New light shed on how stardust forms around the remnants of a supernova
By Anthony Wood
July 13, 2014
Using an instrument mounted on the European Southern Observatory's (ESO's) Very Large Telescope (VLT), scientists have been able to shed light on some of the mysteries surrounding stardust by observing the event and aftermath of a supernova. The observation was undertaken in an attempt to answer a number of questions regarding stardust, chief of which being where and how the grains are formed and grow. Another oddity that the team hoped to resolve was just how these tiny, fragile particles manage to survive the inhospitable environment that prevails following a supernova.
The team imaged the remains of the gigantic explosion from the supernova SN2010jl in visible and near infrared wavelengths via the X-shooter medium resolution spectrograph mounted aboard the VLT at the Paranal Observatory, Chile. In total, 10 observations were made of the aftermath of the supernova.
"By combining the data from the nine early sets of observations we were able to make the first direct measurements of how the dust around a supernova absorbs the different colors of light," says Christa Gall from Aarhus University, Denmark and lead author of the paper. "This allowed us to find out more about the dust than had been possible before."
It was discovered that the stardust produced by the death of SN2010jl came about in two distinct phases. The first stage began soon after the explosion, with the early grains coalescing inside the densest clouds of material created by the dying star. These particles were relatively large for stardust, measuring over one thousandth of a millimeter. The sizable nature of these early particles may at least in part explain how the dust was able to survive the inhospitable post supernova environment. However, the creation of stardust this size so soon after the death of SN2010jl raises questions of their own.
"Our detection of large grains soon after the supernova explosion means that there must be a fast and efficient way to create them," says Jens Hjorth, Professor at the Niels Bohr Institute of the University of Copenhagen. "We really don’t know exactly how this happens."
The second creation phase took place several hundred days after the supernova event. These later particles formed around the star from material that was initially thrown off before the star went supernova. This discarded material then coalesced into a shell shaped cloud of cool gas by the shock wave from the resultant explosion.
"Previously astronomers have seen plenty of dust in supernova remnants left over after the explosions," says Gall. "But they also only found evidence for small amounts of dust actually being created in the supernova explosions. These remarkable new observations explain how this apparent contradiction can be resolved."