Cosmic dust – it’s the stuff of planets, the building blocks of all solid things in the universe, right? Sure, but where, exactly, does it come from? That’s the questioned that has plagued scientists for decades, likely embarrassed by their inability to explain the most ubiquitous solid matter in the universe. Well, not science has something to be proud of: According to the Niels Bohr Institute at the University of Copenhagen, they’ve found the answer, and it lies in exploding supernovas.
“The problem has been that even though dust grains composed of heavy elements would form in supernovae, the supernova explosion is so violent that the grains of dust may not survive. But cosmic grains of significant size do exist, so the mystery has been how they are formed and have survived the subsequent shockwaves. Our research casts new light on this – both on how dust is formed and how it survives the shockwaves,” explains Professor Hjorth, head of the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.
Their research explains how the trace elements, originated in supernovas, eventually “clumps” into the aforementioned dust grains. As it turns out, it’s an issue of shock interaction: The first step is a small explosion, which releases a cloud of gas that then hangs around the star, growing stronger with subsequent explosions. When the star itself finally explodes, the shockwave hits the super-hot gas cloud at an astounding rate, compressing and cooling it down rapidly. At these cooler temperatures and higher densities, elements can nucleate and form solid particles.
The researchers explain how their equipment, including the X-shooter on the European Southern Observatory’s Very Large Telescope in Chile, helped unfold the mystery:
“Dust absorbs light and from our data we could calculate a curve that told us the about the amount of dust, the composition of the dust and the size of the dust grains. This showed something very exciting,” explains Christa Gall, a postdoc at Aarhus University and affiliated with the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.