A brand new examine reinforces the Hubble bias, a discrepancy in measurements of the cosmic enlargement charge, offering probably the most correct calibration of Cepheid stars for distance measurements. This discrepancy calls into query basic ideas in physics and has implications for our understanding of darkish power, the time and house continuum, and gravity.
Relating to measuring how briskly the Universe is increasing, the consequence relies on which facet of the Universe you begin from. An EPFL examine has calibrated the perfect secular standards to unprecedented
“data-gt-translate-attributes=”[{” attribute=””>accuracy, shedding new light on the Hubble tension.
The Hubble tension, a discrepancy in the cosmic expansion rate (H0) between early Universe and late Universe measurement methods, has puzzled astrophysicists and cosmologists. A study by the Stellar Standard Candles and Distances research group at EPFLs Institute of Physics has achieved the most accurate calibration of Cepheid stars for distance measurements, amplifying the Hubble tension. The discrepancy calls into question the basic concepts of physics and has implications for the nature of dark energy, the time-space continuum, and gravity.
The Universe is expanding but how fast exactly? The answer appears to depend on whether you estimate the cosmic expansion rate referred to as the Hubbles constant, or H0 based on the echo of the Big Bang (the cosmic microwave background, or CMB) or you measure H0 directly based on todays stars and galaxies. This problem, known as the Hubble tension, has puzzled astrophysicists and cosmologists around the world.
A study carried out by the Stellar Standard Candles and Distances research group, lead by Richard Anderson at EPFLs Institute of Physics, adds a new piece to the puzzle. Their research, published today (April 4) in the journal Astronomy & Astrophysics, achieved the most accurate calibration of Cepheid stars a type of variable star whose luminosity fluctuates over a defined period for distance measurements to date based on data collected by the European Space Agencys (ESAs) Gaia mission. This new calibration further amplifies the Hubble tension.
This Hubble image shows RS Puppis, a type of variable star known as a Cepheid variable. As variable stars go, Cepheids have comparatively long periods RS Puppis, for example, varies in brightness by almost a factor of five every 40 or so days. RS Puppis is unusual; this variable star is shrouded by thick, dark clouds of dust enabling a phenomenon known as a light echo to be shown with stunning clarity. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-Hubble/Europe Collaboration. Acknowledgment: H. Bond (STScI and Penn State University); ESA/Hubble & ESO
The Hubble constant (H0) is named after the astrophysicist who, together with Georges Lematre, discovered the phenomenon in the late 1920s. Its measured in kilometers per second per
The cosmic distance ladder. Credit: NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU)
The new EPFL study is so important because it strengthens the first rung of the distance ladder by improving the calibration of Cepheids as distance tracers. Indeed, the new calibration allows us to measure astronomical distances to within 0.9%, and this lends strong support to the late Universe measurement. Additionally, the results obtained at EPFL, in collaboration with the SH0ES team, helped to refine the H0 measurement, resulting in improved precision and an increased significance of the Hubble tension.
Our study confirms the 73 km/s/Mpc expansion rate, but more importantly, it also provides the most precise, reliable calibrations of Cepheids as tools to measure distances to date, says Anderson. We developed a method that searched for Cepheids belonging to star clusters made up of several hundreds of stars by testing whether stars are moving together through the
The discrepancy has many other implications. It calls into question the very fundamentals, like the exact nature of dark energy, the time-space continuum, and gravity. It means we have to rethink the basic concepts that form the foundation of our overall understanding of physics, says Anderson.
His research groups study makes an important contribution in other areas, too. Because our measurements are so precise, they give us insight into the geometry of the Milky Way, says Mauricio Cruz Reyes, a PhD student in Andersons research group and lead author of the study. The highly accurate calibration we developed will let us better determine the Milky Ways size and shape as a flat-disk galaxy and its distance from other galaxies, for example. Our work also confirmed the reliability of the Gaia data by comparing them with those taken from other telescopes.
Reference: A 0.9% calibration of the Galactic Cepheid luminosity scale based on Gaia DR3 data of open clusters and Cepheids by Mauricio Cruz Reyes and Richard I. Anderson, 4 April 2023, Astronomy and Astrophysics.
DOI: 10.1051/0004-6361/202244775
This project has received funding from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program (grant agreement No 947660).
RIA is funded by the SNSF through an Eccellenza Professorial Fellowship, grant number PCEFP2_194638.
