The puzzling inconsistency between different measurements of the Hubble constant, which describes rate of expansion of the universe, could soon be better understood thanks to a new technique for analysing the explosive merger of two neutron stars.
Conflicting measurements of the Hubble constant arise from two different methods that have been used to measure the parameter. One involves observing stellar explosions called type Ia supernovae and the other involves fitting cosmological models to the cosmic microwave background (CMB) radiation.
The supernova method gives a Hubble constant of 73.5 km/s/Mpc, where a parsec (pc) is 3.26 light-years. This means that a point one million parsecs from Earth is expanding away from Earth at a rate of 73.5 km/s. Meanwhile, analysis of the European Space Agency’s Planck spacecraft’s observations of the CMB suggest a Hubble constant of 67.4 km/s/Mpc. While there are uncertainties in both measurements, the disagreement between the two values is statistically significant.
The conflict suggests that either there is a flaw (or flaws) in how one or both measurements are made and interpreted; or that some sort of new physics is at work. Either way, solving the mystery will reveal new and potentially useful information and physicists ...