天文学家在早期宇宙中发现尘埃

Dust plays an extremely important role in the universe -- both in the formation of planets and new stars. But dust was not there from the beginning and the earliest galaxies¹ had no dust, only gas. Now an international team of astronomers², led by researchers from the Niels Bohr Institute, has discovered a dust-filled galaxy³ from the very early universe. The discovery demonstrates that galaxies were very quickly enriched with dust particles containing elements such as carbon and oxygen, which could form planets. The results are published in the scientific journal, Nature. Cosmic dust are smoke-like particles made up of either carbon (fine soot) or silicates⁴ (fine sand). The dust is comprised primarily of elements such as carbon, silicon⁵, magnesium⁶, iron and oxygen. The elements are synthesised by the nuclear combustion⁷ process in stars and driven out into space when the star dies and explodes. In space, they gather in clouds of dust and gas, which form new stars, and for each generation of new stars, more elements are formed. This is a slow process and in the very earliest galaxies in the history of the universe, dust had not yet formed.   But now a team of researchers have discovered a very distant galaxy that contains a large amount of dust, changing astronomers' previous calculations of how quickly the dust was formed.   "It is the first time dust has been discovered in one of the most distant galaxies ever observed -- only 700 million years after the Big Bang. It is a galaxy of modest size and yet it is already full of dust. This is very surprising and it tells us that ordinary galaxies were enriched with heavier elements far faster than expected," explains Darach Watson, an astrophysicist with the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.   Darach Watson led the project, with Lise Christensen from the Dark Cosmology Centre and researchers from Sweden, Scotland, France and Italy.