A reasearch with the participation of astronomers from the DAS showed that the universe has cooled to the temperature predicted by the Big-Bang hypothesis.

A milestone in the Big-Bang theory was the prediction made in 1948 by Gamow, Alpher and Herman about the residue of the initial cosmic radiation: the so-called Cosmic Microwave Background Radiation (CMBR, later discovered by Penzias and Wilson in 1965). Thus, according to the standard model of Big Bang the universe is expanding lowering the temperature of this radiation.

A study by an international team of astronomers including participation of researchers Pasquier Noterdaeme and Sebastián López of the Department of Astronomy (DAS) at the University of Chile, allowed precise measurements of the temperature of the universe over billions of years. These measurements agree well with the standard model of Big Bang.

But how do you measure the temperature of the Universe? The scientists studied the rotational levels of carbon monoxide (CO) molecules, detected in the interstellar medium of distant galaxies with the Very Large Telescope (VLT) located at Cerro Paranal. The measurements confirm that the temperature of the universe has been declining over time, and match very well with the predictions of the Big-Bang theory, providing a strong constraint to alternative models for the evolution of the universe.

The results were submitted to the Astronomy and Astrophysics journal: "The evolution of the cosmic microwave background temperature. Measurements of TCMB at high redshift excitation from carbon monoxide. " (Noterdaeme et al. 2011, A&A, 526, L7)

Figure caption

Black body temperature of the cosmic background radiation (in degree Kelvin) vs. time (in billions of years). Star represents the local measure (t = 0, COBE, Mathers et al. 1999). Measures based on the rotational excitation of CO are represented by the red dots between 9 and 12 billion years in the past. Other measures are based on (i) the Sunyaev-Zel'dovich (blue triangles, Luzzi et al. 2009) and (ii) the analysis of atomic carbon fine structure (green squares, Cui et al. 2005, Ge et al. 1997, Srianand et al. 2000, Molaro et al. 2002). Upper limits from analysis of atomic carbon (Srianand et al. 2008) and analysis of molecular absorption (black circle, Wiklind & Combes 1996). The curve represents the theoretical relationship of the standard model of Big Bang.