Free Astronomy Magazine September-October 2018

18 SEPTEMBER-OCTOBER 2018 SPACE CHRONICLES Stellar corpse reveals origin of radioactive molecules by ESO A rtist impression of the collision of two stars, like the ones that formed CK Vulpeculae The inset illustrates the inner structure of one red giant before the merger. A thin layer of 26-aluminium (brown) surrounds a helium core. An ex- tended convective envelope (not to scale), which forms the outermost layer of the star, can mix material from inside the star to the surface, but it never reaches deep enough to dredge 26-aluminium up to the surface. Only a collision with an- other star can disperse 26-aluminium. [NRAO/AUI/NSF; S. Dagnello] A team of astronomers led by Tomasz Kami ń ski (Harvard- Smithsonian Center for As- trophysics, Cambridge, USA), used the Atacama Large Millimeter/sub- millimeter Array (ALMA) and the NOrthern Extended Millimeter Array (NOEMA) to detect a source of the radioactive isotope aluminium-26. The source, known as CK Vulpecu- lae, was first seen in 1670 and at the time it appeared to observers as a bright, red “new star”. Though ini- tially visible with the naked eye, it quickly faded and now requires