Astronomers Use a Neutron Star Merger to Measure Cosmic Expansion

• Astronomers used data from a binary neutron star merger to measure the Hubble-Lemaitre Constant, providing a new approach to help resolve the "Hubble Tension."
• The study combined gravitational wave data, Hubble Space Telescope observations, and radio telescope data from the High Sensitivity Array (HSA).
• While the new measurement is less precise than established methods, it aligns more closely with early-Universe values, suggesting current cosmological models may not need fundamental revision.

The Hubble Tension

• Cosmic expansion is measured via the "Cosmic Distance Ladder," which suffers from a discrepancy known as the Hubble Tension:
  • Late-Universe measurements using standard candles (Cepheid Variables, Type Ia supernovae) yield higher expansion rates (~252,000 km/h per Mpc).
  • Early-Universe measurements from the Cosmic Microwave Background (CMB) via the Planck satellite yield lower values (~244,000 km/h per Mpc).

Methodology and Findings

• Researchers, led by the Swinburne University of Technology and CSIRO, analyzed the aftermath of a neutron star collision (kilonova event).
• Observations included jets of particles that glowed for months as they interacted with surrounding gas.
• This independent measurement provides a new data point that challenges theories proposing the Hubble Tension is caused by flaws in our fundamental understanding of cosmology.
• The team plans to examine additional neutron star mergers to refine the accuracy of this method and confirm these initial findings.