Chapter 16

The factor that makes Cepheid variables particularly useful as standard candles is a. their distance. b. their spectral class. c. the inverse square relation. d. their position on the HR diagram. e. the period-luminosity relationship.

Which of the following structures is/are found in all spiral galaxies? Choose all that apply. a. disk b. bulge c. jets d. bar e. spiral arms

A galaxy is observed to be spheroid and to have increasing stellar density toward the center. What is its galaxy classification? a. spiral b. barred spiral c. lenticular d. elliptical e. irregular

A galaxy seen edge on is observed to have a disk and a bulge. What is its galaxy classification? a. spiral b. barred spiral c. either elliptical or barred spiral d. either spiral or elliptical e. either spiral or barred spiral

Which of the following galaxy types is most likely to be clearly identifiable, regardless of orientation? a. E0 b. Irr \(c . \mathrm{SBa}\) d. E6 e. SBc

Which of the following is/are not among the subcategories of spiral galaxies? Choose all that apply. a. elliptical b. halo c. flocculent d. barred e. grand design

Which of the following galaxy types has no discernible structure? a. Irr II b. \(\mathrm{E} 7\) c. Irr I d. Ienticular e. SBb

Which of the following cosmic distance ladder methods use(s) actual or apparent motion of objects to determine distance? Choose all that apply. a. Tully-Fisher law b. spectroscopic parallax c. Type Ia supernovas d. parallax e. Cepheid variables

Which of the following cosmic distance ladder methods uses cyclical changes in star's brightness over time to determine distance? a. Tully-Fisher law b. spectroscopic parallax c. Type Ia supernovas d. parallax e. Cepheid variables

Which method of determining distance would be most appropriate for a ground- based observer trying to find accurate distances out to approximately 100 pc? a. Tully-Fisher law b. spectroscopic parallax c. Type Ia supernovas d. parallax e. Cepheid variables

Hubble's law says that a. all galaxies are expanding. b. the more distant the galaxy is, the faster it appears to be receding from us. c. larger galaxies rotate faster. d. the larger the galaxy is, the faster it is receding. e. all galaxies that will ever exist already do exist.

Galaxy A is receding from us at \(x \mathrm{km} / \mathrm{s}\), while galaxy \(\mathrm{B}\) 's recession velocity is \(3 x \mathrm{km} / \mathrm{s}\). Based on Hubble's law, which statement is true? a. \(\mathrm{B}\) is \(1 / 3\) as far from us as \(\mathrm{A}\). b. \(\mathrm{A}\) is \(1 / 3\) as far from us as \(\mathrm{B}\). c. \(\mathrm{B}\) is 9 times as far from us as \(\mathrm{A}\). d. The relative positions of \(A\) and \(B\) depend on the types of galaxies they are. e. The relative positions of \(\mathrm{A}\) and \(\mathrm{B}\) depend on their size.

Which of the following is/are included in the AGN designation? Choose all that apply. a. Seyfert galaxies b. radio galaxies c. quasars d. lenticular galaxies e. blazars

Which of the following describe(s) characteristics of AGNs that point to a black hole as the central engine? Choose all that apply. a. compact size of the core b. abundance of dark matter c. relativistic velocity of jets d. short timescale for variability in brightness e. rapid star formation

True/False: The defining characteristics of spiral galaxies include disk and bulge.

What led astronomers to infer the existence of dark matter? a. infrared images showing galactic halos b. the presence of far more satellite galaxies than expected c. observations of dark nebulas d. unexpected results in galactic rotation curves e. the discovery of black holes

Astronomers determined that elliptical galaxies have dark matter by a. calculating that the average stellar orbital velocity is greater than the expected escape velocity based on the luminous matter. b. calculating that the expected escape velocity based on the luminous matter is greater than the average stellar orbital velocity. c. measuring star rotation speeds near the axis of the galaxy. d. measuring the galaxies' rotation curves. e. measuring the observed brightness versus the luminosity.

Speculate on the role that dust played in determining the distance to faraway objects such as the spiral nebulas.

What are the four main classes of galaxies? Describe the characteristics of each type.

Which of the four galaxy types commonly occur as dwarfs?

Which types of galaxies show active star formation?

Describe the stellar orbits in spiral versus elliptical galaxies.

What does the Hubble tuning-fork diagram describe?

What is the cosmic distance ladder, and what does it mean that each rung of the ladder has been used to calibrate the next-higher rung?

Describe each of the following methods for determining astronomical distances: parallax, spectroscopic parallax, Cepheid variables, TullyFisher law, Type Ia supernovas. How did each technique rely on the previous one for calibration?

Hubble's law describes a correlation between what two quantities?

Define the following terms: \(A G N\), Seyfert galaxy, radio galaxy, quasar.

What evidence do astronomers have that AGNs are associated with supermassive black holes?

What is the evidence for dark matter in spiral galaxies? in elliptical galaxies?

How might people's outlook and understanding have changed upon learning that ours was not the only galaxy in the Universe?

The wavelength in the laboratory for a particular spectral line is \(580 \mathrm{nm} .\) It is observed in the spectrum of a galaxy at \(660 \mathrm{nm}\) What is the recession velocity of the galaxy, in kilometers per second?

What is the mass, in kilograms, of a black hole whose Schwarzschild radius is \(4.3 \times 10^{9} \mathrm{km}\) ?

Calculate the mass, in \(M_{\mathrm{Su}}\), of a black hole with Schwarzschild radius \(7.0 \times 10^{11} \mathrm{km}\)