IUCAA-led study uses Mira variable stars to measure the Hubble constant with 3.7% precision
A study led by Prof. Anupam Bhardwaj of IUCAA, Pune, with Nobel laureate Adam Riess as co-author, used 40 oxygen-rich Mira variable stars to measure the Hubble constant with 3.7% precision.
Summary
A study led by Professor Anupam Bhardwaj of the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, used 40 oxygen-rich Mira variable stars in 18 star clusters of our galaxy to calibrate the cosmic distance ladder, the Ministry of Education said on 31 August 2025. Distances from the European Space Agency's Gaia mission gave an absolute period-luminosity relation for the Miras, providing a calibration of supernovae without using Cepheid variables and a Hubble constant with 3.7% precision. The work, published in the Astrophysical Journal, found metal abundance affects Mira luminosity three times less than Cepheids, and co-author Nobel laureate Adam Riess said the agreement with Cepheid-based values suggests the Hubble tension is unlikely to be due to measurement errors.
Key facts
- Lead author
- Prof. Anupam Bhardwaj, IUCAA Pune
- Co-author
- Nobel laureate Adam Riess
- Sample
- 40 oxygen-rich Mira variables in 18 Milky Way clusters
- Distances from
- ESA's Gaia mission (13,000–55,000 light-years)
- Result
- Hubble constant with 3.7% precision, independent of Cepheids
- Journal
- Astrophysical Journal
- Finding
- Metallicity affects Mira luminosity ~3× less than Cepheids
Practice MCQs 3 questions
The IUCAA-led study publicised on 31 August 2025 used which type of stars to measure the Hubble constant independently of Cepheids?
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Correct answer: D — Oxygen-rich Mira variable stars
The study used 40 oxygen-rich Mira variable stars in 18 clusters of our galaxy as anchors.
Precise geometric distances to the star clusters in the IUCAA Mira study were provided by:
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Correct answer: C — ESA's Gaia mission
The release says the European Space Agency's Gaia mission provided precise geometric distances to the clusters (13,000–55,000 light-years away).
Consider the following statements about the IUCAA Mira-variable study (August 2025): 1. It determined the Hubble constant with 3.7% precision. 2. It found that metal abundance affects Mira luminosity about three times more than it affects Cepheids. Which of the above is/are correct?
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Correct answer: A — 1 only
Statement 1 is correct. Statement 2 is wrong: metal abundance affects Mira luminosity three times LESS than Cepheids, which makes Miras a promising alternative.