International team tests fundamental constant of the Universe

An international research team that includes Carlos Martins, FCT Researcher at the Astrophysics Centre of the University of Porto (CAUP), has looked for variations in one of the fundamental constants of the Universe - the fine structure constant - whose value is used to characterize the behaviour of the electromagnetic force. 

To do this, he used the three most powerful telescopes in the world(VLT, Keck and Subaru) to look for relative speed variations in the light absorption signature of a Quasar, an extremely bright nucleus of an active and distant galaxy, which surrounds a supermassive black hole at its center.

 The light from Quasar HS 1549+1919, located 11.5 billion light-years away, passed through three different galaxies, 10, 9 and 8 billion years ago respectively. Each of them absorbed part of the Quasar's spectrum, leaving clues as to how the electromagnetic force behaved at each of those times, which made it possible to measure the fine structure constant α (or Alpha). 

 Previous studies suggested that if there were variations in Alpha, they would be very small. By comparing measurements from the three telescopes, it was possible to minimize measurement errors. The data obtained points to the same answer: if there has been any variation in Alpha, and therefore in the electromagnetic force, over the last 10 billion years, it will have been a variation of less than a few parts per million. Michael Murphy, one of the study 's co-authors, believes that "this is the most precise measurement of its kind to date".

 By trying to unravel the true nature of Dark Energy, presenting new and more precise measurements of the fine structure constant Alpha, this article accepted for publication in the journal Monthly Notices of the Royal Astronomical Society also contributes to the objectives of the project The Dark Side of the Universe, funded by FCT and coordinated by Carlos Martins. The researcher believes that "in order to carry out these tests, it is necessary to push current spectrographs to the limit, and improving them is fundamental for modern cosmology."