating further energy through fusion." en.wikipedia.org/wiki/Chandrasekhar_limit
"The first type of supernova happens in binary star systems. Binary stars are two stars that orbit the same point. One of the stars, a carbon-oxygen white dwarf, steals matter from its companion star. Eventually, the white dwarf accumulates too much matter. Having too much matter causes the star to explode, resulting in a supernova. The second type of supernova occurs at the end of a single star’s lifetime. As the star runs out of nuclear fuel, some of its mass flows into its core. Eventually, the core is so heavy that it cannot withstand its own gravitational force. The core collapses, which results in the giant explosion of a supernova. The sun is a single star, but it does not have enough mass to become a supernova." www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-a-supernova.html