The number of ways stars can find to die bizarre deaths will never cease to amaze me.
Some explode, supernovae which blast radiation across the Universe. Others fade away slowly over hundreds of billions of years, longer than the cosmos has been around. Some blow off winds of gas and dust, taking on strange shapes from perfect spherical shells to elongated structures that look like two jellyfish kissing.
And then some – a very few – are like R Sculptoris, a red giant on the thin hairy edge of death. And its death is both spectacular as well as just plain old damned weird.
Check THIS out:
This is not a drawing! It’s actual data, observations of R Sculptoris made using the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA looks at light far too low energy for our eyes to see; it’s actually out past infrared in the spectrum. Cold dust and gas emits light at this wavelength, including carbon monoxide. That molecule is created copiously in red giants and shines brightly in the submillimeter, making it easy to see with ‘scopes like ALMA. That’s nice, because CO can be used as a tracer for other, harder to detect molecules like hydrogen. Looking at CO really tells you a lot about what’s going on in the gas and dust.
And what’s going on? Ah, this is the really cool part.
When a star like the Sun (either a bit less massive, or up to about 8 times as massive) ages, the core heats up, which causes the outer part of the star to expand (like a hot air balloon), turning it into a red giant. The details are complicated – read this post on a similar star where I explain it in more detail (and you want to because the details are awesome) – but the bottom line is that helium builds up in a thin shell outside the star’s core, where it fuses into carbon. The fusion rate is insanely sensitive to temperature, and periodic imbalances in temperature cause vast and very sudden increases in the fusion rate – and by sudden I mean over a timescale of just a handful of years, the blink of an eye to a star. Called a thermal pulse, this huge fireball of energy is dumped into the star’s interior, blows upward like a tsunami, and then blasts material clear off the star’s surface.
The result is an epic paroxysm which blows out a massive wave of material, expanding in a sphere around the star. We’ve seen this before, like in the star U Cam. After a few years, you get an eerie detached shell of expanding material, like a smoke ring trillions of kilometers across.
OK, so that’s the thin shell thing on the outside. So what’s the deal with R Sculptoris that makes that freaky inner spiral pattern?