Unit 8: Characterizing Stars

Question 1

Why do stars appear in different colors?

Answer 1

because of their temperature

Question 2

What is an Astronomical Unit

Answer 2

The average distance between the earth and sun

Question 3

What is a Light Year

Answer 3

The distance that light travels in a vacuum in one year

Question 4

What is a Parsec

Answer 4

1 pc= 3.26

Question 5

What is the most convenient measurement for measuring interstellar and inter galaxies distance

Answer 5

• Light year and Parsec

Question 6

What are the properties of interest of Stars

Answer 6

Distance
Visible brightness
luminosity 
surface temperature
size
age
mass

Question 7

What is the Parallax Method used for?

Answer 7

This is a measurement of the distances to nearby stars

• This method only works for closer and nearby stars
• not more than 1000 pc away from the earth

Question 8

The Parallax Method is the only method allowing what?

Answer 8

Only method allowing to express distances to stars in terms of diameter of Earth’s orbit.

Question 9

When was the first parallax measurement made? By who?

Answer 9

1838 by Friderich Wilhem Bessel

Question 10

What is Apparent Magnitude?

Answer 10

The brightness of stars without regard to their distances
(m)
the brightness of stars as seen from Earth

Question 11

Objects which are brighter than first-magnitude stars have apparent magnitudes ______ than 1, even _______ ones.

Answer 11

1. Less

2. Negative

Question 12

What is the apparent magnitude of Sirius

Answer 12

This is the brightest star in the night sky, has a negative apparent magnitude: m= -1.44

Question 13

What is the apparent magnitude of Venus

Answer 13

m= -4.4

Question 14

What are the Moon and Sun’s apparent magnitudes

Answer 14

Moon (-12.6)

Sun (-26.7)

Question 15

What is the contemporary measurement of an apparent magnitude based on?

Answer 15

Electronic devices directly measuring an intensity of light

Question 16

What us the naked eye limit of apparent magnitude

Answer 16

+6.0

Question 17

What is a star’s absolute magnitude

Answer 17

M

The stars apparent magnitude the star would have if it were 10 pc from the Earth

Question 18

What is the range of absolute magnitude

Answer 18

Absolute magnitude range from roughly M= -10 for the brightest stars to M= +17 for the dimmest

Question 19

What is Luminosity

Answer 19

the total amount of energy radiating from the star’s surface each second

Question 20

The absolute magnitude of a star and its luminosity are _____ _________.

Answer 20

directly proportional

Question 21

What is the Harvard Classification Scheme and who created it?

Answer 21

The first serious attempt to organize and classify stars based on their temperatures
- Edward Charles Pickering and Annie Jump Cannon

Question 22

What are the Stellar Classes

Answer 22

O, B, A, F, G, K, M,
0= coldest (blue violet)
M= hottest (red-orange)

Question 23

What does the Hertzsprung-Russell Diagram show

Answer 23

that stars luminosity and surface temperature are correlated

Question 24

What percent of stars belong to the main sequence band

Answer 24

over 90%

Question 25

What does the lower right side of the Hertzsprung-Russell Diagram show

Answer 25

• dim and red

Question 26

What does the top left side of the Hertzsprung-Russell Diagram show

Answer 26

• cold and bright

Question 27

Where are White Dwarfs on the Hertzsprung-Russell Diagram

Answer 27

bottom left

High mass and low luminosity

Question 28

Where is the sun on the Hertzsprung-Russell Diagram

Answer 28

in the main sequence band

Question 29

Where are the super giants on the Hertzsprung-Russell Diagram

Answer 29

top right

low temperature, high luminosity

Question 30

What is the Spectroscopic Parallax

Answer 30

the indirect method for the measurement of distances to stars.

Question 31

What kind of stars can the Spectroscopic parallax be applied to

Answer 31

any main sequence star

~10,000parsec

Question 32

What are Cepheid Variables and what can it be used for

Answer 32

Stars which brighten and dim periodically.

- allows them to be used as cosmic yardsticks out to distances of a few thens of millions of LY

Question 33

What are the steps to determine main sequence stars distance

Answer 33

1. Determine the spectro class (line up from the bottom of the chart in line with the start to the main sequence line)
2. Absolute Magnitude M
3. Apparent Magnitude m

Question 34

How/when were Cepheid Stars discovered

Answer 34

absolute magnitude combined with apparent magnitude = distance

Question 35

What are Optical Doubles/Apparent Binaries

Answer 35

Physically far from each other. They are unrelated stars that appear close together thought chance alignment with Earth

Question 36

What are Binary Stars?

Answer 36

Stars that are physically close and form the system

- two stars that orbit each other

Question 37

How many stars in the sky are Binary stars

Answer 37

1/3 to half of the stars in the sky

Question 38

What are visual binary stars vs Spectroscopic Binary

Answer 38

Visual are seen separately by telescopes and spectroscopic are hard to see separately even with telescope

Question 39

What is the Big Dipper Constellation called

Answer 39

Ursa Major

- is a binary star

Question 40

What does Keplers Law tell us

Answer 40

the combined mass of binary stars

Question 41

More luminous stars are _____?

Answer 41

Bigger