The Absolute Cosmos: Our universe is getting hotter and hotter as it expands

Scientists already knew that our universe is expanding and the rate of expansion has also been speeding up.

As per scientific theories as the cosmic structures such as galaxy clusters and filaments of universe move apart from each other, universe will observe gradual decline in its mean temperature.

But according to a new study conducted by scientists from Center for Cosmology and AstroParticle Physics (CCAPP) at Ohio State University, shows just opposite of this. As per their findings universe is actually getting warmer as time passes on.

Scientists investigated the thermal history of the universe for the last ten billion years. Investigation revealed that the mean temperature of cosmic gas has increased more than ten times throughout that time and has reached about two million Kelvin today.

The study was led by a research fellow at the CCAP, Yi-Kuan Chiang. The team also has the members from the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The Johns Hopkins University and the Max-Planck-Institute for Astrophysics.

The team examined the thermal data on the LSS (Large Scale Structures) of the universe. LSS refers to the patterns of galaxies and matter on much larger cosmic scales than a single galaxy or groups of galaxies.

These structures are created and shaped by the gravitational collapse of dark matter and gas and can be seen up to billions of light years in length.

In order to measure the thermal changes for the last ten billion years, team used the combined data from the Sloan Digital Sky Survey (SDSS) and ESA’s (European Space Agency) Planck Infrared Astronomical Satellite.

ESA’s Planck was the first mission commissioned by European union to measure the temperature of Cosmic Microwave Background (CMB). SDSS is a major multi spectral imaging and spectroscopic redshift survey and it has created the most detailed 3D maps of the universe.

By using data from Planck and SDSS, scientists compared the temperature of gas clouds farther away from Earth with that of gas clouds closer to Earth.

These measurements helped them to confirm that the mean temperature of gas clouds in the early universe was lower than that of today.

The gas clouds closer to Earth in the universe today has reached the temperatures of about two million Kelvin which is about ten times the mean temperature of the gas clouds around objects lying farther away and back in time.

This is due to the gravitational collapse of the cosmic structure over time and it will more likely keep happening and will intensify as the expansion of the universe continues to accelerate.

Team explained that, the fact that universe is getting hotter is due to natural process of galaxy and structure formation and it has nothing to do with temperature changes on Earth.

Previously, scientists have estimated that universe will keep on cooling as it expands and will eventually result in the Big Freeze.

for more information: The Cosmic Thermal History Probed by Sunyaev-Zeldovich Effect Tomography

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