Chapter 17/18/19: Measuring Properties of Stars

Question 1

What is a Parallax?

Answer 1

uses the change in the object’s apparent position, compared to the background.

Question 2

What is a Stellar Parallax?

Answer 2

the parallax of the star is equal to teh angular radius of the Earth’s orbit as seen from the star. (closer = greater angle)

Question 3

What is a parsec?

Answer 3

the parallax angle of that star in arcseconds.

Question 4

1pc

Answer 4

3.26 ly

Question 5

If p = 1 arcsecond

Answer 5

d = 1 parsec

Question 6

What is Luminosity/Intrinsic Brightness?

Answer 6

measure of the total energy radiated by a star (energy/second)

Question 7

What is Apparent Brightness?

Answer 7

how bright a star appears when viewed from Earth (depends on luminosity and distance)

Question 8

What is brightness?

Answer 8

the amount of light arriving at a particular place.

Question 9

What is the inverse square law of radiation?

Answer 9

Brightness decreases as the distance from the light source increases. Light spreads out over a greater area.

Question 10

What is Wein’s law?

Answer 10

Red stars are cooler, blue stars are hotter

Question 11

What are the spectral classes? (hottest to coolest)

Answer 11

O, B, A, F, G, K, M

Question 12

What is the absorption line spectra?

Answer 12

it is what the atmosphere of stars produces depending on different elements.

Question 13

What determines what we see in the star’s spectrum?

Answer 13

The star’s surface temperature.

Question 14

What is a Brown Dwarf?

Answer 14

Objects with masses less then 7.5% of our Sun, not hot enough for hydrogen fusion to take place. (LYT)

Question 15

What do Brown Dwarfs burn at their core?

Answer 15

Deuterium.

Question 16

What are binary stars?

Answer 16

Stars that orbit each other (can help measure their masses)

Question 17

What theory do binary stars use?

Answer 17

Newton’s theory of gravity

Question 18

What law can be applied to any 2 orbiting objects?

Answer 18

Kepler’s Third Law of Planetary Motion

Question 19

What kinds of binary stars are there?

Answer 19

Visual binaries, Spectroscopic binaries, Eclipsing binaries, Astrometric binaries

Question 20

What is a Visual Binary?

Answer 20

They can be measured directly and both are observed through a telescope.

Question 21

What is a Spectroscopic Binary?

Answer 21

Can be measured using their Doppler shifts. (spectral lines move back and forth as stars move towards and away as they orbit)

Question 22

What is an Eclipsing Binary?

Answer 22

Can be used to measure star size by observing how long the eclipse takes by using their distance from each other.

Question 23

What is an Astrometric Binary?

Answer 23

Stars wobble in their proper motion periodically due to gravitational influence

Question 24

What is the HR diagram (Hertzsprung-Russell)?

Answer 24

Plot of stellar luminosity vs surface temp (OBAFGKM).

Question 25

What is the Sun on the HR diagram?

Answer 25

Kind of in the middle (G-K and just above 1)

Question 26

What are the main regions?

Answer 26

Red Giants, Blue Giants, Red Dwarfs, White Dwarfs

Question 27

What is the main sequence?

Answer 27

Where most stars are.

Question 28

What is a Red Giant?

Answer 28

Cooler but still very luminous stars.

Question 29

What is a Blue Giant?

Answer 29

Hotter and very luminous stars.

Question 30

What is a Red Dwarf?

Answer 30

least massive main sequence stars and most common (cool and dim (under red giants)).

Question 31

What is a White Dwarf?

Answer 31

Stars that are hit and not luminous (under Blue giants (dim and hot)).

Question 32

What is the Mass-Luminosity Relation?

Answer 32

the greater the mass of the main sequence star the greater the luminosity.

Question 33

What is a stellar lifetime dependent on?

Answer 33

Mass

Question 34

The higher the mass…

Answer 34

The less the lifetime.

Question 35

What stars last the longest?

Answer 35

small red dwarfs.