Distance & Age: Exploring the Unknown

[foxpoint11]

I thought i understood a light year as a measure of distance.But i keep running into articles that say something like ...around Galaxy NCG 4921 there are a cluster of galaxies estimated to be 13+ billion years old at a distance of 320 light years from earth.How do you get that when you are measuring red shifts?
Or how do you get "there are globular clusters that appear older than the known universe?"
Thank you for any help.

 

[mathman]

http://www.scientificamerican.com/article.cfm?id=how-do-scientists-determi
http://en.wikipedia.org/wiki/Star

Above are a couple of links describing how the ages of stars are determined. The red shift does not have much to do with it.

 

[Chronos]

Redshift limits the maximum age of objects in the universe. That is to say that a galaxy 13 billion years old cannot be at a redshift distance in excess of about 700 million light years. Similarly, a galaxy 6 billion light years distant cannot be more than about 7.7 billion years old. So NGC 4921 at a distance of 260 million light years could be 13.4 billion years old.

 

[foxpoint11]

By George,I think i have it.Thank you mothman and Chronos.

 

[sardar]

I can understand your confusion about the relationship between distance and age in astronomy. Let me explain it in more detail.

A light year is a unit of distance, defined as the distance light travels in one year. It is commonly used in astronomy because it provides a more convenient scale for measuring vast distances in the universe. For example, the distance between the Earth and the Sun is about 8 light minutes, and the nearest star to our Sun is about 4 light years away.

Now, when we observe distant galaxies, we can measure their distance from Earth by using the phenomenon of redshift. This is the stretching of light waves as they travel through expanding space, causing their wavelengths to appear longer, or "shifted" towards the red end of the spectrum. By measuring the amount of this redshift, we can calculate the distance to the galaxy.

However, redshift alone does not tell us the age of the galaxy. To estimate the age, we use other methods such as studying the composition of stars in the galaxy, or measuring the rate of expansion of the universe. These methods can provide an estimate of the age of the galaxy based on its distance from Earth.

As for the statement about globular clusters appearing older than the known universe, this can be explained by the fact that the universe is constantly expanding. This means that the distance to these clusters is increasing over time, making them appear farther away than they actually are. Therefore, their observed age may be older than the age of the universe, which is currently estimated to be around 13.8 billion years.

I hope this helps to clarify the relationship between distance and age in astronomy. It is a complex topic, and scientists are constantly refining our understanding through ongoing research and observations. Thank you for your interest in this fascinating and ever-evolving field of study.