An article accepted for publication in “The Astrophysical Journal” reports the discovery of a type Ia supernova, cataloged as SN 2015 cp. A team of astronomers led by Melissa Graham of the University of Washington used observations made with the Hubble Space Telescope and others to study a binary system in which a star that could be a red giant ejected huge amounts of materials and a part reached its companion, a white dwarf, causing its explosion.