Recently, the most precise determination of the expansion rate of the universe was made using cool, giant variable stars ‘Mira’ by the scientists from Inter-University Centre for Astronomy and Astrophysics (IUCAA).
About Mira Stars:
Mira, also known as Omicron Ceti, is a star that remarkably changes its brightness over time, in a regular pattern.
The name, Mira, means "the wonderful" in Latin, and it lived up to that name by becoming the prototype for an entire class of stars known as Mira variables.
With the variability first measured by astronomers in the 17th century, Mira was the first known example of a "variable star"—a star that doesn't shine with a constant brightness.
Mira variables are a type of giant star that go through regular cycles of expanding and contracting.
These cycles cause their brightness to vary in a predictable way, typically over periods ranging from 100 to 1,000 days.
These stars are relatively cool, with surface temperatures around 3,000 Kelvin (about half the temperature of the Sun’s surface), and they are in the late stages of their life.
One of the most important things about Mira variables is that there is a strong relationship between how bright they are and how long their pulsation cycles last.
This relationship allows astronomers to use them as "standard candles."
A standard candle is an object in space whose true brightness is known. By comparing how bright the object appears from Earth to how bright it actually is, scientists can calculate how far away it is.
This is a key method used to measure distances in the universe, forming part of what astronomers call the "extragalactic distance ladder."
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