Free Astronomy Magazine March-April 2015

astron event in 2020. The results of this work, published in the Monthly Notices of the Royal Astronomical Society, show that the periodic changes observed in the system of Eta Carinae are largely attributable to the interaction between the raging winds blowing from the photospheres of the two stars and that these winds have very differ- ent properties. In fact, those produced by Eta Carinae A are much denser and slower than those of its companion: in the first case they blow at a speed of 1.6 million km/h, tearing off from the star the equiva- lent of 1 solar mass every millennium; in the second case the material dispersed into space is 100 times less abundant, but the speed of its winds is nearly 10 million km/h. The simulations set up by Thomas Madura (GSFC) were processed with the Pleiades su- percomputer of the NASA’s Ames Research Center (Moffett Field, California) and reveal the full complexity of the interaction be- tween the winds. When Eta Carinae B ap- proaches the periastron and hurtles around Eta Carinae A, the relentless winds of the former carve a tunnel in the more dense outflow of the latter. The signs of this tran- sit remain visible in the form of spiralling structure for a decade (given that the gas gradually moves away from the primary), thus allowing to investigate the properties of that phenomenon during the previous two periastron passages. To better visualize the effects of the inter- action between the winds, Madura created some 3-D models of the simulations by pro- A 3-D visualiza- tion of the spiralling tunnel dug by Eta Cari- nae B’s wind in the shell of gas fed by Eta Carinae A’s wind. The many spike-like protrusions pre- dicted by the model employed are not yet con- firmed in reality. [NASA's Goddard Space Flight Cen- ter/T. Gull et al.]