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Pathways to Astronomy

Stephen E. Schneider

Chapter 77

Active Galactic Nuclei - all with Video Answers

Educators

Chapter Questions

01:46

Problem 1

If a quasar is generating 10,000 times more luminosity than a galaxy, how many times farther away would it be if it appeared to be the same brightness as the galaxy?

Farhanul Hasan
Farhanul Hasan
Numerade Educator
03:51

Problem 2

The radius of a black hole is approximately $3 \mathrm{km}$ times the mass of the black hole in solar masses (Unit 68).
a. Find the diameter in $A U$ of a black hole with a mass of 1 billion $M_{\odot}$
b. For an accretion disk 10 times the radius of the black hole in (a), how many light-hours across would it be?

Ajay Singhal
Ajay Singhal
Numerade Educator
02:29

Problem 3

Hydrogen has a spectral line at $122 \mathrm{nm}$ in the ultraviolet portion of the spectrum. What are the largest and smallest redshifts a quasar could have for this line to be seen in the visible portion of the spectrum (400 to 700 $\mathrm{nm}$ )?

Ashley Moorman
Ashley Moorman
Numerade Educator
01:35

Problem 4

An AGN is observed to double in brightness over seven days and then to grow dim again in the next seven days. What is an upper limit to the probable size of the AGN? Give your result in AU.

Farhanul Hasan
Farhanul Hasan
Numerade Educator
01:46

Problem 5

A quasar has a brightness that corresponds to apparent magnitude 15 (Unit 54.4 ). If it is 1 billion $\mathrm{pc}$ away, how many times brighter than the Sun is it? How does this compare to the brightness of the Milky Way?

Farhanul Hasan
Farhanul Hasan
Numerade Educator
04:21

Problem 6

The hydrogen line of gas orbiting in the nucleus of an active galaxy is Doppler shifted on the right side of the AGN to $123 \mathrm{nm},$ and on the left side to $121 \mathrm{nm}$. How fast is the gas rotating?

Zulfiqar Ali
Zulfiqar Ali
Numerade Educator