Mira Variable Stars 01 Sep 2025

Mira Variable Stars

• 01 Sep 2025

• 2 min read

• Rapid Fire CA

• Quick Facts For Prelims

• GS Paper - 3

• Space Technology

Source: IE

A new study by the Inter-University Centre for Astronomy and Astrophysics (IUCAA), co-authored by Nobel Laureate Adam Riess, uses oxygen-rich Mira variable stars to measure the Hubble constant with 3.7% precision.

Mira Stars (Omicron Ceti)

• About: Mira is a pulsating red giant star whose brightness varies regularly, with periods ranging from 100 to 1,000 days, due to expansion and contraction cycles in its outer layers. It was the first known variable star (a star that doesn't shine with a constant brightness), identified in the 17th century. They are relatively cool, with surface temperatures around 3,000 Kelvin, and are in the late stages of stellar evolution.

• It was the first known variable star (a star that doesn't shine with a constant brightness), identified in the 17th century.

• They are relatively cool, with surface temperatures around 3,000 Kelvin, and are in the late stages of stellar evolution.

• Significance: They help measure cosmic distances and calibrate the extragalactic distance ladder (a series of methods to determine distances to far-off galaxies). They assist in determining the Hubble constant and resolving the Hubble tension (difference in the Universe’s expansion rate measured from early vs. late-Universe observations) in cosmology.

• They assist in determining the Hubble constant and resolving the Hubble tension (difference in the Universe’s expansion rate measured from early vs. late-Universe observations) in cosmology.

Hubble Constant (H₀)

• Formulated by Edwin Hubble in 1929, it measures the current expansion rate of the universe in kilometers per second per megaparsec (km/s/Mpc), indicating how fast galaxies move apart. H₀ helps estimate the universe’s size and age.

• Edwin Hubble observed that the farther a galaxy is, the faster it moves away. This is measured using redshift, a shift of light toward the red end of the spectrum, indicating the universe is expanding.

Read more: New Method to Determine Hubble Constant

Read more: New Method to Determine Hubble Constant