Free Astronomy Magazine September-October 2015

SPACE CHRONICLES First detection of lithium from an exploding star by ESO T he light chemical element lith- ium is one of the few elements that is predicted to have been created by the Big Bang, 13.8 billion years ago. But understanding the amounts of lithium observed in stars around us today in the Universe has given astronomers headaches. Older stars have less lithium than ex- pected, and some younger ones up to ten times more. (More precisely, the terms “younger” and “older” are used to refer to what astronomers call Population I and Population II stars. The Population I category in- cludes the Sun; these stars are rich in heavier chemical elements and form the disc of the Milky Way. Population II stars are older, with a low heavy- element content, and are found in the Milky Way Bulge and Halo, and globular star clusters. Stars in the “younger” Population I class can still be several billion years old!) Since the 1970s, astronomers have speculated that much of the extra lithium found in young stars may have come from novae — stellar ex- plosions that expel material into the space between the stars, where it contributes to the material that builds the next stellar generation. But careful study of several novae has yielded no clear result up to now. A team led by Luca Izzo (Sapienza University of Rome, and ICRANet, Pe- T his image from the New Technology Telescope at ESO’s La Silla Ob- servatory shows Nova Centauri 2013 in July 2015 as the brightest star in the centre of the picture. This was more than eighteen months after the initial explosive outburst. This nova was the first in which evidence of lithium has been found. [ESO]