Question

• a ______ is a massive system of ______, gas, and dust.
• galaxies are classified by their ________.
• normal galaxies include spiral, elliptical, and irregular

Explanation:

These are fill-in-the-blank questions about astronomical concepts related to galaxies. A galaxy is defined as a large system containing stars, gas, and dust. Galaxies are categorized based on their shapes, with common types being spiral, elliptical, and irregular.

Answer:

• A galaxy is a massive system of stars, gas, and dust.
• Galaxies are classified by their shape/structure.