Supernova expert Stan Woosley (University of California, Santa Cruz) is also skeptical of the high-mass claim. Extremely massive stars generally lose huge amounts of gas through stellar winds before they explode as supernova, especially when they are born in environments with relatively large amounts of elements heavier than hydrogen or helium (or metals, in astronomical parlance). That happens to be the case here: The accompanying star has some 20% more metals than the Sun.