[ngcles]

Hi All,

Like a great number of other amateurs, I've been keeping one eye on Eta Carinae ever since it broached naked-eye visibility again.

The events to which the telegram refer are very likely due to interactions between the winds between the two stars as they approach periastron (ie one solar-wind colliding with the other). These events are really largely observable at very high energies (hard x-ray & gamma rays). The cause of these events is almost certainly extrinsic to the stars themselves (external). Sure, take spectra, but don't be too disappointed if it shows little or nothing.

Eta has been slowly climbing in visual magnitude for a long time but its output measured over all wavelengths (bolometric magnitude) is nearly unchanged for quite a while (decades). When I did an estimate the other night, I put it at 4.4 and this has been pretty constant for the last several years.

So while the star's(s) overall output is fairly constant, what has changed is the wavelengths of peak emission. The currently accepted explanation, or at least the "best model" is that the Homunculus Nebula, likely ejected during the 1890s event has expanded sufficiently and lowered in density and temperature sufficiently that the star itself is shining "out" of the nebula as opposed to "through" the nebula (ie light from the star(s) absorbed by the nebula and then re-emitted at a different wavelengths). While the visual output has been climbing, the infra-red emission has been generally falling. That is similarly reflected in the changing nature in the appearance of the homunculus at visual wavelengths that has been apparent over the last 30-40 years -- more particularity during the last 20 years.

It is all rather intriguing, but I wouldn't be reading too much into its increasing brightness at visual magnitudes which is most likely due to the binary "clearing-out" their immediate neighbourhood(s).

That's not to say: "nothing is about to happen here, return to your beds good citizens". It might well do in a way that isn't predictable, but the current observed changes don't actually say much about the internal composition or structure of the stars where the "real action" will take place when/if does go kahblooie.

Best,

L.