An image of LX Cyg and its surroundings, obtained with the 80cm telescope at the University of Vienna Observatory. Credit: Stefan Uttenthaler et al./University of Vienna
A carbon star is a giant red star nearing the end of its life, with an atmosphere containing more carbon than oxygen. LX Cygni could be an interesting example of an object that is currently in the process of transitioning into a carbon star. “These observations are important to understand the chemical evolution of the universe, because most of the carbon in the universe is thought to come from stars just like LX Cygni,” Uttenthaler said.
Most of the carbon in our bodies comes from an earlier generation of stars such as LX Cygni. We are literally stardust!” Uttenthaler and his colleagues noted that carbon stars are a special class of stars that have a chemical composition that is distinct from that of other stars throughout the universe. In most stars, including our sun, oxygen is more abundant than carbon, as measured by the carbon/oxygen ratio. LX Cygni as it is a rare case of a star enabling observations of stellar evolution in real time which may lead to unique insights into the transition from oxygen rich to carbon-rich stars.
The researchers obtained optical high- and low-resolution spectra as well as mid-resolution infrared spectra to investigate LX Cygni’s spectral features. These observations indicated a dramatic increase of the star’s pulsation period in recent decades so the scientists concluded that LX Cygni appears to undergo an important transition in its evolution. They believe that is related to a process that brought up carbon from the interior of the star and a genuine abundance change happened. It must have happened quickly when compared to other processes in a star’s lifetime.”The whole process seems to have taken only some 30 years,” Uttenthaler said.
What is interesting is that LX Cygni’s transition process may be already completed. The observations conducted in 2008, using NASA’s Spitzer telescope, suggest that LX Cygni was a carbon star at that time. To resolve all the uncertainties, Uttenthaler’s research team recommends that the community continues observing this star, most importantly to conduct observations in the mid-IR and in the radio regime to study the dust and molecular composition of the circumstellar envelope of LX Cygni.
“From this, we would learn what the chemical composition and the mass-loss rate of the star was in the past, how the dust and molecular inventory of the star evolved over the past few thousand years. This would be extremely interesting to know!” Uttenthaler said. https://www.eso.org/sci/meetings/2015/Steps2015/Poster_files/Uttenthaler_STEPS2015_poster2.pdf
http://phys.org/news/2015-11-stardustcarbon-star-lx-cygni-insights.htmljCp
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