ASTR 1346:Chapter 11
101 Cards in this Set
| Front | Back |
|---|---|
|
How to measure Stars
|
- distance
- luminosity/brightness
- temperature
- size
- evolutionary stage (H-R diagram)
- mass
|
|
A full circle contains __ degrees
|
360o
|
|
1o = __ arc min
|
60'
|
|
1' = ___ arcsec
|
60"
|
|
Ways to measure apparent size and position of the objects
|
degree, arc min, arc sec
|
|
The family of distance-measurement techniques used by astronomers to chart the universe
|
cosmic distance scale
|
|
For nearby stars, we use __ method
|
Stellar Parallax method
|
|
The apparent displacement of foreground object relative to a distant background as the observer's position changes
|
parallax
|
|
Inversely proportional to distance
|
parallax
|
|
Formula for Distance (pc)
Unit of distance; defined as a distance at which parallax angle (the shift) is 1 arcsec (1")
|
parsec
|
|
1 Parsec = __ light years
|
3.3 light years
|
|
1 Parsec = ___ AU
|
206,265
|
|
For measuring the distances of the planets of our Solar System, we use ___ as a baseline
|
earth's diameter
|
|
For measuring the distance of nearby stars we use ___ as a baseline
|
earth's orbit
|
|
According to the spectrum, stars are classified into following categories (temperature sequence)
|
O, B, A, F, G, K, M, L, T
temp decreasing ->
|
|
Scientists used to classify stars based on their hydrogen line intensities, but now they classify stellar spectra based on ___
|
temperature
|
|
Temperature of "O" stars
|
30,000 K
|
|
Temperature of "B" stars
|
20,000 K
|
|
Temperature of "A" stars
|
10,000 K
|
|
Temperature of "F" stars
|
7,000 K
|
|
Temperature of "G" stars
|
6,000 K
|
|
Temperature of "K" stars
|
4,000 K
|
|
Temperature of "M" stars
|
3,000 K
|
|
Temperature of "L" stars
|
1,300 - 2,500 K
|
|
Temperature of "T" stars
|
< 1300 K
|
|
Failed Star
|
"T" type star
|
|
Sun is __ star
|
G2
|
|
Barnard star is a ___ star
|
M5
|
|
Astronomers further subdivide each spectral classification into __ subdivisions
|
10
|
|
Which is hotter & cooler star - G0 G1 G2 G3 G4 G5 G6 G7 G8 G9
|
G0 = hotter star
G9 = cooler star
|
|
Which type of stars are smallest in size?
|
"M" stars
|
|
Which type of star is the largest star?
|
"O" stars
|
|
We can estimate a star's effective temperature from its ___ or ___
|
spectral type or black body curve
|
|
We can estimate a stars luminosity from its ___ and ____
|
apparent brightness and distance
|
|
We can estimate a stars radius from ____
|
radius-luminosity-temperature relationship
|
|
Differences in Stellar Spectra are only due to ___
|
different temperatures
|
|
Is there a correlation between temperature and luminosity?
|
Yes
|
|
(1912) Danish astronomer Eljnar Hertzsprung and American astronomer Henry Norris Russell studied nearby stars to determine what?
|
correlation between temperature and luminosity
|
|
Plot of temperature and luminosity
|
HR Diagram
|
|
On HR Diagram, what is on the horizontal axis?
|
temperature; hottest to coolest
|
|
On HR Diagram, what is on the vertical axis?
|
luminosity; faintest to brightest
|
|
HR Diagram is also called __
|
color-magnitude diagram
1. supergiants
2. giants
3. main sequence
4. white dwarfs
5. luminosity (Lsun)
6. temperature (K)
|
|
Majority of stars that lie along a diagonal band in the HR-Diagram
|
main sequence stars
|
|
What percent of stars are Main Sequence Stars?
|
90%
|
|
Most of the stars on Main Sequence of HR-Diagram are __
|
red dwarfs
|
|
K and M stars with low luminosity
|
red dwarfs
|
|
A few of the stars on Main Sequence of HR-Diagram are __
|
blue giants
|
|
Hot, luminous stars
|
blue giants
|
|
Very few of the stars on Main Sequence of HR-Diagram are __
|
blue supergiants
|
|
Very hot and very luminous stars
|
blue supergiants
1. blue giants
2. red dwarfs
|
|
Very hot but very faint
|
white dwarfs
|
|
Stars on lower left of HR diagram
|
white dwarfs
|
|
Stars that must have smaller radius
|
white dwarfs
|
|
Stars that are much fainter and smaller than Main Sequence stars of the same temperature
|
white dwarfs
|
|
Cool but very luminous
|
red giants
|
|
Stars on upper right of HR-Diagram
|
red giants
|
|
Stars that must have much larger radius
|
red gaints
|
|
Stars that are much brighter and bigger than MS stars of the same temperature
|
red giants
1. blue giants
2. luminosity
3. main sequence
4. white dwarfs
5. temperature
6. main sequence
7. red giants
8. red supergiants
|
|
Indicate stellar radii (HR-Diagram)
|
dashed diagonal lines
|
|
For stars of the same radius (size), hotter stars are ___
|
more luminous than cooler stars
|
|
Radius-Luminosity- Temperature Relationship Formula
|
luminosity is directly proportional to radius square and temperature to the power four
|
|
____ gives us the information about the density of stars
|
width of the lines in the spectrum
|
|
By studying ___ we can distinguish the main sequence stars from other types of stars like gaints, dwarfs etc.
|
width of lines
|
|
Categorization of Stars
|
luminosity class
|
|
Tells us the approximate location of star on HR-Diagram
|
full spectral classification
|
|
The Sun's classification
|
G2V (G2 main-sequence star)
|
|
Betelguese's classification
|
M2Ib (M2 supergiant star)
|
|
Rigel's classification
|
B8Ia (B8 bright supergiant star)
|
|
Sirius's classification
|
A1V (A1 main-sequence star)
|
|
Alebaran's classification
|
K5III (K5 giant star)
|
|
Bright supergiants
|
Ia
|
|
Supergiants
|
Ib
|
|
Bright giants
|
II
|
|
Giants
|
III
|
|
Subgiants
|
IV
|
|
Dwarfs (MS stars)
|
V
|
|
This diagram is called
|
luminosity class
1. luminous supergiant; 2. Ia
3. less luminous supergaint; 4. Ib
5. bright giants; 6. II
7. giants; 8. III
9. subgiants; 10. IV
11. main sequence; 12. V; 13. sun
14. surface temperature
15. luminosity
16. absolute magnitude
17. spectral type
|
|
From O-K temperature ___ (decreases/increases)
|
decreases
|
|
The hotter the star, the ___
|
brighter it is
|
|
The cooler the star, the ___
|
fainter it is
|
|
__% of stars are main sequence stars
|
99%
|
|
Extremely hot, dim stars
|
white dwarfs
|
|
Extremely bright, low temperature stars
|
red giant
|
|
Difference between white dwarf and red giant is due to ___
|
size
|
|
___ relationship in Paralax
|
inverse
|
|
Shift in parallax becomes lesser and lesser as we __
|
move away
|
|
To increase shift in parallax, you need to __
|
increase baseline
|
|
Largest baseline we can get on Earth
|
poles (any diagonally opposite points)
|
|
__" = 1o
|
3600"
|
|
1" = width of a ___
|
dime; 1 1/4 miles away
|
|
Distance were parallax angle (the shift) is 1 arcsec (1")
|
1 parsec (pc)
|
|
If a Star A has more distance than Star B - Star A would have ___ parallax angle than Star B
|
smaller
|
|
Star X has a parallax angle of 5" and Star Y has an parallax angle of 10"
|
Star X is twice as far as Star Y
|
|
The smaller the angle, the ___ the star
|
further
|
|
(T/F) The closer the distance, the smaller the angle
|
FALSE
|
|
Star A is 3 parsecs away; Star B is 9.9 light years away. Which star is closer?
|
Both stars are same distance
|
|
Star A has a parallax of 3 arcsec. How far away is it in parsecs?
|
Star is 1/3 (0.33) parsecs away
|
|
Star X has parallax of 0.2 arcsec; Star Y has 2 arcsec. Which star is closest to Earth?
|
Star Y
|
|
Stars that are blue
|
O, B, A type stars
|
|
Stars that are red
|
M type stars
|
|
Stars that are yellow
|
K, G, F type stars
|
ASTR 1346:Chapter 11