After some elusive findings, evidence has finally come in of early Milky Way-size galaxies that are mature, leaving astronomers to wonder what caused them to grow up so quickly. Fifteen years ago, such galaxies were not predicted to even exist.
The mature galaxies were found at a record-breaking distance of 12 billion light years, seen when the Universe was just 1.6 billion years old. Their existence at such an early time raises new questions about what forced them to grow up so quickly.
“These distant and early massive galaxies are one of the Holy Grails of astronomy,” Director of the Centre for Astrophysics and Supercomputing at Swinburne University of Technology, Professor Karl Glazebrook, who was involved in the discovery, said.
“Fifteen years ago they were predicted not to even exist within the cosmological model favoured at the time. In 2004 I wrote a paper on the discovery of such galaxies existing only three billion years after the Big Bang. Now, with improved technology we are pushing back to only 1.6 billion years, which is truly exciting.”
Astronomers used deep images at near-infrared wavelengths to search for galaxies in the early Universe with red colours. These red colours indicate the presence of old stars and a lack of active star formation. Surprisingly, they located 15 galaxies at an average distance of 12 billion light years — only 1.6 billion years after the Big Bang.
These galaxies had already stopped forming stars when the Milky Way was only 12% of its current age.
See also: The Science Fictions series at your fingertips (cosmology).
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