London:The universe is becoming gradually cleaner as more and more cosmic dust is being mopped up by the formation of stars within galaxies, an international team of astronomers has revealed. Peering back 12 billion years using the Herschel space telescope to produce far-infrared images of the sky, the team led by researchers at Cardiff University was able to observe the very early formation of galaxies and compare them to galaxies that have formed much more recently. "Our results show that the reason for this evolution is that galaxies used to contain more dust and gas in the past, and the universe is gradually becoming cleaner as the dust is used up," said co-leader of the project Steve Eales, Professor at Cardiff University's School of Physics and Astronomy. The findings were presented at the National Astronomy Meeting in Nottingham, Britain. Cosmic dust is comprised of tiny solid particles that are found everywhere in space between the stars. The dust and the gas in the universe is the raw material out of which stars and galaxies form. Though this blanket of material is key to the formation of stars and galaxies, it also acts as a sponge, absorbing almost half of the light emitted by stellar objects and making them impossible to observe with standard optical telescopes. The Herschel space telescope was launched in 2009 to provide researchers better tool for probing this hidden universe.