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Chapter 20: Problem 29

Describe the characteristics of irregular galaxies.

Short Answer

Expert verified
Irregular galaxies lack a distinct shape, contain gas and dust enabling star formation, and may form through collisions.

Step by step solution

01

- Definition

Irregular galaxies lack a distinct, regular shape. Unlike spiral or elliptical galaxies, they do not have a defined structure.
02

- Composition

Irregular galaxies often contain large amounts of gas and dust, which enables active star formation. They have many young, blue stars along with older stars.
03

- Formation

Irregular galaxies may form from collisions or interactions with other galaxies, which can distort their shape. They could also be remnants of larger galaxies torn apart by gravitational forces.
04

- Examples

The Magellanic Clouds, which are satellite galaxies of the Milky Way, are examples of irregular galaxies.

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Key Concepts

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

Galactic Structures
Irregular galaxies are fascinating because they break the mold of traditional galactic shapes. Unlike spiral galaxies, which have well-defined arms, or elliptical galaxies, which have smooth, featureless shapes, irregular galaxies do not follow a set structure. They look chaotic and disorganized. This lack of a clear shape is what makes irregular galaxies unique. Despite their apparent randomness, they still contain a mixture of gas, dust, and stars. This internal variety can make them interesting subjects of study for understanding the diversity of galactic forms.
Star Formation
Irregular galaxies are hotspots for star formation. Due to their abundant gas and dust, irregular galaxies can rapidly form new stars. Unlike more settled galaxies, such as ellipticals, which mainly consist of older stars, irregular galaxies often have a higher proportion of young, blue stars. These youthful stars are formed from the raw material present in the galaxy's chaotic environment. The continuous cycle of star formation and death in irregular galaxies keeps them vibrant and full of energy. This contrasts with galaxies that have exhausted their star-forming material and contain mostly aged stars.
Galactic Collisions
Irregular galaxies frequently owe their shapelessness to past interactions or collisions with other galaxies. When galaxies collide, the gravitational forces involved can drastically distort their shapes, leading to a chaotic and irregular appearance. This process can trigger bursts of star formation as gas clouds collide and compress. Smaller galaxies can be torn apart and assimilated into larger ones, sometimes leaving behind an irregular remnant. These interactions are essential in understanding the life cycle of galaxies and how they evolve over time.
Magellanic Clouds
The Magellanic Clouds are perhaps the most famous examples of irregular galaxies. They are two satellite galaxies of the Milky Way known as the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). Located relatively close to Earth, these clouds are visible with the naked eye from the Southern Hemisphere. The Magellanic Clouds provide a nearby example of irregular galaxies, allowing astronomers to study their properties in detail. Through their observations, researchers have learned a lot about the processes of star formation, galactic composition, and the effects of gravitational interactions within these unique galactic entities.

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Most popular questions from this chapter

If a luminous quasar has a luminosity of \(2 \times 10^{41} \mathrm{W}\), or \(\mathrm{J} / \mathrm{s}\), how many solar masses \(\left(M_{\circ}=2 \times 10^{30} \mathrm{kg}\right)\) per year does this quasar consume to maintain its average energy output?

\(\mathbf{T} / \mathbf{F}: A\) spiral galaxy's dark matter is distributed spherically.

The differences among various types of AGNs are caused by a. the type of the host galaxy. b. the size of the central black hole c. the amount of dark matter in the galaxy's halo. d. the viewing angle.

A rotation curve plots ______ versus distance from the galaxy center. a. orbital speed b. radial speed c. luminosity d. luminous mass

In spiral galaxies, stars form primarily in the spiral arms a. because that's where most of the mass of the galaxy is. b. because of the sudden increase in density. c. because that's where rotation is the fastest. d. because of conservation of angular momentum.
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