Image Credit: NASA/Hubble Space Telescope
An international group of astronomers, directed by scientists from Swinburne University of Technology, has found proof that the Universe broke its increasing 'fever' about 11 billion years ago. They calculated the temperature of the Universe when it was 3 to 4 billion years old by reviewing the gas among galaxies – the interstellar medium. Throughout these initial years of the Universe's expansion, numerous tremendously active galaxies were 'switching on' for the first time and warming their surroundings.
Lead scientist Elisa Boera, a PhD student from Swinburne's Centre for Astrophysics and Supercomputing, said "The intergalactic medium is an excellent recorder of the Universe's history. It retains memory of the big events that affected its properties, such as temperature and composition, during its different phases of evolution."
A previously study found that the Universe held this fever early in its history. Its writers used a new 'thermometer' – the imprint left on the light by the interstellar medium as it journeyed to Earth from distant, tremendously bright things called quasars.
In the new study, Ms Boera composed the bluest light that Earth's atmosphere conveys, harsh ultraviolet (UV) light from 60 quasars, and used the same technique as the previous study. This UV light originates from somewhat later in the Universe's expansion, allowing the fresh temperature measurement.
The finding has been printed in the Monthly Notices of the Royal Astronomical Society.
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