Astronomers watching a supernova may have found out where the star dust that made up much of our Universe came from.
Star dust, also known as cosmic dust, contains many of the elemental ingredients needed for life, including carbon, oxygen and nitrogen, and also plays a role in the birth of stars and rocky planets. It's of great significance to our existence, but until recently, no one has been sure of where it comes from, or how it's produced in quantities large enough to form entire universes, specifically ours.
In the past, astronomers have proposed that star dust was produced as a side effect of supernova explosions - which is how large stars die - but there didn't seem to be enough supernovae near our galaxy to produce all the star dust in our Universe.
In a paper published in Nature, a team of astronomers has reported witnessing the formation of star dust in a supernova called SN 2010jl, and watched as the star dust continued to form over an extended period of time after the explosion, from just a few weeks to 2.5 years afterwards.
They observed the supernova using a spectrograph on the Very Large Telescope in Chile, which allowed them to measure the visible light absorbed by the star dust particles, plus the infrared radiation that they gave off.
Because previous studies on star dust formation had only looked at supernovae for a short period of time before moving on, “they did not tell us the full story of how much dust supernovae produce”, one of the team, Christa Gall, an astrophysicist at Aarhus University in Denmark, told Roy Cowen at Nature Magazine.
The team reported that the star dust that was present between 40 and 240 days after the supernova explosion, and consisted of material that the dying star expelled just before it turned into a supernova. They also found that these particular star dust particles were relatively enormous, measuring 1 to 4.2 micrometres across, which is at least four times the size of a regular star dust particle.
"It is harder to form large dust particles, notes Gall, but their size makes them resistant to destruction by shocks associated with the supernova slamming into interstellar material, and probably accounts for their longevity," says Cowen at Nature Magazine.
The amount of star dust generated by supernova SN 2010jl started off small, but between 500 and 868 days after the explosion, the amount really ramped up. The researchers suggest that this marks a second phase in supernova dust production, which occurs when the debris generated from the explosion has cooled down.
"At day 868, the last time Gall’s team observed the supernova, the amount of dust had increased to 0.04 of the Sun’s mass, or 830 Earth masses,” says Cowen at Nature Magazine. "If the increased dust production continues, in 20 years SN 2010jl will have produced the equivalent of half the Sun’s mass in dust particles, similar to the amount observed in the widely observed supernova SN 1987A.”
This means that if there were a number of supernovae active around the time our Universe was still young, and they were producing star dust at the same rate as SN 2010jl and supernova SN 1987A, they could certainly have provided all the dust we know was present in the formation of our Universe.
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