Chapter 14: Problem 4

What is the Hubble classification scheme? Which category includes the largest galaxies? Which includes the smallest? Which category of galaxy is the most common?

Short Answer

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Answer: The Hubble classification scheme is a system used to classify galaxies based on their appearance and structure, dividing them into elliptical, spiral, and irregular galaxies. The largest galaxies are found in the elliptical category, specifically giant elliptical galaxies. The smallest galaxies are dwarf galaxies, with dwarf elliptical galaxies being the most common type. Spiral galaxies, including normal and barred spiral galaxies, are the most common category in the universe, making up approximately 70% of all observed galaxies.

Step by step solution

Hubble Classification Scheme: Overview

The Hubble classification scheme is a system used to classify galaxies based on their appearance and structure. The scheme divides galaxies into three main groups: elliptical galaxies, spiral galaxies, and irregular galaxies. These groups are further subdivided based on specific traits.

Largest Galaxies: Elliptical

The largest galaxies are found in the elliptical category. Elliptical galaxies are classified based on their degree of ellipticity, which is represented by a number ranging from E0 (which is nearly spherical) to E7 (which is highly elongated). The giant elliptical galaxies, particularly the ones with large degrees of ellipticity, are the largest galaxies in the universe.

Smallest Galaxies: Dwarf

The smallest galaxies are dwarf galaxies, which can be found in all three main groups (elliptical, spiral, and irregular). Dwarf elliptical galaxies (denoted as dE) are the most common type of dwarf galaxy and are smaller, less bright, and have a lower mass compared to their larger counterparts.

Most Common Category: Spiral

The most common category of galaxies is the spiral galaxies. Spiral galaxies are classified based on their degree of winding (tightness) and the size of their central bulge. There are two main types of spiral galaxies: normal spiral galaxies (denoted as S) and barred spiral galaxies (denoted as SB). Both types are further divided into subclasses a, b, and c based on the tightness of their arms and the size of their central bulge. Spiral galaxies are the most common type of galaxy in the universe, making up approximately 70% of all observed galaxies.

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What is the Hubble classification scheme? Which category includes the largest galaxies? Which includes the smallest? Which category of galaxy is the most common?

Short Answer

Step by step solution

Hubble Classification Scheme: Overview

Largest Galaxies: Elliptical

Smallest Galaxies: Dwarf

Most Common Category: Spiral

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