SANTA CRUZ DE TENERIFE, 11 Apr. (EUROPE PRESS) –
A new study led by scientists from the Institute of Astrophysics of the Canary Islands (IAC) and the University of La Laguna (ULL) has managed to measure the gravitational redshift in several thousand main sequence stars (where stars spend 90% of their lives ) and giant stars, all of them located in a hundred open clusters.
The study shows the potential of large astronomical observations to test physical laws and verify their universal nature. The results are published in The Astrophysical Journal.
The General Theory of Relativity is one of the fundamental pillars of modern physics. One of the bases that support Einstein’s theory is the so-called Principle of Equivalence. This principle states that light escaping from a region with strong gravity loses energy on its way, making its wavelength redder. This phenomenon is known as gravitational redshift and its measurement is a fundamental test of gravitation.
Although astrophysics provides a wide variety of physical conditions under which redshift should be significant, until very recently observational evidence for this gravitational effect was limited to light emitted by the Sun, white dwarfs, and quasars.
The study led by scientists from the IAC and the ULL is based on the idea of using astrophysical observations to test the validity of physical laws, extending the tests both in space and in cosmic time, and in situations not achievable in a laboratory such as in gravitational fields several tens of times stronger than those existing on Earth.
“The objective of our work has been to measure the effect produced by the gravity of the stars on the light we receive and to verify if the results of these measurements are in agreement with what the theory predicts and, in particular, with the Equivalence Principle “, explains the IAC and ULL researcher Carlos M. Gutiérrez, first author of the article.
The researchers have studied stars that belong to open stellar clusters of the Milky Way and that, therefore, share the same movement, and have measured the differences in the energy of the photons received, depending on the type of star from which they are emitted.
“This effect increases with the mass of the star and decreases with its radius, so that photons emitted by stars similar to the Sun experience an energy loss of the order of two parts in a million, while for stars in the giant phase, with much larger radii, this effect is comparatively much smaller”, highlights Gutiérrez.
To carry out the study, the authors have carried out extensive sampling, based on a catalog of 7 million stars provided by ESA’s Gaia mission, and have selected nearly 100 open clusters and 8,000 stars distributed throughout the galaxy. .
For the IAC and ULL researcher Nataliya Ramos Chernenko, co-author of the article, “this study represents an important advance, since there were hardly any previous studies on ‘normal’ stars apart from the Sun”. “It is also one of the first studies based on non-degenerate stars, that is, stars that are not in the final stages of their existence, including dwarf and giant stars, and in open clusters,” she adds.
In addition to obtaining one of the most extensive validations of a fundamental physical concept, the study has also confirmed that estimates of the mass and radius of stars based on theoretical models are correct. “Testing predictions of General Relativity helps to rule out other theories of gravity that have been proposed as alternatives to explain the dominance of dark matter and energy in the Universe, as well as to validate navigation and positioning systems, such as GPS, that do not would work if Einstein’s theory were not taken into account”, concludes Gutiérrez.
