Why would two close stars have similar metallicity, but different color?

In summary, the question asks why stars in a globular cluster appear one magnitude redder than other nearby stars with similar metallicity, with a color excess of 1 and an extinction of 3.1 in the V band. The difference in metallicity can be explained by one star being older and incorporating less iron during formation. However, the question remains as to why two stars with the same metallicity and from the same part of a galaxy would exhibit significantly different colors. The concept of metallicity may not be relevant in determining this difference, and it may instead be related to the stars' size and temperature. The professor clarified that by "nearby", he meant compared to other stars in the solar system, not within the glob
  • #1
quarky2001
34
0
This is the exact question:

Stars in a globular cluster are observed to be one magnitude redder (in terms of B-V color, so the color excess E_(B-V) = 1, and extinction in the V band is 3.1) than other nearby stars having similar metallicity. What causes this?


I'm aware of why two stars might have different metallicity - one being older than the other means it incorporated less iron from the ISM during formation. I don't understand why two stars with the same metallicity, and from the same part of a galaxy, would have significantly different color.

Does it just relate to their size and temperature? If so, I'm not sure why the question would bother to invoke the concept of metallicity, except to ask that we ignore it.
 
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  • #2
quarky2001 said:
Does it just relate to their size and temperature? If so, I'm not sure why the question would bother to invoke the concept of metallicity, except to ask that we ignore it.
Yes.
 
  • #3
Thanks for the reply - I asked the professor today. He just worded the question funny. By "nearby", he meant that the globular cluster's stars were redder than other stars of similar metallicity "nearby" the solar system, not nearby other stars in the globular cluster!
 

FAQ: Why would two close stars have similar metallicity, but different color?

Why does metallicity affect the color of stars?

The metallicity of a star refers to the abundance of elements heavier than hydrogen and helium in its composition. These elements, such as iron and carbon, affect the way light is absorbed and emitted by the star, which in turn impacts its color. Stars with higher metallicity tend to appear bluer, while those with lower metallicity appear redder.

If two stars have similar metallicity, why do they have different colors?

While metallicity is a major factor in determining a star's color, there are other factors that can also contribute. For example, the age of a star can affect its color, as younger stars tend to be hotter and bluer, while older stars are cooler and redder. Additionally, the size and composition of a star can also play a role in its color.

How can two stars have similar metallicity but different temperatures?

The metallicity of a star is just one aspect of its overall composition. Other factors, such as the amount of hydrogen and helium present, can also impact the star's temperature. For example, a star with a high metallicity but a low amount of hydrogen and helium may have a cooler temperature compared to a star with the same metallicity but higher amounts of these elements.

Can the color of a star change over time due to changes in metallicity?

Yes, the color of a star can change over time as its metallicity changes. This could occur if the star undergoes a process called nucleosynthesis, where elements are created or destroyed within the star. This can alter the star's metallicity and impact its color. Additionally, as a star ages, its metallicity can also change, which can cause its color to shift over time.

How does metallicity impact a star's lifespan?

The metallicity of a star can impact its lifespan in several ways. Stars with higher metallicity tend to have shorter lifespans due to the increased amount of heavy elements in their cores, which can cause them to burn through their fuel at a faster rate. On the other hand, stars with lower metallicity can have longer lifespans as they have less material to burn through. However, other factors such as size and composition can also play a role in a star's lifespan.

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