International team tests fundamental constant of the Universe

An international research team, including Carlos Martins, FCT Researcher at the Center for Astrophysics of the University of Porto (CAUP), sought variations in one of the fundamental constants of the Universe—the fine structure constant—whose value is used to characterize the behavior of the electromagnetic force. 

To do this, he used the three most powerful telescopes in the world (VLT, Keck, and Subaru) to search for variations in relative velocity in the light absorption signature of a quasar, an extremely bright nucleus of a distant active galaxy that 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 galaxy absorbed part of the Quasar's spectrum, leaving clues as to how electromagnetic force behaved in each of those eras, 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 consequently in the electromagnetic force, over the last 10 billion years, it has been less than a few parts per million. Michael Murphy, one of the co-authors of the study, believes "this is the most accurate measurement of its kind to date."

 By attempting to unravel the true nature of Dark Energy, presenting new and more accurate 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 "to perform these tests, it is necessary to push current spectrographs to their limits, and improving them is fundamental to modern cosmology."