ESPRESSO spectrograph tests fundamental physics constant

In an attempt to answer the apparently simple and colloquial question "are the laws of physics the same everywhere in the universe, and at all times?"an international team of researchers, which includes the participation of Portuguese researchers from the Institute of Astrophysics and Space Sciences (IAstro), carried out the development of the CosmoESPRESSO project, which aims to investigate whether the alpha constant (α) - the so-called fine structure constant, considered one of the fundamental constants of physics and which corresponds, briefly, to the strength of the electromagnetic interaction between particles - varies in time and space, i.e. whether it is, in fact, constant.

Carlos Martins, from IAstro, says in a statement that "astronomers have made hundreds of measurements of alpha over the last two decades, some of which seemed to say that alpha varied over billions of years, and also with spatial location." On the hypothesis that these variations could be the result of problems in the measuring instruments, the team designed a spectrograph - the ESPRESSO - which, in conjunction with the VLT (Very Large Telescope), constitutes a "perfect machine for measuring the alpha [constant]," in the words of Paolo Molaro, coordinator of the research project. With this equipment, they were able to make measurements of the alpha constant of unprecedented accuracy by observing the light from a quasar - an extremely luminous object detectable from Earth, but very far away.

The results of the research, which are now published as a paper in the journal Astronomy & Astrophysics, show variations of around 1.3 parts per million, significantly smaller than the 10 parts per million of some previous measurements. The team thus demonstrates that the accuracy of the measurements is dependent on how much light can be collected with the measurement instruments used. The higher resolution of the VLT and ESPRESSO allow a closer approximation to the true value of alpha, and the new generations of telescopes and spectrographs, already under development, will lead to even more accurate results.

The ESPRESSO design and construction project involved several European research units. In Portugal, the Instituto de Astrofísica e Ciências do Espaço participated, with funding from FCT. Besides measuring physical constants, the spectrograph is also used, famously, in the search for Earth-like planets located in the habitable zone of distant stars.