The universe is getting hotter as it gets older — here’s why
Surfing the cosmic web
Thecosmic web(sometimes called the cosmic net) began as material connected to the first galaxies in the known Universe. As clumping began, their gravitational influence became more pronounced, bringing in still more gas.
“As the Universe evolves, gravity pulls dark matter and gas in space together into galaxies and clusters of galaxies. The drag is violent — so violent that more and more gas is shocked and heated up,” said Yi-Kuan Chiang, research fellow at the Ohio State University Center for Cosmology and AstroParticle Physics.
By measuring the temperatures of these intergalactic ribbons, it is possible to determine the temperature of theUniverseduring different eras. This is accomplished through a process known as the Sunyaev-Zeldovich effect.
The “echo” of the Big Bang can be seen today as the cosmic microwave background radiation. Billions of years ago, as thiselectromagnetic radiationencountered hot electrons in the ribbons it gathered energy, and the gas became visible. The degree to which this effect occurs is dependent on the thermal pressure, which in turn is determined by the temperature of the electrons.
By determining the degree of the Sunyaev-Zeldovich effect, it is possible to determine the thermal pressure within the gas, from which astrophysicists determine the temperature of the electrons.
Walking the Planck
Details of the cosmic microwave background were provided by the ESA’s Planck satellite. Observations ofgalaxiescame from the Sloan Digital Sky Survey (SDSS). By combining data from both sky surveys, astronomers were able to piece together details of this intergalactic heating.
“To do so, we cross-correlate eight sky intensity maps in the Planck and Infrared Astronomical Satellite missions with two million spectroscopic redshift references in the Sloan Digital Sky Surveys,” researchers detail inThe Astrophysical Journal.
The team found the mean electron temperature within these ribbons rose from 700,000 Kelvin eight billion years ago to roughly two million Kelvin today.
This heating was also found to be the result of gas flowing into theribbons, as it is shock heated in the collapsing structures.
“For 20 years, we have been studying how to measure this using the Sunyaev-Zeldovich effect. We now have finally measured the temperature of the Universe, not only thanks to the remarkable progress in observational data, but also due to the dedicated efforts of brilliant young scientists such as Yi-Kuan Chiang and Ryu Makiya. This is very satisfying,”Eiichiro Komatsu, director at the Max Planck Institute for Astrophysics, stated.
As time goes on, theribbons of the cosmic webare starting to be the hot place to hang out!
This article was originally published onThe Cosmic CompanionbyJames Maynard, founder and publisher of The Cosmic Companion. He is a New England native turned desert rat in Tucson, where he lives with his lovely wife, Nicole, and Max the Cat. You can read this original piecehere.
Astronomy News with The Cosmic Companionis also available as a weekly podcast, carried on all major podcast providers. Tune in every Tuesday for updates on the latest astronomy news, and interviews with astronomers and other researchers working to uncover the nature of the Universe.
Story byThe Cosmic Companion
Exploring the wonders of the Cosmos, one mystery at a time.Exploring the wonders of the Cosmos, one mystery at a time.
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