A team from Keio University, led by doctoral student Tatsuya Kotani and professor Tomoharu Oka, has uncovered new insights into the temperature of the cosmic microwave background (CMB) at a redshift of 0.89. They employed the Atacama Large Millimeter/submillimeter Array (ALMA) to measure this temperature, finding it to be 5.13 ± 0.06 kelvin, significantly warmer than the present-day CMB temperature of around 2.7 K.
Understanding the Cosmic Microwave Background
The CMB is essentially the universe’s afterglow from the Big Bang, showing how the universe has cooled over time. By measuring its temperature at various points, scientists can test current cosmological models. While prior research provided temperature estimates from the early universe and the present, data from this intermediate redshift (around when the universe was less than half its current age) were scarce. This new measurement fills a critical gap, supporting theories about cosmic evolution.
Innovative Techniques to Measure Ancient Heat
The team’s approach involved analyzing light from the distant quasar PKS1830–211. This light passed through a background galaxy and interacted with cold hydrogen cyanide (HCN) gas. The gas absorbed certain frequencies of the light, creating absorption lines that served as indicators of temperature for the CMB during that time.
The researchers focused on four HCN rotational transitions. They precisely corrected for uncertainties like the distribution of the gas and how it might have varied over time due to known events. They conducted about 100,000 simulations to refine their findings, ensuring a high level of accuracy.
A Milestone in Cosmology
This measurement confirms the Big Bang model, which predicts that the CMB temperature scales with redshift. Kotani’s findings closely align with theoretical predictions for that redshift, showing a great agreement between observed values and models.
Notably, this is the most accurate measurement of CMB temperature at an intermediate redshift. It improves upon a previous estimate from 2013 by roughly 40%. The new study utilized high-quality ALMA data and a sophisticated uncertainty model, avoiding common pitfalls found in past analyses.
Looking Ahead: Analyzing Cosmic History
While this study centers on a single redshift, its implications go beyond this measurement. It establishes a reliable method for gauging the universe’s past temperature with unprecedented precision. This could pave the way for future studies to explore whether cosmic physical laws have remained constant over time.
Upcoming projects using instruments like the Square Kilometre Array (SKA) will likely expand the horizons of this research, enabling scientists to investigate even earlier epochs of the universe.
In summary, this important measurement at z = 0.89 not only confirms existing theories but also lays the groundwork for deeper exploration into the universe’s evolution, reinforcing the understanding that as space expands, the universe cools consistently.
For more details on this research, you can refer to the article published in The Astrophysical Journal here.
