The Universe broke its rising 'fever' about 11 billion years ago (w/ Video)

May 20, 2014 by Lea Kivivali

( —An international team, led by researchers from Swinburne University of Technology, has found evidence that the Universe broke its rising 'fever' about 11 billion years ago.

They measured the temperature of the Universe when it was 3 to 4 billion years old by studying the gas in between galaxies – the intergalactic medium. During these early years of the Universe's development, many extremely active galaxies were 'switching on' for the first time and heating their surroundings.

"However, 11 billion years ago, this fever seems to have broken and the Universe began cooling down again," lead researcher 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."

An earlier study found that the Universe caught this fever early in its history. Its authors used a new 'thermometer' – the imprint left on the by the as it travelled to Earth from distant, extremely bright objects called quasars.

In the new study, Ms Boera collected the bluest light that Earth's atmosphere transmits – harsh ultraviolet (UV) light from 60 quasars – and used the same method as the earlier study. This UV light comes from slightly later in the Universe's development, allowing the new temperature measurement.

An animation of the Universe's 'fever' breaking: As the UV light from powerful quasars ionizes the helium in the intergalactic medium, the gas heats up. But when all the helium is ionized, the quasar light can no longer heat the gas; it passes straight through and the gas begins to cool down as the Universe expands.

"The quasar light suggests that the Universe had cooled by about 1000 degrees C within 1 billion years after reaching its maximum of 13,000 degrees," Ms Boera said.

"This cooling trend has probably continued to the present day."

Why did the Universe's fever break?

"We think the answer is helium," co-author of the new study Swinburne Associate Professor Michael Murphy said.

"Fourteen per cent of the intergalactic gas is helium and, 12 billion years ago, it was absorbing the intense radiation from , losing electrons in the process.

"The electrons whizz around, heating up the gas. It's similar to the greenhouse effect on Earth: Carbon dioxide gas absorbs infrared radiation and heats our atmosphere.

"Once all the helium was ionized, the radiation would simply pass through the gas without heating it.

"Then, as the Universe expands the gas cools down, just like the cold sprayed from an aerosol can – it quickly cools as it expands out of the can."

The study has been published in the Monthly Notices of the Royal Astronomical Society.

Explore further: Spectrum of gamma-ray burst's afterglow indicates beginning of re-ionization process

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May 20, 2014
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Whydening Gyre
4.7 / 5 (14) May 20, 2014
Nothing more than a bunch of assumptions about their theoretical mumbo jumbo...

Which happens to be an assumption -on your part.
5 / 5 (10) May 20, 2014
It is not an "assumption" when you actually measure something as they did in this and prior studies.
5 / 5 (4) May 20, 2014
@cantdrive85 There is only one assumption, that the laws of physics were the same then as they are now. The measurements and reasoning in the article seem to be straight forward although thete is one point that I can't quite grasp.
@Whydening Gyre, you (or someone else following this) might be able to help me. Obviously we don't know what the condition is of distant QSO's is at this moment but if they heated gases to a certain temp wouldn't they continue to do this after cooling? Indeed would there a cooling at all so that the temp would rise and fall as the cooling and re-heating took place? Is it implied that QSO's would be moving away from a gas a such a rate that re-heating couldn't happen? Perhaps I have misunderstood; has the measurements been done on successive gases cominig into contact as QSO's moved away?
1 / 5 (7) May 20, 2014
Sub:Ignorance of the Worst Kind-Science at cross-purpose
Deliberate mis-lead and ignorance of the Worst kind-to save Big-Bang fever .How long this mischief can go without searching origins ? This mode self-defeats the purpose of Scientific Research. Need to search Cause and effect
not rated yet May 21, 2014
Neat theory! Could possibly be simulated on a small scale.

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