NASA’S GODDARD SPACE FLIGHT CENTER/T. MADURAThe stars of Eta Carinae (dark spots): the smaller of the two may be losing massNASA’S GODDARD SPACE FLIGHT CENTER/T. MADURA
Recent observations suggest that something strange is going on with the smaller star in Eta Carinae, a stellar system of two giant stars – one being 90 times as massive as the Sun, and the other 30. Located 7,500 light-years from Earth, in the southern constellation Carina, visible to the right of the Southern Cross, the system is one of the most mysterious in the Milky Way. Every five and a half years, Eta Carinae goes dark for approximately 3 months on certain wavelengths of the electromagnetic spectrum, especially the X-ray frequencies. The most recent blackout was seen in the second half of 2014 and was analyzed in depth by international teams of astronomers. A study presented in January 2015 in Seattle, at the 225th Meeting of the American Astronomical Society, suggests that the secondary (smaller) star may be losing mass, causing an observable alteration in the system. “The data indicate that the intensity of emissions produced by doubly ionized helium (He II) have not changed in the past five and a half years, but the X-ray emissions have increased systematically over the past 16 years,” says Brazilian astrophysicist Mairan Teodoro, a researcher at Western Michigan University and one of the authors of the study. In principle, the increase in X-ray emissions could be explained by variations in a given parameter of either of the two stars. However, Teodoro and his colleagues have evidence that the alteration is associated with ongoing modifications to the secondary star. The researchers believe that the increase in X-rays may be caused by an intensified rate of mass loss by the smaller star of Eta Carinae. But their hypothesis is still pending confirmation.
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