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Chapter 23: Problem 37

Using the current model of galaxy formation, describe how galaxies should appear as you look further back in time. Are the features you described observed?

Short Answer

Expert verified
Galaxies further back in time appear smaller, irregular, and show high star formation and merger activity. Observations support these features.

Step by step solution

01

- Understand the current model of galaxy formation

The current model of galaxy formation suggests that galaxies grow and evolve over time through a combination of dark matter accumulation, gas accretion, and mergers. Early in the universe, galaxies formed from small fluctuations in the density of matter.
02

- Define the appearance of galaxies as you look further back in time

As you look further back in time, galaxies should appear younger and less evolved. They would be smaller, more irregularly shaped, and show signs of ongoing formation, such as high rates of star formation and frequent galaxy mergers.
03

- Correlate observational evidence with theoretical predictions

Observations using powerful telescopes, such as the Hubble Space Telescope, confirm these theoretical predictions. Distant galaxies observed in the early universe are indeed smaller, less structured, and show signs of intense star-forming activity and mergers.

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Key Concepts

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

Dark Matter
Dark matter plays a crucial role in galaxy formation. Unlike ordinary matter, dark matter doesn't emit, absorb, or reflect light, making it invisible. However, its presence is inferred from its gravitational effects on visible matter. Early in the universe, small fluctuations in the density of dark matter created potential wells. These wells attracted gas, forming the seeds of galaxies. Over time, dark matter continued to pull in more mass, shaping the structure and evolution of galaxies. Without dark matter, galaxies would not have enough gravitational pull to hold themselves together.
Gas Accretion
Gas accretion is a fundamental process for galaxy growth. In the early universe, intergalactic gas was pulled into the potential wells created by dark matter. This gas gradually cooled and condensed, forming stars and star clusters within galaxies. Gas accretion continues to fuel star formation, replenishing the gas supply as it's consumed by forming stars. Observations show that even today, galaxies continue to accrete gas from their surroundings, an ongoing process essential for sustaining star formation and galaxy evolution.
Galaxy Mergers
Galaxy mergers are another key mechanism in galaxy formation and evolution. Smaller galaxies frequently collide and merge to form larger galaxies. These interactions can trigger bursts of star formation and significantly alter the structure and dynamics of the resultant galaxy. Mergers are more common in the early universe, contributing to the irregular and chaotic appearance of young galaxies. As galaxies merge, they grow in size and mass, eventually evolving into the more stable and structured galaxies we observe in the present universe. This process is still observable today in galaxy clusters where mergers continue to happen.
Star Formation
Star formation is the process by which dense regions of molecular clouds in galaxies collapse to form stars. Early galaxies had high rates of star formation due to abundant cold gas and frequent mergers. Star formation lights up galaxies, making them visible across the universe. The rate of star formation has declined over time as gas supplies are depleted and galaxies evolve into more stable configurations. Studying distant galaxies shows that young, less evolved galaxies have higher rates of star formation, supporting the theoretical models of galaxy formation. Observations with telescopes confirm that young galaxies are bright with ongoing star-forming activity.

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Most popular questions from this chapter

Place the following in order of occurrence. a. Degenerate Era b. Primordial Era c. Black Hole Era d. Stelliferous Era e. the Big Bang

Neutrinos are an example of a. hot dark matter. b. cold dark matter. c. charged particles. d. both a and c

Gravitational lenses can be used to find a. planets in the interstellar medium. b. the presence of dark matter around galaxies. c. the masses of galaxy clusters. d. all of the above

What are some of the observational signs that dark matter exists?

Imagine that there are galaxies in the universe composed mostly of dark matter, with relatively few stars or other luminous normal matter. If this were true, how might you learn of the existence of such galaxies?
See all solutions

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