Alpha and Beta Centauri, two of the brightest stars in the southern sky, gained a new companion in late 2013 — the naked eye Nova Centauri 2013. The iconic Southern Cross lies at the top center. This photo was captured by ESO Photo Ambassador Yuri Beletsky at ESO’s La Silla Observatory in the Chilean Atacama Desert during the morning of Monday, December 9, 2013. Image credit: Y. Beletsky (LCO)/ESO. The chemical element lithium was discovered for the first time in material ejected by a nova. Observations of Nova Centauri 2013 using telescopes at ESO’s La Silla Observatory and near Santiago in Chile have helped to unravel the mystery behind why many young stars appear to possess more of this chemical element than anticipated. This new discovery fills a long-standing gap in the puzzle that represents our galaxy’s chemical evolution, marking a significant advancement for astronomers striving to comprehend the quantities of different chemical elements in Milky Way stars. Lithium, a light chemical element, is among the few elements predicted to have originated from the Big Bang approximately 13.8 billion years ago. However, understanding the observed amounts of lithium in stars within our Universe today has posed challenges for astronomers. Older stars exhibit less lithium than expected, while some younger ones show up to ten times more. Since the 1970s, astronomers have theorized that a substantial portion of the additional lithium present in young stars may have been sourced from novae — stellar explosions that release material into the interstellar space, contributing to the material that forms the subsequent generation of stars. Nonetheless, thorough examination of several novae has not yielded a definitive outcome thus far. A team led by Luca Izzo (Sapienza University of Rome and ICRANet, Pescara, Italy) utilized the FEROS instrument on the MPG/ESO 2.2-meter telescope at the La Silla Observatory, as well as the PUCHEROS spectrograph on the ESO 0.5-meter telescope at the Observatory of the Pontificia Universidad Catolica de Chile in Santa Martina near Santiago, to investigate the nova Nova Centauri 2013 (V1369 Centauri). This star underwent an explosion in the southern skies near the bright star Beta Centauri in December 2013 and stood out as the brightest nova in the 21st century — easily visible to the naked eye. This image from the New Technology Telescope at ESO’s La Silla Observatory depicts Nova Centauri 2013 in July 2015 as the brightest star at the center of the frame, more than eighteen months after the initial explosive event. This nova marked the first instance where evidence of lithium was identified. Nova Centauri 2013 is situated 11,000 light-years away. Image credit: ESO. The newly acquired detailed data unveiled a distinct signature of lithium being expelled at a speed of two million kilometers per hour from the nova. This marks the first detection of the element being ejected from a nova system to date. Co-author Massimo Della Valle (INAF–Osservatorio Astronomico di Capodimonte, Naples, and ICRANet, Pescara, Italy) elucidates the significance of this finding: “This is a crucial step forward. If we envision the Milky Way's chemical evolution history as a large puzzle, then lithium from novae was one of the most important and perplexing missing pieces. Furthermore, any model of the Big Bang can be called into question until the lithium enigma is unraveled.” The mass of ejected lithium in Nova Centauri 2013 is estimated to be minuscule (less than a billionth of the Sun's mass), yet given the numerous novae that have occurred throughout the Milky Way's history, this quantity suffices to account for the observed and surprisingly substantial amounts of lithium in our galaxy. Authors Luca Pasquini (ESO, Garching, Germany) and Massimo Della Valle have dedicated over a quarter of a century to searching for evidence of lithium in novae. This discovery is a gratifying conclusion to their prolonged quest. For the younger lead scientist, there is a different kind of excitement: “It is truly thrilling,” remarks Luca Izzo, “to uncover something that was predicted before my birth and then witnessed on my birthday in 2013!”
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