Universe 7 Billion Years Ago cooled as Predicted, Landmark Study Confirms
Tokyo, Japan - In a breakthrough for cosmology, an international team of researchers has directly measured the temperature of the universe when it was approximately 7 billion years old, confirming predictions made by the standard model of cosmology. Utilizing the Atacama Large Millimeter/submillimeter Array (ALMA), the team observed the absorption of cosmic microwave background (CMB) radiation by hydrogen cyanide (HCN) gas, yielding a temperature of 10.2 Kelvin (-262.95°C or -443.31°F) at a redshift of 0.89. The findings, released by Keio university, provide a crucial benchmark for understanding the universe’s thermal history and testing the fundamental laws of physics across cosmic time.
This precise measurement represents the most distant direct temperature reading of the universe to date, offering a vital test of the assumption that the universe cools predictably as it expands. By analyzing the absorption spectra of HCN, researchers were able to determine both the optical depth and excitation temperature of the gas, ultimately revealing the CMB temperature at that specific point in cosmic history. The study demonstrates a reliable method for probing the early universe’s temperature, opening new avenues for investigating potential variations in physical constants over time.
The research team’s success hinges on observing quasars – extremely luminous active galactic nuclei - at high redshifts. As the CMB photons travel across vast cosmic distances, they interact with intervening gas clouds, leaving subtle absorption signatures in the quasar’s spectrum. Analyzing these signatures allows scientists to infer the temperature of the CMB at the time of interaction. The Keio University press release highlights that future observations targeting quasars at even higher redshifts, utilizing instruments like the Square Kilometre Array (SKA) and the next-generation Very Large Array (ngVLA), promise to extend this method further, improving sensitivity and expanding the range of measurable redshifts.
This measurement at redshift 0.89 serves as a critical validation of the cosmological principle – the idea that the universe is homogeneous and isotropic on large scales – and reinforces the understanding that the universe’s cooling behavior aligns with theoretical predictions. The team’s work provides a solid foundation for future investigations into the evolution of the cosmos and the potential for uncovering new physics beyond the standard model.
