Oldest stars in the night sky
The Eternal Wanderers: A Glimpse into Age-old Cosmic Bodies
When we look up into the night sky, we’re not just viewing distant lights. We’re peering deep into history. The stars we see are light years away, meaning the light we see has often taken centuries to reach us. But amongst these celestial bodies, which are the oldest?
Ascending Further Back in Time: Identifying Old Age in Stars
There’s no time-stamp on a star, but scientists use stellar evolution theory and nuclear fusion rates to estimate a star’s age. Stars burn hydrogen in their cores, and as they age, they begin to burn helium, inducing changes in brightness and size that scientists can measure.
There are two primary methods for estimating the age of stars:
- Stellar Evolution Models: These models incorporate the star’s chemical composition, temperature, and brightness to predict its age.
- Nucleocosmochronology: This is the study of isotopic ratios within old stars. This method mainly applies to low-mass stars, which have lifetimes exceeding the age of the universe.
Journeying Through Space-Time: Meet the Methuselah Star
One of the oldest known stars in the universe is HD 140283, commonly known as the Methuselah Star. Estimated to be 14.5 billion years old, this star predates the universe’s calculated age of 13.8 billion years! Astronomers explain this discrepancy by suggesting a small margin of error in their age estimates.
The Ancient Ensemble: Globular Clusters
Globular clusters, spherical collections of stars, are amongst the oldest structures in galaxies. M92, a globular cluster in the constellation Hercules, is particularly old, estimated to be approximately 14 billion years.
A Cosmic Anomaly: The Red Giant, HE 1523-0901
Another fascinating old age wonder is a red giant star, named HE 1523-0901. Estimated to be 13.2 billion years old, this star has been burning for almost as long as the universe has existed!
How Can You Spot These Stalwarts of the Sky?
HD 140283, or the Methuselah Star, can be seen from Earth’s Northern Hemisphere during certain times of the year with a moderate-strength backyard telescope. Unfortunately, the rest require professional grade telescopes, which makes them somewhat elusive to casual stargazers.
Unraveling the Cosmic Curtain
Understanding the age of stars gives us a invaluable glimpse into the universe’s past. And while most of the stars visible to the naked eye are much younger, know that when gazing upward, you’re seeing the light from a collection of ancient cosmic wonders. As the famous astronomer Carl Sagan once put it, we are all star stuff.
Frequently Asked Questions
How do scientists calculate the age of stars?
Scientists use two primary methods: stellar evolution models and nucleocosmochronology—the study of isotopic ratios within old stars.
What is the oldest star we know?
The Methuselah Star, also known as HD 140283, is one of the oldest known stars in the universe at an estimated age of around 14.5 billion years.
Why are some stars older than the estimated age of the universe?
Estimates allow a small margin of error. In addition, our understanding of the universe and its age is always being refined with new discoveries and technologies. This means that over time, the estimated ages of stars and the universe can change.
Article updated at Monday, October 7, 2024