Quizlet

Question 1

Apparent brightness =

Answer 1

Luminosity / distance^2

Question 2

Larger magnitudes are?

Answer 2

Dimmer

Question 3

Radiation from stars is:

Answer 3

Blackbody radiation

Question 4

Stellar spectra are much more informative than the black body curves

Answer 4

True

Question 5

Spectral class from highest to lowest

Answer 5

(Hottest) O, B, A, F, G, K, M (coolest)

Question 6

Blackbody spectrum:

Answer 6

Radiation emitted by an object depending only on its temperature

Question 7

Wiens law:

Answer 7

Peak wavelength is inversely proportional to temperature

Question 8

Total energy (per area and time) emitted is proportional to the 4th power of:

Answer 8

Temperature F (energy per area per unit time) = sigmaT^4

Question 9

Spectroscopic parallax:

Answer 9

Nothing to do with parallax but does use spectroscopy in finding the distance to a star

Question 10

Spectroscopic parallax

Answer 10

1. Measure the stars apparent magnitude and spectral class
2. Use spectral class to estimate luminosity
3. Apply inverse square law to find distance

Question 11

Stellar luminosity classes

Answer 11

Ia: bright super giants

Ib: supergiants

II: bright giants

III: giants

IV: Subgiants

V: Main-sequence stars and dwarfs

Question 12

Binary stars are:

Answer 12

Two stars orbiting a common center of mass

Question 13

Which star in a binary star is the primary star and which is the secondary star (A and B)

Answer 13

The brighter star is the primary and the dimmer is the secondary

Question 14

Wide binaries:

Answer 14

Are stars that have orbits that keel them spread apart from one another

Question 15

Close binaries:

Answer 15

Evolve nearby and transfer mass from one to the other

The primaries sometimes consume the material from companion or the whole star

Question 16

Binary systems provide:

Answer 16

The best means for scientists to determine the mass of the star

Question 17

As the pair of binary stars pull on eachother astronomers can calculate size and from there determine what:

Answer 17

Temperature and radius

Question 18

Distance to nearest stars can be measured by:

Answer 18

Parallax

Question 19

Apparent brightness is as observed from earth

Answer 19

Depends on distance and absolute luminosity

Question 20

Spectral classes corespondent to:

Answer 20

Different surface temperatures

Question 21

Stellar size is related to luminosity and temperature

Answer 21

True

Question 22

Mass determines:

Answer 22

Where a star lies on the main sequence

Question 23

Star formation happens when a part of a dust cloud begins to contract under its own gravitational force:

Answer 23

As it collapses the center becomes hotter and hotter until nuclear fusion begins at the core

Question 24

Stars can be as big or as small as:

Answer 24

.075 solar masses and 150 solar masses

Question 25

Dark dust clouds are dark because:

Answer 25

Starlight from behind the cloud does not penetrate the cloud

Question 26

Interstellar gas composed of:

Answer 26

90% hydrogen 9% helium

Question 27

Star formation begins with:

Answer 27

Fragmenting collapsing cloud of dust and gas

Question 28

Brown dwarves never become stars

Answer 28

True :(

Question 29

During its stay on the main sequence a star is in:

Answer 29

Equilibrium

Question 30

Helium fusion occurs when the core temperature reaches:

Answer 30

1000,000,000 K

Question 31

Red giants never become hot enough for fusion past carbon to take place

Answer 31

True