Why in the News?
Recently, scientists from the Inter-University Centre for Astronomy and Astrophysics (IUCAA) made a precise determination of the expansion rate of the universe. They used the cool, giant variable star ‘Mira’ for their calculations.
What is a Mira Variable Star?
Mira is a pulsating red giant star. Its brightness varies regularly. These variations have periods ranging from 100 to 1,000 days. This is due to expansion and contraction cycles in its outer layers.
- It was the first known variable star. A variable star does not shine with a constant brightness. This star was identified in the 17th century.
- They are relatively cool. Their surface temperatures are around 3,000 Kelvin. They are in the late stages of stellar evolution.
1. What is the Significance of the Mira Variable Star?
The Mira Star helps measure cosmic distances. They also calibrate the extragalactic distance ladder. This ladder is a series of methods used to determine distances to far-off galaxies.
The Mira Variable Star assists in determining the Hubble constant. Moreover, they also help resolve the Hubble tension. This tension refers to the difference in the Universe’s expansion rate. This difference is measured from early versus late-Universe observations in cosmology.
2. Facts About the Mira Variable Star
Some interesting facts about the Mira Variable Star are as follows:
- The Mira Star is also known as Omicron Ceti. It is a star that remarkably changes its brightness over time, in a regular pattern.
- The name Mira means “the wonderful” in Latin. It lived up to that name by becoming the prototype for an entire class of stars. These stars are known as Mira variables.
- Astronomers first measured the variability of Mira in the 17th century. It was the first known example of a “variable star.” A variable star does not shine with a constant brightness.
- Mira variables are a type of giant star. They go through regular cycles of expanding and contracting.
- These cycles cause their brightness to vary. This variation is predictable. It typically occurs over periods ranging from 100 to 1,000 days.
- These stars are relatively cool. Their surface temperatures are around 3,000 Kelvin, which is about half the temperature of the Sun’s surface. They are in the late stages of their life.
- One of the most important things about Mira variables is the relationship between their brightness and the duration of their pulsation cycles. Their brightness is strongly connected to how long these cycles last.
- This relationship enables astronomers to utilize them as “standard candles.”
- A standard candle is an object in space. Its actual brightness is known. Scientists can compare how bright the object appears from Earth to its actual brightness. By doing this, they can calculate how far away it is.
- This is a key method used to measure distances in the universe. It forms part of what astronomers call the “extragalactic distance ladder.”
What is the Hubble Constant?
1. The Hubble constant was formulated by Edwin Hubble in 1929. The Hubble constant measures the current expansion rate of the universe. It is expressed in kilometers per second per megaparsec (km/s/Mpc). This measurement indicates how fast galaxies move apart. The Hubble constant helps estimate the size of the universe and its age.
2. Edwin Hubble observed that the farther a galaxy is, the faster it moves away. This observation is measured using redshift. Redshift is a shift of light toward the red end of the spectrum. It indicates that the universe is expanding.
Conclusion
In conclusion, the Mira Variable Star is important for measuring cosmic distances. Moreover, the Mira star also determines the Hubble constant. Thus, knowing the Mira Variable star enhances our understanding of the universe’s expansion.
Frequently Asked Questions
The Mira is a giant red variable.
The Mira Star’s variability is due to the entire star expanding and contracting. This produces a temperature change. It also causes a change in radius. Both of these factors lead to variations in luminosity.
