Fundamental constant found constant 1.5 billion years after the Big Bang
FOM PhD student Julija Bagdonaite and FOM workgroup leader Wim Ubachs (VU University) have confirmed that the mass ratio between electrons and protons has remained the same over the past 12.4 billion years. They came to this conclusion after observing hydrogen molecules in a distant galaxy.
The researchers observed an absorption spectrum of hydrogen molecules in a distant galaxy in the line-of-sight to the quasar system J1443+272 with the ESO Very Large Telescope at Paranal, Chile. The analysis of the observations shows that the absorbing galaxy is at a cosmological redshift of z=4.22, which means that the absorptions have taken place some 12.4 billion years ago when the universe had only ten percent of its age today.
Detailed analysis of the spectrum, performed in collaboration with scientists from Swinburne University of Technology at Melbourne (Australia), reveals further that the proton-electron mass ratio, a fundamental and dimensionless constant of nature that is key to the spectrum of molecules, has not changed during that long time interval. In quantitative terms: it has remained constant within a limit of 0.001 percent.
Full range
The VU team has by now observed and analysed some eight systems of molecular hydrogen at redshifts in the range 2-4.2, covering look back times from 10 to 12.4 billion years, with optical telescopes. In addition the methanol molecule, another sensitive probe for varying constants, was observed at redshift z=0.89 by means of radio astronomy. These observations cover the full range of the phase transition in our universe, that from a fully matter-dominated (early) universe to a universe that is built mainly from dark energy (72 percent at present).
Dark energy
Theories predict, that under the assumption that dark energy corresponds to a dynamical field (instead of a non-active cosmological constant), this field should effectively lead to varying coupling strengths. This has not been observed so far, meaning that the observations are not sufficiently sensitive, or that dark energy would not correspond to dynamical scalar fields.
The report on these findings is published on 19 February 2015 in Physical Review Letters with a 'Editors suggestion' label.
For more information on varying constants and astronomical observations of highly redshifted molecular hydrogen, see Ubach's website.