Astronomers at Ohio State University have analyzed the evolution of the universe's average gas temperature over the past 10 billion years. Their research reveals a dramatic rise, with modern gas now approaching two million degrees Celsius.
Observing distant cosmic objects is like peering into the past. Light from an object 10 billion light-years away shows us that object as it existed when the universe was young.
In this study, the Ohio State team measured gas temperatures spanning about 10 billion years of cosmic history.
Using data from the Planck mission and the Sloan Digital Sky Survey (SDSS), researchers identified gas pockets and analyzed their light's redshift. Redshift occurs as light stretches during the universe's expansion, helping determine distances.
They focused on gas from 10 billion years ago, progressing to younger structures, and estimated temperatures from the light signatures. Results show today's "modern" gas averages close to two million degrees Celsius—about 10 times hotter than gas from 10 billion years ago.
This warming aligns with expectations: as gas collapsed into galaxies and clusters, gravitational energy heated it. The trend will likely continue.
Importantly, this measures gas near cosmic structures, not the universe overall. The cosmic microwave background sets the average universe temperature at around -270.4°C, just above absolute zero.
Details are published in The Astrophysical Journal.
