In a significant breakthrough for cosmology, Indian astronomers have found a novel way to measure the universe’s expansion, helping tackle one of the biggest mysteries in modern astronomy: the Hubble constant.

1. The Cosmic Puzzle: Hubble Constant

The Hubble constant is the rate at which the universe is expanding. Precise measurement of this constant is critical for understanding the age, size, and evolution of the universe. Until now, astronomers primarily relied on Cepheid variable stars and supernovae to gauge cosmic distances. But these methods have left a persistent discrepancy known as the “Hubble tension”, where different measurement techniques yield slightly conflicting values.

2. Mira Variable Stars: A New Cosmic Measuring Stick

The research, led by Prof. Anupam Bhardwaj from the Inter-University Centre for Astronomy and Astrophysics (IUCAA), explored the potential of Mira variable stars — pulsating giant stars — as a new cosmic distance tool.

Monitoring 40 oxygen-rich Miras in 18 stellar clusters within our galaxy, astronomers used data from the Gaia mission to calculate the stars’ absolute luminosities. Unlike Cepheids, Mira luminosity is less affected by metal abundance, making them a highly reliable alternative for cosmic distance measurements.

3. Achieving Precision: 3.7% Accuracy

By using Miras as anchors, the team achieved a Hubble constant measurement with 3.7% precision. This value aligns closely with previous Cepheid-based estimates, suggesting that the longstanding Hubble tension may not be caused by measurement errors, but could point toward new physics in cosmology.

Nobel laureate Adam Riess, a co-author of the study, stated that the results provide a “powerful resolution to the ongoing debate,” hinting at fundamental causes behind the Hubble tension rather than observational mistakes.

4. Why This Discovery Matters

This research not only validates Mira stars as an alternative to Cepheids but also opens a new avenue for studying the universe’s expansion. Mira stars are cooler and easier to observe in certain galaxies, making them an excellent complement to existing cosmic distance ladders.

With upcoming facilities like the Rubin Observatory, astronomers expect to detect thousands of Mira stars across the universe. This will allow for more precise mapping of cosmic distances, helping determine the size and age of the universe with unprecedented accuracy.

5. Future Implications for Cosmology

Dr. Marina Rejkuba, co-author and astronomer at the european Southern Observatory, believes the study will have a long-term impact, establishing Mira variables as a well-calibrated anchor for the Hubble constant.

Beyond refining our understanding of cosmic expansion, this discovery could shed light on dark energy, the early universe, and fundamental physics governing the cosmos.

6. Conclusion

Indian astronomers have now added a powerful new tool to the astronomer’s toolkit. By harnessing Mira variable stars, scientists can achieve more accurate measurements of the universe’s expansion, helping solve one of the most persistent mysteries in modern cosmology. The universe, it seems, is about to reveal its secrets — one pulsating star at a time.