The universe is getting hot, hot, hot, a new study suggests
Temperature has increased about 10 times over the last 10 billion years


Date:
November 10, 2020
Source:
Ohio State University
Summary:
The universe is getting hotter, a new study has found. The study
probed the thermal history of the universe over the last 10 billion
years. It found that the mean temperature of gas across the universe
has increased more than 10 times over that time period and reached
about 2 million degrees Kelvin today -- approximately 4 million
degrees Fahrenheit.



FULL STORY ==========================================================================
The universe is getting hotter, a new study has found.


==========================================================================
The study, published Oct. 13 in the Astrophysical Journal, probed the
thermal history of the universe over the last 10 billion years. It found
that the mean temperature of gas across the universe has increased more
than 10 times over that time period and reached about 2 million degrees
Kelvin today - - approximately 4 million degrees Fahrenheit.

"Our new measurement provides a direct confirmation of the seminal work
by Jim Peebles -- the 2019 Nobel Laureate in Physics -- who laid out
the theory of how the large-scale structure forms in the universe,"
said Yi-Kuan Chiang, lead author of the study and a research fellow at
The Ohio State University Center for Cosmology and AstroParticle Physics.

The large-scale structure of the universe refers to the global patterns
of galaxies and galaxy clusters on scales beyond individual galaxies. It
is formed by the gravitational collapse of dark matter and gas.

"As the universe evolves, gravity pulls dark matter and gas in space
together into galaxies and clusters of galaxies," Chiang said. "The
drag is violent - - so violent that more and more gas is shocked and
heated up." The findings, Chiang said, showed scientists how to clock
the progress of cosmic structure formation by "checking the temperature"
of the universe.



==========================================================================
The researchers used a new method that allowed them to estimate the
temperature of gas farther away from Earth -- which means further back in
time -- and compare them to gases closer to Earth and near the present
time. Now, he said, researchers have confirmed that the universe is
getting hotter over time due to the gravitational collapse of cosmic
structure, and the heating will likely continue.

To understand how the temperature of the universe has changed over time, researchers used data on light throughout space collected by two missions, Planck and the Sloan Digital Sky Survey. Planck is the European Space
Agency mission that operates with heavy involvement from NASA; Sloan
collects detailed images and light spectra from the universe.

They combined data from the two missions and evaluated the distances
of the hot gases near and far via measuring redshift, a notion that astrophysicists use to estimate the cosmic age at which distant objects
are observed. ("Redshift" gets its name from the way wavelengths of
light lengthen. The farther away something is in the universe, the
longer its wavelength of light. Scientists who study the cosmos call
that lengthening the redshift effect.) The concept of redshift works
because the light we see from objects farther away from Earth is older
than the light we see from objects closer to Earth - - the light from
distant objects has traveled a longer journey to reach us.

That fact, together with a method to estimate temperature from light,
allowed the researchers to measure the mean temperature of gases in
the early universe -- gases that surround objects farther away -- and
compare that mean with the mean temperature of gases closer to Earth --
gases today.

Those gases in the universe today, the researchers found, reach
temperatures of about 2 million degrees Kelvin -- approximately 4 million degrees Fahrenheit, around objects closer to Earth. That is about 10
times the temperature of the gases around objects farther away and
further back in time.

The universe, Chiang said, is warming because of the natural process
of galaxy and structure formation. It is unrelated to the warming
on Earth. "These phenomena are happening on very different scales,"
he said. "They are not at all connected." This study was completed in collaborations with researchers at the Kavli Institute for the Physics
and Mathematics of the Universe, Johns Hopkins University, and the Max
Planck Institute for Astrophysics.


========================================================================== Story Source: Materials provided by Ohio_State_University. Original
written by Laura Arenschield. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Yi-Kuan Chiang, Ryu Makiya, Brice Me'nard, Eiichiro Komatsu. The
Cosmic
Thermal History Probed by Sunyaev-Zeldovich Effect
Tomography. The Astrophysical Journal, 2020; 902 (1): 56 DOI:
10.3847/1538-4357/abb403 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/11/201110133132.htm

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