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🪐intro to astronomy review

Triangulum Galaxy

Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025

Definition

The Triangulum Galaxy, also known as Messier 33 or NGC 598, is a spiral galaxy located in the constellation Triangulum. It is the third-largest member of the Local Group of galaxies, after the Andromeda Galaxy and the Milky Way.

Triangulum Galaxy cheat sheet for homework

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5 Must Know Facts For Your Next Test

  1. The Triangulum Galaxy is located approximately 2.73 million light-years from Earth, making it one of the most distant permanent objects visible to the naked eye.
  2. It has a diameter of about 60,000 light-years, making it the third-largest member of the Local Group after the Andromeda Galaxy and the Milky Way.
  3. The Triangulum Galaxy is receding from the Milky Way at a speed of approximately 179 km/s, as measured by its redshift.
  4. The Triangulum Galaxy is thought to have a central supermassive black hole, like many other spiral galaxies, though its mass is not well-constrained.
  5. Observations of the Triangulum Galaxy have provided insights into the distribution of dark matter and the formation of spiral arms in galaxies.

Review Questions

  • Explain how the Triangulum Galaxy's location and size within the Local Group relate to the concept of the expanding universe discussed in Topic 26.5.
    • The Triangulum Galaxy, as a member of the Local Group, is located approximately 2.73 million light-years from Earth. This distance, combined with the galaxy's measured redshift, which indicates it is receding from the Milky Way at a speed of 179 km/s, provides evidence for the expansion of the universe as described in Topic 26.5. The Triangulum Galaxy's size, being the third-largest member of the Local Group, also demonstrates the distribution of galaxies in space and the hierarchical structure of the universe, as discussed in Topic 28.3.
  • Analyze how the Triangulum Galaxy's spiral structure and the presence of a central supermassive black hole contribute to our understanding of the distribution of galaxies in space, as covered in Topic 28.3.
    • The Triangulum Galaxy's spiral structure, which is characteristic of many galaxies, provides insights into the formation and evolution of galaxies within the larger distribution of galaxies in space. Additionally, the presence of a central supermassive black hole in the Triangulum Galaxy, like in many other spiral galaxies, suggests that this feature is a common property of galaxies and plays a role in shaping their structure and dynamics. These observations help expand our understanding of the diverse distribution of galaxies in the universe, as discussed in Topic 28.3.
  • Evaluate how the study of the Triangulum Galaxy, including its distance, redshift, and relationship to the Local Group, has contributed to our overall understanding of the expanding universe and the distribution of galaxies in space, as covered in Topics 26.5 and 28.3.
    • The Triangulum Galaxy, as a member of the Local Group, has provided valuable insights that have contributed to our understanding of the expanding universe and the distribution of galaxies in space. The galaxy's distance of 2.73 million light-years and its measured redshift, indicating a recession speed of 179 km/s, support the concept of an expanding universe described in Topic 26.5. Additionally, the Triangulum Galaxy's size and position as the third-largest member of the Local Group demonstrate the hierarchical structure and distribution of galaxies in space, as discussed in Topic 28.3. Furthermore, the presence of a central supermassive black hole and the galaxy's spiral structure provide insights into the common features and dynamics of galaxies within the larger context of the universe's evolution and structure.
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