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Difficulty: EasyStars, Galaxies, and the Universe

Match each galaxy classification with its defining structural characteristic.

  • Spiral galaxyDisk-shaped system with prominent pinwheel arms and active star-forming regions
  • Elliptical galaxySmooth, oval or spherical system composed mainly of older stars with minimal gas
  • Irregular galaxyAsymmetrical system lacking a defined central bulge or symmetric pattern

Answer

Spiral galaxy matches with the disk-shaped system with pinwheel arms; Elliptical galaxy matches with the smooth, oval or spherical system of older stars; Irregular galaxy matches with the asymmetrical system lacking a defined pattern.
Astronomers classify galaxies into three primary structural types: spiral galaxies possess a central nucleus with spiraling arms in a flat disk; elliptical galaxies exhibit smooth, rounded distributions of older stars; irregular galaxies show chaotic, asymmetric forms without regular structure.

Step-by-Step Solution

1
Identify the structural definition of a spiral galaxy.
Spiral galaxies have flat disks with curved spiral arms containing abundant interstellar gas and new stars.
The defining geometric feature of spiral galaxies is their pinwheel structure.
2
Identify the structural definition of an elliptical galaxy.
Elliptical galaxies are smooth, rounded, or football-shaped clouds of mostly older stars with sparse interstellar gas.
They lack spiral arms and disk structure.
3
Identify the structural definition of an irregular galaxy.
Irregular galaxies lack standard geometric symmetry or central bulges.
Their chaotic morphology is typically caused by gravitational disruption or ongoing mergers.

Key Concept

Hubble classification of galaxies into spiral, elliptical, and irregular morphologies based on structural geometry and stellar population.
Estimated Time:45s
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Topics

Stars, Galaxies, and the Universe

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