lecture 21, november 16, 2010 astr 101, section 3 instructor, jack brandt jcbrandt@unm.edu 1astr...

ASTR 101-3, FALL 2010 1

LECTURE 21, NOVEMBER 16, 2010

ASTR 101, SECTION 3INSTRUCTOR, JACK BRANDT

jcbrandt@unm.edu

ASTR 101-3, FALL 2010 2

ASTR 101-3, FALL 2010 3

ASTR 101-3, FALL 2010 4

ASTR 101-3, FALL 2010 5

ASTR 101-3, FALL 2010 6

ASTR 101-3, FALL 2010 7

ASTR 101-3, FALL 2010 8

ASTR 101-3, FALL 2010 9

a) measuring distances with Cepheid variable stars.

b) identifying the mass of the Galaxy’s central black hole.

c) determining the masses of stars in an eclipsing binary system.

d) using spectroscopic parallax to measure distances to stars.

Question 3

The period – luminosity relationship is a crucial component of

a) measuring distances with Cepheid variable stars.

b) identifying the mass of the Galaxy’s central black hole.

c) determining the masses of stars in an eclipsing binary system.

d) using spectroscopic parallax to measure distances to stars.

Question 3

The period – luminosity relationship is a crucial component of

Cepheid variable stars with longer periods have higher actual

luminosities; short-period Cepheids are dimmer.

ASTR 101-2, SPRING 2006

ASTR 101-3, FALL 2010 13

ASTR 101-3, FALL 2010 14

a) supernova remnants.b) white dwarf stars in the spiral arms.c) red giant variable stars in globular clusters.d) bright O and B stars in open clusters.e) X-ray sources.

Question 1

The location of the galactic center was identified using

a) supernova remnants.b) white dwarf stars in the spiral arms.c) red giant variable stars in globular clusters.d) bright O and B stars in open clusters.e) X-ray sources.

Question 1

The location of the galactic center was identified using

Harlow Shapley used pulsating RR-Lyrae variables as distance indicators to the

globular clusters.

He then deduced the distance and direction of the Milky Way’s center.

ASTR 101-3, FALL 2010 17

ASTR 101-3, FALL 2010 18

ASTR 101-3, FALL 2010 19

ASTR 101-3, FALL 2010 20

ASTR 101-3, FALL 2010 21

a) the spiral arms formed first.b) the globular clusters formed first.c) the disk component started out thin and

grew.d) spiral density waves formed first.e) the bar in the bulge formed first.

Question 7

In the formation of our Galaxy

a) the spiral arms formed first.b) the globular clusters formed first.c) the disk component started out thin and

grew.d) spiral density waves formed first.e) the bar in the bulge formed first.

Question 7

In the formation of our Galaxy

Globular clusters contain very old stars, no gas or dust, and

orbit around the center randomly.

ASTR 101-3, FALL 2010 24

ASTR 101-3, FALL 2010 25

a) a spiral galaxy.b) a barred spiral galaxy.c) an elliptical galaxy.d) a quasar.e) an irregular galaxy.

Question 5

Detailed measurements of the disk suggest that our Milky Way is

a) a spiral galaxy.b) a barred spiral galaxy.c) an elliptical galaxy.d) a quasar.e) an irregular galaxy.

Question 5

Detailed measurements of the disk suggest that our Milky Way is

Measurements of stellar motion in and near the bulge imply that it is football shaped, about half as wide as it is long,

characteristic of a barred spiral galaxy.

ASTR 101-3, FALL 2010 28

ASTR 101-3, FALL 2010 29

ASTR 101-3, FALL 2010 30

ASTR 101-3, FALL 2010 31

ASTR 101-2, SPRING 2006

ASTR 101-3, FALL 2010 33

a) the Sun’s mass and velocity in orbit around the galactic center

b) the rotation of the bulge and disk components

c) the Sun’s age and age of globular cluster stars

d) the motion of spiral arms and the mass of the central black hole

e) the Sun’s orbital period and distance from the center

Question 6

What two observations allow us to estimate the Galaxy’s mass?

Question 6

What two observations allow us to estimate the Galaxy’s mass?

Use the modified form of Kepler’s law to find the mass:

Total mass = (orbital size)3 / (orbital period)2

a) the Sun’s mass and velocity in orbit around the galactic center

b) the rotation of the bulge and disk components

c) the Sun’s age and age of the globular cluster stars

d) the motion of spiral arms and mass of the central black hole

e) the Sun’s orbital period and distance from the center

Question 10

a) 21-cm maps of the spiral armsb) the rotation curve of the outer edges of

the Galaxyc) orbits of open clusters in the diskd) infrared observations of new star- forming

regionse) X-ray images of other galaxies

What suggests that the mass of our Galaxy extends farther than its visible disk?

a) 21-cm maps of the spiral armsb) the rotation curve of the outer edges of

the Galaxyc) orbits of open clusters in the diskd) infrared observations of new star- forming

regionse) X-ray images of other galaxies

Question 10

What suggests that the mass of our Galaxy extends farther than its visible disk?

The outer edges of the Galaxy’s disk rotate much faster than

they should.

Most of the mass of the Galaxy must be dark matter.

ASTR 101-3, FALL 2010 38

ASTR 101-3, FALL 2010 39

ASTR 101-3, FALL 2010 40

ASTR 101-3, FALL 2010 41

a) tidal forces from the Andromeda Galaxy.b) accretion disks around neutron stars.c) gamma-ray bursts.d) gravitation from globular clusters.e) a supermassive black hole.

Question 4

High-speed motion of gas and stars near the Milky Way Galaxy’s center is explained by

Question 4

High-speed motion of gas and stars near the Milky Way Galaxy’s center is explained by

Recent observations estimate the black hole to be 4 million solar

masses.

a) tidal forces from the Andromeda Galaxy.b) accretion disks around neutron stars. c) gamma-ray bursts.d) gravitation from globular clusters.e) a supermassive black hole.

ASTR 101-3, FALL 2010 44