New ‘cosmic scale’ measurement leaves us with a major physics problem: ScienceAlert
Some mysteries in science disappear with more precise measurements, solving gaps with a whiff of new data. And sometimes a second look just reinforces that you have a mystery on your hands.
It’s the latter in the case of a new study that challenges the most fundamental physical laws of the Universe.
THE Hubble constant is an expression of the expansion rate of the Universe. Unfortunately, there is more than one solution for this, depending on how it is measured.
A rate of expansion calculated using the faint glow left by the first light to exist, known as the cosmic microwave backgroundis about 68 kilometers per second/megaparsec. Looking at how stars and galaxies are moving away from us today, it’s more like 73 km/sec/Mpc.
These two sets of measurements clearly do not match. Not even close. But if we get a small detail wrong, like the actual distance of distant objects when we calculate their flight in the distance, it’s possible that the two numbers could come close to overlapping.
In this latest study, researchers at the Ecole polytechnique fédérale de Lausanne (EPFL) used data from the Gaia spacecraft to recalibrate the brightness of pulsating stars known as Cepheids.
By relating known luminosity to distance, and then looking for examples in the depths of space, we can precisely cobble together a scale for the cosmos. This calibration is the first rung of a “cosmic scale” used to calculate ever greater distances in space, and through this, the rate at which the Universe is expanding.
The good news is that improved accuracy helps us better understand the Hubble constant.
Then there is the not so good news. The latest data confirms a Hubble constant or expansion rate of 73.0 ± 1.0 km/s/Mpc, making it no closer to the alternative measure of 67.4±0.5km/s/Mpc.
This gap (the “Hubble tension”) of 5.6 km/s/Mpc remains a significant problem – something is wrong somewhere, and now we are even more certain of it than ever.
“The more confirmation we get that our calculations are correct, the more we can conclude that the discrepancy means our understanding of the Universe is in error, that the Universe is not quite as we thought,” said EPFL astrophysicist Richard Anderson.
The way the new readings were taken, through the discovery of new Cepheid clusters and observations from multiple angles, as well as cross-references to other clusters, can be used in many other light and light calculations. distance in space, according to the researchers.
In fact, it will even be useful in determining the geometry of the Milky Way as a whole: how the elements of our galaxy are positioned and how this relates to other galaxies further away from our home planet.
“The very precise calibration we have developed will allow us to better determine the size and shape of the Milky Way as a flat-disc galaxy and its distance from other galaxies, for example,” said astrophysicist Mauricio Cruz Reyes, from EPFL.
“Our work also confirmed the reliability of Gaia’s data by comparing it to that taken by other telescopes.”
The research has been published in Astronomy & Astrophysics.
