Mira Variable Stars

Source: PIB

Context: A new IUCAA-led study (with Nobel laureate Adam Riess as co-author) has used Mira variable stars to measure the Hubble constant with 3.7% precision.

• This provides an independent anchor for the cosmic distance ladder, potentially helping resolve the ongoing Hubble tension.

About Mira variable stars:

• What it is? Mira variables are cool, pulsating red giant stars whose brightness varies regularly due to expansion and contraction cycles in their outer layers.

• Mira variables are cool, pulsating red giant stars whose brightness varies regularly due to expansion and contraction cycles in their outer layers.

• Discovery: The prototype star Mira (Omicron Ceti) was identified as variable in 1596 by David Fabricius and further studied in the 17th century, making it the first recognized variable star.

• The prototype star Mira (Omicron Ceti) was identified as variable in 1596 by David Fabricius and further studied in the 17th century, making it the first recognized variable star.

• Features:

• Brightness variation period: 100–1,000 days. Surface temperature: ~3,000 K (about half of Sun’s surface). Located in late evolutionary stage (dying giant stars). Strong period–luminosity relationship, similar to Cepheid variables. Oxygen-rich types (used in the study) are less affected by metallicity, giving cleaner luminosity calibration.

• Brightness variation period: 100–1,000 days.

• Surface temperature: ~3,000 K (about half of Sun’s surface).

• Located in late evolutionary stage (dying giant stars).

• Strong period–luminosity relationship, similar to Cepheid variables.

• Oxygen-rich types (used in the study) are less affected by metallicity, giving cleaner luminosity calibration.

• Significance:

• Serve as “standard candles” in astronomy—helping measure cosmic distances. Provide a new independent calibration for Type Ia supernovae in the extragalactic distance ladder. Crucial in determining the Hubble constant and addressing the Hubble tension (discrepancy in expansion rate of the Universe measured via early vs. late-Universe methods).

• Serve as “standard candles” in astronomy—helping measure cosmic distances.

• Provide a new independent calibration for Type Ia supernovae in the extragalactic distance ladder.

• Crucial in determining the Hubble constant and addressing the Hubble tension (discrepancy in expansion rate of the Universe measured via early vs. late-Universe methods).