Using the MPG/ESO 2.2-m telescope at the La Silla Observatory and the ESO 0.5-m telescope at the Observatory of the Pontificia Universidad Catolica de Chile near Santiago, Chile, astronomers have detected the chemical element lithium in the material ejected by a nova, a star that suddenly increases in brightness by several magnitudes. The finding could help explain the mystery of why many young stars seem to have more lithium than expected.
This image shows Nova Centauri 2013 (brightest star in the center) in July 2015. This was more than eighteen months after the initial explosive outburst. Image credit: ESO.
Lithium 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 this element observed in stars around us today in the Universe has given scientists headaches.
Older stars (Population II stars) have less lithium than expected, and some younger ones (Population I stars) up to 10 times more.
Since the 1970s, astronomers have speculated that much of the extra lithium found in young stars may have come from novae – stellar explosions that expel material into the space between the stars, where it contributes to the material that builds the next stellar generation. But of several novae has yielded no clear result up to now.
Now, Dr Luca Izzo from the Sapienza University of Rome and his colleagues have used ESO’s telescopes in Chile to study a nova called the Nova Centauri 2013.
The star, also known as V1369 Centauri, exploded in the southern skies close to the bright star Beta Centauri in December 2013 and was the brightest nova so far this century.
The new data revealed the clear signature of lithium being expelled at 2 million km per hour from the star.
“It is a very important step forward. If we imagine the history of the chemical evolution of the Milky Way as a big jigsaw, then lithium from novae was one of the most important and puzzling missing pieces,” said team member Dr Massimo Della Valle from the INAF-Osservatorio Astronomico di Capodimonte, Naples, and ICRANet, Pescara, Italy.
“In addition, any model of the Big Bang can be questioned until the lithium conundrum is understood.”
The mass of ejected lithium in Nova Centauri 2013 is estimated to be tiny, but, as there have been many billions of novae in the history of our Milky Way Galaxy, this is enough to explain the observed and unexpectedly large amounts of lithium in the Galaxy.
“It is very exciting to find something that was predicted before I was born and then first observed on my birthday in 2013,” Dr Izzo said.
The results were published online July 17 in the Astrophysical Journal Letters (arXiv.org preprint).
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Luca Izzo et al. 2015. Early Optical Spectra of Nova V1369 Cen Show the Presence of Lithium. ApJ 808, L14; doi: 10.1088/2041-8205/808/1/L14
