Structure
Spiral galaxies consist of four distinct components:
- A flat, rotating disc of (mostly newly created) stars and interstellar matter
- A central stellar bulge of mainly older stars, which resembles an elliptical galaxy
- A near-spherical halo of stars, including many in globular clusters
- A supermassive black hole at the very center of the central bulge
The relative importance, in terms of mass, brightness and size, of the different components varies from galaxy to galaxy.
Read more about this topic: Spiral Galaxy
Famous quotes containing the word structure:
“What is the structure of government that will best guard against the precipitate counsels and factious combinations for unjust purposes, without a sacrifice of the fundamental principle of republicanism?”
—James Madison (1751–1836)
“A special feature of the structure of our book is the monstrous but perfectly organic part that eavesdropping plays in it.”
—Vladimir Nabokov (1899–1977)
“Science is intimately integrated with the whole social structure and cultural tradition. They mutually support one other—only in certain types of society can science flourish, and conversely without a continuous and healthy development and application of science such a society cannot function properly.”
—Talcott Parsons (1902–1979)