Section 14.B - Structure of a Galaxy Like Our Milky Way

Question 1

1. Identify the difference between Population I and Population II stars:

Answer 1

•  One of those populations is early first-generation stars while the other is more recently made or later-generation stars.
•  The surfaces of the earlier generation show fewer heavy types of atoms present (“heavy elements”). These stars were made out of almost exclusively light atoms.
•  The Sun is one of the later generations of stars, which have more heavy types of atoms mixed into their composition. Where did it get those heavy types of atoms from?

Question 2

Pick which component of a spiral galaxy matches a description you are given (bulge, disk, halo, and nucleus/core):

Answer 2

• Recall that the oldest stars make up the bulge and halo of a galaxy. They have the least amount of heavy types of atoms.
•  Later-generation or 2nd-generation stars formed from the mix of previously unused gas/dust with the dispersed remains of gas and dust from earlier stars that died (and these stars are found mainly in the disk part of a galaxy).

Question 3

 Be able to pick which statement is false about the disk or halo/bulge/nucleus of a galaxy:

Answer 3

• True statements about disk include it is flat, has gas/dust, has spiral arms, and has stars both young/old (Pop. I & II).
• Halo, bulge, and nucleus are round, have no spiral arms, are essentially just old stars, and have no appreciable gas/dust.
• The nucleus is the most dense central part of Bulge. Bulge, nucleus, and surrounding halo contain old red stars.

Question 4

Recognize that dark halo component of the galaxy extends far beyond the visible edges of our Milky Way galaxy.

Answer 4

• It appears to be made of much “dark matter” of unknown type.
• We know the “dark matter” must exist because we can detect what?