Explosive Origin of Cosmic
Dust Discovered
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The first definitive evidence of cosmic dust, important in building planets like
our Earth and ultimately ourselves, has been found in the remains of a
massive star explosion 11,000 light years away in our own Galaxy.
Cosmic dust is made up of tiny particles of solid material and is present
throughout the cosmos. It helps developing stars to ignite and also forms the
matter making up planets and all living creatures - but there has been
controversy over where it is formed.
Scientists have long suspected that exploding stars, or supernovae, are an
important source of cosmic dust, but now an international team including a
Cardiff University astronomer has provided unambiguous proof.
Dr Haley Gomez, of the University’s School of Physics and Astronomy, played
a part in analysing images from NASA’s Spitzer Space Telescope of the
remains of the supernova Cassiopeia A (Cas A).
Cas A would have been 30 times the mass of our own Sun but would have
taken just 10 million years to reach the explosion stage, providing a rapid
source of dust.
Dr Gomez was part of a team of UK astronomers who had previously hunted
for dust grains in this enigmatic object.
In this previous work, although dust was detected in Cas A, it was difficult to
pinpoint where exactly it was coming from - whether it was made in the
supernova or elsewhere.
Using Spitzer’s sensitive infrared detectors, the international team led by Dr
Jeonghee Rho from NASA's Spitzer Science Center, have now found enough
cosmic dust in Cas A to make up 10,000 Earths.
Scientists found the cosmic dust was made up of proto-silicates, silicon
dioxide, iron oxide, pyroxene, carbon, aluminium oxide and other compounds,
all located in the same place as the supernova gas.
"Now we can say unambiguously that dust - and lots of it - was formed in the
ejecta of the Cassiopeia A explosion,” Dr Rho said.
However, the findings from the Spitzer telescope do not explain where all of
the dust seen in distant galaxies comes from. Cardiff astronomers are now
working on cameras for the new European Herschel Space Telescope which
could provide a final answer.
“At the moment we’re missing something. The dust Spitzer is looking at is
quite warm - about 100 degrees Kelvin. We think there’s colder dust in there,
which Spitzer doesn’t see - at around 20 degrees Kelvin. We’re hoping that
Herschel will allow us to see the colder dust. Herschel could completely
change the way we see the Universe,” said Dr Gomez.
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