We are stardust and life is a blast

Planet Earth – and all life on it – had an explosive start, scientists revealed today. They have found conclusive evidence that the cosmic dust from which everything is made came from old stars that blew themselves to pieces – an event called a supernova.

An international team of astronomers studied the remains of one massive stellar explosion, called Cassiopeia A, 11,000 light-years away.

Using Nasa’s Spitzer space telescope, they found enough cosmic dust from the blast to make up 10,000 planets the size of the Earth.

Astronomers had long appreciated that cosmic dust spread throughout the universe helps new stars to start burning and form solar systems. But there was controversy over its origins.

Dr Haley Gomez, of Cardiff University’s School of Physics and Astronomy, was part of the team that analyzed images from the heat-seeking Spitzer telescope of Cas A. The space observatory’s sensitive infrared detectors revealed conclusively that the dust grains came directly from the supernova blast.

The research showed that Cas A was once 30 times the mass of our own Sun but took just 10 million years to reach the explosion stage, when it provided a rapid source of dust. The dust grains were found to be 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.

Team leader Dr Jeonghee Rho, of Nasa’s Spitzer Science Centre, said: “Now we can say unambiguously that dust – and lots of it – was formed in the ejecta of the Cassiopeia A explosion.”

The scientists say that the dust they observed is relatively warm (100 degrees Kelvin, or minus 173 degrees Celsius) and so they have been unable to confirm the origin of much colder dust (20 degrees Kelvin or minus 253 degrees C) seen in distant galaxies. Cardiff scientists are working on cameras for a powerful new European space telescope, called Herschel, which is due for launch in July.

Dr Gomez said: “At the moment we’re missing something. The dust Spitzer is looking at is quite warm. We think there’s colder dust in there, which Spitzer doesn’t see. We’re hoping that Herschel will allow us to see the colder dust. Herschel could completely change the way we see the Universe.”

The team’s discovery that we are stardust will be published in the Astrophysical Journal.

Picture: This Nasa image combines observations made with the Spitzer, Hubble and Chandra space telescopes.

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