Galaxy Classification Flashcards

Spiral Galaxies

• Milky Way: Composed of a bulge, disk, and halo; Earth is positioned about two-thirds out from the center in the disk.
• Whirlpool Galaxy: Features enhanced star formation in its disk due to interactions with a nearby galaxy. The dark regions indicate silicon and carbon dust blocking starlight, while heated hydrogen gas contributes to its red color.

Bulge

• Consists primarily of older red stars residing in the central region of spiral galaxies.

Spiral Arms

• Characterized by the presence of both young blue stars and older stars, contributing to the galaxy's luminosity and structure.

Spiral vs. Elliptical Galaxies

• Spiral galaxies contain more gas, dust, and ongoing star formation compared to elliptical galaxies.
• Spiral galaxies are recognizable by their disks, whereas elliptical galaxies lack this distinct structure.

Galaxy Classifications

• Spiral galaxies can be categorized as S (non-barred) or SB (barred) based on the presence of a central bar.
• Further classification divides these into types "a," "b," or "c," with type "c" having loose, lumpy arms and a smaller bulge than type "a".

SBa Galaxy

• Describes a barred spiral galaxy that features tight, smooth arms and has a relatively large bulge.

Elliptical Galaxies

• Classified from E0 (circular) to E7 (elongated) based on their appearance and shape in the sky.

Irregular Galaxies

• Galaxies that do not fit into the spiral or elliptical categories, known as irregulars, display a more chaotic structure.

Tadpole Galaxy

• Exhibits a distorted shape due to a collision with another small galaxy, leaving behind tidal debris from the gravitational interaction.

Star Clusters

• Formed from gas resulting from galaxy collisions, often showcasing young, massive blue stars due to high star formation rates in such regions.

Galaxy Collisions

• The likelihood of individual stars or planets colliding during galaxy encounters is extremely low due to the vast distances between them.

Mergers

• The merger of two spiral galaxies can lead to the formation of an elliptical galaxy, demonstrating a significant evolutionary process in galaxy formation.