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Chapter 19: Problem 21

Some galaxies have regions that are relatively blue; other regions appear redder. What does this variation indicate about the differences between these regions?

Short Answer

Expert verified
Blue regions have younger stars and more star formation, while red regions have older stars and less star formation.

Step by step solution

01

- Understanding Star Ages

Blue regions in galaxies indicate areas with younger, hotter stars. In stellar evolution, younger stars tend to be hotter and emit more blue light.
02

- Identifying Old Star Regions

Red regions in galaxies suggest areas with older, cooler stars. Older stars have completed the hotter, blue-emitting phase of their lifecycle and emit more red light.
03

- Relating Color to Star Formation

High rates of star formation occur in the blue regions since new, young stars are forming. On the other hand, red regions have less active star formation, indicating older star populations.
04

- Summary of Color Differences

To summarize, blue regions indicate newer star formation with younger, hotter stars, while red regions indicate older stars and less star formation activity.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

blue regions
In many galaxies, certain areas appear blue to observers. These blue regions are indicators of young stars that are burning brightly. When stars are newly formed, they are very hot and emit light towards the blue end of the spectrum.
This blue light tells us several things:
  • It indicates recent star formation since young stars light up in blue.
  • These regions are often rich in gas and dust, which are the raw materials for new star formation.
Blue regions are exciting for astronomers because they show where new life is beginning in a galaxy. By studying these areas, scientists can learn about the processes that kickstart star formation and how galaxies evolve over time.
red regions
Red regions in galaxies paint a different picture compared to the blue ones. Areas that appear red contain older stars. Over time, stars cool down and their light shifts from blue to red.
Here are some insights from red regions:
  • These regions have stars that are much older.
  • The cooler temperature of these stars means they have lived through the hotter, blue phases of their life cycle.
  • Red regions typically have less gas and dust, suggesting a decline in new star formation.
Studying red regions helps astronomers understand the later stages of stellar evolution. By examining these areas, scientists can gather information about the lifecycle of stars and the history of star formation in various parts of the galaxy.
star ages
The colors of different regions in a galaxy tell us a lot about the ages of the stars within them. Star ages are a crucial part of understanding the life of galaxies.
See how color and star age are related:
  • Younger stars: They are found in blue regions and are typically very bright and hot. These young stars are still in the early stages of their lifecycle.
  • Older stars: They are located in red regions and have cooled down from their initial, hotter stages. These stars are nearing the end of their lifespans.
By mapping out star ages across a galaxy, astronomers can learn about how a galaxy grew and changed over millions or even billions of years.
Understanding star ages also helps us predict the future evolution of galaxies as these stars continue to age and eventually die.

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Most popular questions from this chapter

Describe what astronomers think is happening at the center of a galaxy that contains an AGN.

Suppose the number density of galaxies in the universe is, on average, \(3 \times 10^{-68}\) galaxy \(/ \mathrm{m}^{3} .\) If astronomers could observe all galaxies out to a distance of \(10^{10} \mathrm{pc}\), how many galaxies would they find?

The spectrum of a distant galaxy shows the H \(\alpha\) line of hydro\(\operatorname{gen}\left(\lambda_{\mathrm{rest}}=656.28 \mathrm{nm}\right)\) at a wavelength of \(750 \mathrm{nm} .\) Assume that \(H_{0}=70 \mathrm{km} / \mathrm{s} / \mathrm{Mpc}\). a. What is the redshift \((z)\) of this galaxy? b. What is its recession velocity \(\left(v_{r}\right)\) in kilometers per second? c. What is the distance of the galaxy in megaparsecs?

If you observed a galaxy with an \(\mathrm{H} \alpha\) emission line that had a wavelength of \(756.3 \mathrm{nm}\), what would be the galaxy's redshift? Note that the rest wavelength of the H \(\alpha\) emission line is \(656.3 \mathrm{nm}\). a. 0.01 b. 0.05 c. 0.10 d. 0.15

The Hubble constant is found from the a. slope of the line fit to the data in Hubble's law. b. \(y\) -intercept of the line fit to the data in Hubble's law. c. spread in the data in Hubble's law. d. inverse of the slope of the line fit to the data in Hubble's law.
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