Since Centaurus A is about 15 million light - years away from us , this supernova happened 15 million years ago .
Its host galaxy , Centaurus A , is about 15 million light - years away in the constellation Centaurus .
Since Centaurus A   is about 15 million light - years away from us , this supernova happened 15 million years ago .
Its host galaxy , Centaurus A , is about 15 million light - years away in the constellation Centaurus .