09 Galaxies and Their Evolution Free Online FlashCards

What structure characterizes a spiral galaxy?

A spiral galaxy has a flattened disk, often with spiral arms, around a central bulge.

How did dark matter halos help galaxies form?

Dark matter halos helped attract ordinary matter, especially gas. As gas accumulated, it could cool, settle, and form stars.

What powers an active galactic nucleus (AGN)?

An AGN is a compact, exceptionally energetic region at a galaxy’s center, powered by matter falling toward a supermassive black hole.

What is the cosmic web?

The cosmic web is the large-scale pattern of filaments, sheets, and dense intersections, separated by vast voids with relatively few galaxies.

What type of galaxy is the Milky Way?

The Milky Way is a barred spiral galaxy, with an elongated bar in its central region.

How do elliptical galaxies typically differ from spirals?

Elliptical galaxies range from nearly round to elongated and generally have less cold gas and dust than spirals.

What distinguishes a lenticular galaxy?

A lenticular galaxy has a disk and central bulge but lacks prominent spiral arms; it tends to have older stars and little current star formation.

What defines an irregular galaxy?

Irregular galaxies lack a clear spiral or elliptical structure. Some are gas-rich, while others have been distorted by gravitational encounters.

How can galaxies grow after their initial formation?

Galaxies grow by acquiring gas and merging with smaller systems, as well as through star formation and other processes.

What do stellar winds and supernovae return to their surroundings?

Stellar winds and supernovae return energy and elements to a galaxy’s surroundings, influencing its gas and star formation.

What usually happens to stars during a galaxy merger?

Stars usually pass without directly colliding because the distances between them are enormous, though gas clouds can interact.

Do all galaxies follow one path from irregular to spiral to elliptical?

A simple progression from irregular to spiral to elliptical is not a universal rule; galaxy histories vary, and some disks survive encounters or form again.