Free Astronomy Magazine March-April 2015

STELLAR EVOLUTION LBV. The less massive one, Eta Cari- nae B, seems instead to be a young blue-white star of spectral type O, thus with a photosphere significant- ly warmer (around 30,000 kelvin). Also due to the fact of having in the past been considered (when it was believed to be single) the best candi- date for the next galactic supernova role, Eta Carinae has been studied with particular attention by astrono- mers, who proposed several models aimed at interpreting its behaviour and describing its evolutionary past and future history. The knowledge acquired on that star system was merged into a long study conducted by researchers at NASA's Goddard Space Flight Center, who, under the coordination of the astro- physicist Ted Gull, monitored Eta Ca- rinae for over a decade, using space and ground-based telescopes. At the last meet- ing of the American Astronomical Society held in Seattle, Gull and colleagues took stock of the current understanding of the sys- tem at issue, describing a scenario that con- vincingly construes the turbulent variability T he animation on the side shows the vari- ability of the emission of dou- bly ionized iron (4659 ångström) in the Eta Cari- nae system be- tween 2010 and 2014. Below, a 3-D reconstruc- tion of the nebu- la of gas and dust created as a result of the 19 th century stellar eruptions. [NA- SA's Goddard Space Flight Cen- ter/T. Gull et al.] observed to date. Although the causes of the past impressive eruptions remain so far obscure, light has been shed on other phe- nomena thus far unclear, mostly related to the passage at the periastron of Eta Carinae B; namely, a marked variability in the emis- sion of X-rays, along with the appearance- disappearance of structures and sig- nals spatially very close to the stars and detectable at specific wave- lengths of the visi- ble light. In having been able to directly fol- low 3 periastron passages, the GSFC team could enter a sufficient amount of data into a nu- merical model and start a complex sim- ulation in order to understand the structures current- ly visible and pre- dict the behaviour of the system dur- ing the next peri-