Astronomers kind of live to see weird weird objects.
While likely always visible to humans, this southern hemisphere star transformed from kind of meh to the second brightest star in the sky during a dramatic event that was observed in 1840. It then faded entirely from the unaided-eye view before slowly increasing in brightness to be easily seen with the unaided eye.
I am totally here for stars being dramatic.
And when we look at Eta Carina with modern telescopes like Hubble, we find the eruption of 1840 led to one hell of a glowup.
Surrounding the point of light we see with our eyes is a remarkable, double-lobed nebula that we now understand is expanding away from not just one, but 2 stars.
And these stars are big: approximately 90 and 30 times the mass of the Sun…
And somehow, in 1840ish, they shed an even more remarkable 10-45 solar masses of material.
We don’t have a firm understanding of what happened, but with every passing year, we’re better able to say what resulted. This is because we can actually watch the nebula evolve over time. In a newly released video of data from the Chandra X-Ray observatory, for instance, we can watch how the nebula has expanded and the stars have together grown more luminous over the past 20 years.
The expanding ring we see in X-rays is actually large enough to surround the beautiful nebula Hubble sees. According to researcher Michael Corcoran, “We’ve interpreted this faint X-ray shell as the blast wave from the Great Eruption in the 1840s. It tells an important part of Eta Carinae’s backstory that we wouldn’t otherwise have known.”
Researchers now believe the Great Eruption consisted of 2 explosions. The first was made of low-density gas that expanded out, creating what we now see as an X-Ray ring, while the other was slower and made of the dense material that makes the visible nebula.
These observations are described in a new paper in the Astrophysical Journal that is led by Nathan Smith.
reference: Michael F. Corcoran et al 2022 ApJ 937 122 10.3847/1538-4357/ac8f27