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Ted Gull: Eta Carinae is one of the most
intriguing sources in the sky. And there's actually a large group of us
around the world that are keenly interested in it.
Tom Madura: Eta Carinae is one of the most massive stars in the galaxy, and it is also
a very evolved massive star that we think is near the end of its
lifetime. It is believed to be about 90 solar
masses, and it was thought to be a single star star for the longest time,
but it turns out that we know that it is actually a binary system and there is a second
star that we believe to be about 30 solar masses that exists
in the system. In the 1840s, Eta Carinae
experienced what we call the "Great Eruption" where it blew out somewhere between
10 and 40 times the mass of our sun in material.
And that material formed this nebula that now surrounds the system.
Ted: The nebula itself is a little bit large to map completely by Hubble,
and actually we did that a long time ago with the Space Telescope Imaging Spectrograph
However, we were only able to see evidence of the
dust, dusty regions. Tom: So, the thing that we did is
we had a international collaboration, and we used the
Very Large Telescope, in Chile, to do
spectroscopic mapping of the entire Homunculus Nebula, and what makes
our mapping unique is that previously only about
five slits had been used to map the entire Homunculus
whereas we used closer to 100 slits across the entire
length of the nebula to map everything including very small details.
This is one of the first times we not only have a 
3D model for an astrophysical object, but we were actually able to take our
3D model and print it on a 3D printer.
Ted: What we find here is that there's dimples in the two lobes:
here in the blue shifted--that which is approaching us--and in the red shifted
section here. And then most peculiarly, in between, 
where we might expect to see something fairly symmetrical around here, we see
these two wings coming out, tilted both with respect to the
bi-polar structure and with respect to the orbit of the two stars.
Tom: That gives us very important information
about the physical mechanisms that are responsible for forming the 
nebula. For example: trying to determine whether or not it was a single
star that had an explosion, or if the binary had some
important effect on shaping the nebula. Ted: This new model tells
us that, potentially, the explosive event happened
when the stars were closest to each other, and that
the material that came out not only came out in the polar regions
but was shaped in the orbital plane, which is between
these two systems. It tells us that the explosion event
probably started on one side of the star and then propagated elsewhere.
Tom: Prior to these observations and the modeling, there was no
reason to think that binarity played any role
in the eruption or the forming and shaping of the homunculus.
But now that we have this more detailed model, it turns out that the
distance between each of these features is very similar to
measurements of the central binary, and so for the first time,
we have evidence that binarity played a role
either in the Great Eruption itself, or in shaping
the nebula after the initial explosion.
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