All the way back in January, I had the great fortune to attend the American Astronomical Society’s (AAS) conference in Long Beach, California. I had a lot of fun. However, between the free beer and desperately searching for wireless Internet signal, I also did some work. During my travels, I spent some time browsing the poster sessions, trying to get inspiration for an article or two. You’d think that when presented with hundreds of stunning posters that inspiration wouldn’t be that far away. However, I was repeatedly frustrated by information overload and defaulted to a clueless meander up and down the pathways walled with intense science debates.
But then I saw it, right at the end of one of the poster walls, a question that got my imagination bubbling: “Will The Sun become a Metal Rich White Dwarf After Post Main Sequence Evolution?” The Sun? After the Main Sequence? Metal rich? To be honest, these were questions I’d never really pondered. What would happen when the Sun turns into a white dwarf? Fortunately, I had Dr John Debes to help me out with the answers…
Cutting to the chase, dusty white dwarf stars are a mystery. Astronomers have observed them for some time, and they are pretty obvious when the light from the white dwarf is analysed. Absorption lines in the white dwarf spectra show the presence of dust. Current theories suggest this dust is there after rocky debris (i.e. asteroids) fall too close to the white dwarf, and through tidal shear get shredded (like what happened when comet Shoemaker-Levy 9 strayed too close to Jupiter and got ripped apart by its gravity). The rock is then pulverized over millions of years and the dust eventually settles into the white dwarf.
Sounds reasonable, but what mechanism(s) feeds the white dwarf with asteroids over long time-scales? This is where John Debes’ work is very insightful. In his model, Debes simulates an evolved Solar System. This means the Sun has run out of hydrogen in its core in 4-5 billion years time, puffed up into a huge, angry red giant (eating up all the inner planets, from Mercury to the Earth), and then ejected its plasma into space, forming a vast planetary nebula. What is left behind is a white dwarf where the Sun used to be and the outer planets are orbiting at an expanded distance from the Sun. Like now, Jupiter will still wield its gravitational dominance, influencing the gravity of the asteroid population continuing to orbit the dense white dwarf Sun.
Using derived asteroid accretion rates from observations of dusty white dwarfs, Debes is currently working out whether his model can explain the mechanism behind dusty white dwarfs, and the possible mechanism that will make our Sun a future dusty white dwarf. Naturally, this is very exciting, as if Jupiter’s influence on the Solar System’s asteroids is enough to explain the observed accretion rates, could it mean that we are observing white dwarfs with massive Jupiter-like gas giants shepherding asteroids closer to the host white dwarf? Also, does this mean that we could be observing white dwarfs that give us a glimpse of what our Solar System may look like in a few billion years? Possibly.
All going well with Debes’ model, more results will be forthcoming, and I look forward to reading any further papers on the subject. A big thank you to John Debes for taking the time to explain his work to me. It turns out that although I couldn’t digest all the posters being presented at the AAS, I find one piece of research that captivated my imagination so much, I didn’t need any more…
For more, check out my Universe Today article “The Sun as a White Dwarf Star“