A team of astronomers led by Christina Gall, an astrophysicist at Aarhus university, have made significant progress in answering a fundamental question regarding the development of the modern universe; the origins of cosmic dust. Contrary to previous observations of supernovas, new data tracking the supernova over a much longer period of weeks to years, the researchers were able to detect a phase during which large particulate matter on the order of microns were being ejected from the remnant of the star.
Cosmic dust is a pervasive, quintessential component of the universe; it provides the raw ingredients for new stars, planets and ultimately, life itself. Until recently, scientists could not account for its abundance; it was unclear where or how the volume required for the contemporary universe could have formed in such quantities among frenetic star production in young galaxies. One posited idea was that cosmic dust was formed and ejected into space during violent supernova – but previous observations suggested such events produced far too little material to account for the abundance in the early universe.
Gall’s team observed the spectral changes of the nearby supernova remnant SN2010jl using the Very Large Telescope (VLT) on Cerro Paranal, Chile, to discern its constituents. They monitored developmental changes from just several weeks post supernova over a period of years. In doing so, Gall’s team identified distinct phases of dust production. Between days 40 and 240, large volumes of cosmic dust were shown to be present, however, models suggested this particulate matter, if ejected during the supernova itself, would not have had sufficient time to cool and condense. Instead, Gall suggests the dust must have had to have been ejected prior to the supernova, as instability tore through the dying star. After the star went supernova, the shockwave passing through the ejecta compressed the dust into a “shell”, providing a more conducive environment for gravity to take over and the particulate matter to begin coalescing.
In the earlier phase of the study, the VLT showed large dust grains present – from 1 to 4 micrometers across – their size providing the capacity to “make them resistant to shocks associated with the supernova slamming into the interstellar medium”. Observations also showed that while slow at first, dust production began to speed up as the supernova remnant aged, lending further credence to the hypothesis that the supernova shockwave itself acted as a catalyst for grain formation. Longer term observations – between days 500 to 868 showed that as higher elements began to cool, cosmic dust production accelerated, rising ten-fold. By day 868, the mass of cosmic dust produced was equivalent to 0.0025 solar masses – or – 830 Earths.