How does the color of a star indicates its age?

Question

How does the color of a star indicates its age?

Answer 1

blue as the youngest as red as the oldest...

it also indicates the temperature, blue as the hottest, to yellow  then orange, then finally red as the not so hottest but still will melt you from miles away :)

oh our sun is also a star do you know that? that's y there's this issue that when our sun gets so red, it might explode, then it will create a black hole...i don't hear that anymore but it's true as i have heard of it...

Answer 2

Summary

The student will find the ages of two clusters by plotting stellar data on a color-magnitude diagram.

Background and Theory

In class we have touched on many characteristics of stars: their distance, intrinsic luminosity, surface temperature, composition, mass and radius. However, this tells us very little about their actual histories. In order to study the life cycle of stars, we would like to know the age of the stars we observe. Star clusters give us an opportunity to determine the age of their member stars, because we can assume that all the stars were born at roughly the same time.

Normally, a Hertzsprung-Russell (H-R) diagram plots the spectral type of a star (or its temperature, which is equivalent) against the star's intrinsic luminosity (or absolute magnitude). However, in this lab we are going to construct a slightly different kind of H-R diagram, one which features the color of stars.

This isn't as easy as it sounds. Think, for example, of how hard it is to get two people to agree on the exact color of a sweater. Now imagine if we had to get all astronomers to agree on the color of every object in the sky! To avoid this situation, astronomers measure the brightness of a star through filters. A filter only lets light of specific wavelengths through. For example, if you were to look through a red filter, everything would appear different shades of red, because only red wavelengths of light can pass through the filter and into your eye.

Astronomers like to compare the brightness of a star (or anything, really) in one filter to its brightness in a different one. Since stars are blackbodies they will appear brighter in one filter than in another, and the difference between these brightnesses is a number which we use to describe the stars' color. Using this technique allows us to give color a universal meaning.

Since color and temperature and spectral type are all equivalent, we can plot the color of a star against its brightness (measured in magnitudes) as a way of building an H-R diagram without taking the star's spectrum. This type of H-R diagram is called a "color-magnitude" diagram. This method is particularly useful with star clusters where taking the spectrum of thousands of closely-spaced stars would be impossible.

Today we will be looking at actual data for two star clusters: an open cluster called M45 and a globular cluster called 47 Tuc. Each cluster contains thousands of stars, but we have only plotted the data for a representative few. The table below provides the data.

The filter combination we will use is B-V: the difference between the star's brightness in a blue filter and in a yellow filter. The important thing to know is that the bigger B-V is the redder the star is -- and the smaller it is, the bluer the star

Main Sequence Lifetimes  Spectral   Type Color

B-V  Lifetime  (years) Mass

(solar masses)

O  -0.4  < 106  40 Mo

B  -0.2  3 X 107  10 Mo

A  0.2  4 X 108  2.3 Mo

F  0.5  4 X 109  1.4 Mo

G  0.7  1 X 1010  1.0 Mo

K  1.0  6 X 1010  0.7 Mo

M  1.6  >1011  0.3 Mo



Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

other resources are :

Stars are balls of (mostly) Hydrogen gas that are so hot that they glow. The heat from normal stars comes from a fusion reaction in their cores, in which they take 4 Hydrogen nuclei and make one Helium nucleus. The rate at which this fusion reaction takes place depends on the temperature - the hotter the star's core, the faster the reactions take place.

Not all stars are created equal. Stars are formed when a large gas cloud collapses. When the gas is divided up among the protostars, most of the clumps of gas are toward the lower end of possible stellar masses, and only a few are toward the higher end. Some stars are created with masses up to 50 times the mass of the sun, and some are formed with as low as 8% of the mass of the sun. When a cloud of gas collapses to form stars, many more low-mass stars are formed than high-mass stars.

Massive stars have very hot cores. Since the rate of fusion depends goes up with temperature, fusion reactions happen much more quickly in the cores of high-mass stars than in those of low-mass stars. Even though high-mass stars have more fuel (they have more Hydrogen than low-mass stars), they use it up very quickly, and live only a small fraction of the time that a low-mass star can live. For example, a blue star lives only a few million or tens of millions of years, while a red star can live for tens or hundreds of billions of years.

When a group of stars is formed, there are a few high mass stars, more medium mass stars, and many low-mass stars. The high-mass stars are very bright, and their color (blue) dominates the color of the group (it appears blue). As time goes by, the high mass stars use up their fuel and die, leaving medium- and low-mass stars. Even though there are more medium mass than low mass stars, the medium mass stars are brighter, so they contribute most of the light of the group and the group will appear yellow. After more time passes, even these medium mass stars die, leaving behind only cool, red stars, and the group appears red. So the color of a group of stars is an indication of its age - if it's blue, there are hot stars (which don't live very long), so the group must not be very old. If it's red, there are only cool stars, so it must be very old.

Answer 3

It doesn't. The color of a star indicates its temperature.

Answer 4

Well it mostly doesnt, it indicates its tempature. But stars that are older and about to explode seem brighter in the sky.

For tom ryan: the sun wont explode for another estimated 10 billion years so its nothing we have to worry about right now

Answer 5

As has already been said - color is more of an indication of temperature than age.

Luminosty helps in conjunction with color - but even that isn;t definitive.

protostars tend to the bright and red.

But middle aged stars can be any color - however blue stars will be bright and red stars will be dim.

Once they get older they will be red and bright.

But then stars like the sun become white dwarfs, which start out blue-white and dim, and cool thru yellow, orange, red etc and get progressively dimmer.

You cannot determine the age of a star simply from its color.

Answer 6

Older stars are red than young stars are blue.

Explanation:

Basically, the color of light that a star emits is somewhat related to its age, whereas the color of light that we actually observe from a star is related to the speed at which it's moving with respect to us.

Stars emit colors of many different wavelengths, but the wavelength of light where a star's emission is concentrated is related to the star's temperature - the hotter the star, the more blue it is; the cooler the star, the more red it is.

There are a couple of ways in which this relates to a star's age: For most of a star's life, it is on the "main sequence", which means that it is undergoing nuclear burning of hydrogen in its center and the energy produced from that process balances it against the force of gravity. The high-mass stars are very bright, and their color (blue) dominates the color of the group (it appears blue). When it runs out of hydrogen to burn, the star becomes unbalanced, and its size and temperature can change. For some stars, particularly those that start off very hot, the temperature at this point in the star's life will tend to decrease and therefore the star will become red. So that is one way in which older stars are redder than young stars which are bluer.

Answer 7

it doesnt.. the color indicates the temperature