MYSTERIOUS GAS BULLETS DISCOVERED IN MILKY WAY'S ONLY KNOWN HELIUM NOVA

High-speed clumps of gas, possibly rich in oxygen, have been observed travelling at up to 20 million miles per hour from V445 Puppis, the Milky Way's only known helium nova, according to research presented at the Royal Astronomical Society's National Astronomy Meeting in Birmingham. John Mills, a doctoral student at the University of Warwick, made the discovery using observations from multiple telescopes spanning two decades. The debris cloud surrounding V445 Puppis, which obscured the stellar system at the turn of the century, has now cleared sufficiently to allow examination of the explosion's origin. The high-speed "bullets" have no known equivalent in other novae observed elsewhere in the universe, leaving their origin unexplained.

Mills's research confirms that V445 Puppis consists of a white dwarf—a dense stellar remnant—drawing material from a rare helium star in a binary system. A nova occurs when a white dwarf pulls gas from a nearby companion star; as this material accumulates on the white dwarf's surface, rising temperature and pressure trigger a thermonuclear explosion. Most known novae are fuelled by hydrogen-rich material, but helium novae operate differently, with the white dwarf accreting hydrogen-poor gas rich in helium, making such eruptions exceptionally rare and poorly understood. V445 Puppis has long been distinguished among novae for its complete absence of hydrogen, the most abundant element in the universe.

The confirmation of V445 Puppis's binary composition provides the first definitive characterisation of the stellar system responsible for the Milky Way's only currently confirmed helium nova. The discovery offers an unprecedented opportunity to study one of the rarest types of stellar explosions and to investigate the formation of the mysterious high-speed gas clumps. Further observations may help resolve the enigma of how such "bullets" are produced during helium nova eruptions.