Test 3 Flashcards
What is an arc second?
the measurement of a parallax angle that is really small
What is an arc second?
the measurement of a parallax angle that is really small
What is a light year?
the distance light travels in one year
How does a light year compare to an parsec?
3 1/4 light years = 1 parsec
What is the system of stellar magnitudes?
O-B-A-F-G-K-M
how was the system originally set up?
it was originally based on the hydrogen absorbtion lines
Today a difference of 5 magnitudes corrisponds to what?
a factor in brightness of 100
What is the apparent magnitude?
measure how bright a star appears to be in the sky
what is absolute magnitude?
measure the intrinsic brightness of a star. Absolute magnitude equals what the apparent magnitude would be if the star was 10 parsecs away
What distance would a stars apparent brightness = the stars absolute magnitude?
at a distance of 10 parsecs away
what are the apparent and absolute magnitude of the sun?
Apparent = -26.7 Absolute = 4.8
What was the original system of classification based on?
it was based on hydrogen absorption lines
what is the order of bightness going from hot to cool?
O-B-A-F-G-K-M
in which spectral class of the stars are the absorption lines of hydrogen the strongest?
A
What is the spectral type of the sun?
G2
what is HR diagram?
shows the life cycle of a star
what is along the horizontal and vertical axis?
Horizontal = Temp at surface Vertical = Brigthness
what property of a star determines its position on the main sequence?
The mass
What are red giants?
stars in the process of dying
What are white dwarfs?
dead embers of stars
What is hydro static equilibrium?
every layer of a star has to be ina pressure balance between gravity that wants to pull the gas inward and internal pressure that wants to push the as outward.
how does the pressure in a star change when going from the surface of the star to the center?
the pressure will increase
in what two ways can a star transport energy outwards?
.
what one factor determines where a star will be found on the main sequence?
the mass of a star
how does the main sequence lifetime depend on the mass and luminosity of a star?
life time = mass / luminosity
What will be the total main sequence life time for the sun?
10 billion years
what will be the life time of a massive O star ?
1 million years
What about a low mass M star?
300 billion years
What is the ZAMS
Zero age main sequence
how is the core of a star changing during the entire main sequence lifetime
drastic changes on the inside cause smaller changes on the outside
in what 3 ways does the surface of a star change during its main sequence lifetime
its gets a little bigger, brighter and cooler
How can we tell the age of a star cluster?
.
when the neuclear reactions in the core end the core begins to the contract. Why?
.
how do you understand what happens to the core in terms of hydro static equilibrium?
.
as the core contracts there are now two energy sources in the center. what are they?
.
how does the energy from the stars center now compare to the energy produced when the star was on the main sequence?
.
what happens to the outer layers of the star?
.
What is a light year?
the distance light travels in one year
How does a light year compare to an parsec?
3 1/4 light years = 1 parsec
What is the system of stellar magnitudes?
O-B-A-F-G-K-M
how was the system originally set up?
it was originally based on the hydrogen absorbtion lines
Today a difference of 5 magnitudes corrisponds to what?
a factor in brightness of 100
What is the apparent magnitude?
measure how bright a star appears to be in the sky
what is absolute magnitude?
measure the intrinsic brightness of a star. Absolute magnitude equals what the apparent magnitude would be if the star was 10 parsecs away
What distance would a stars apparent brightness = the stars absolute magnitude?
at a distance of 10 parsecs away
what are the apparent and absolute magnitude of the sun?
Apparent =
Absolute =
What was the original system of classification based on?
it was based on hydrogen absorption lines
what is the order of bightness going from hot to cool?
O-B-A-F-G-K-M
in which spectral class of the stars are the absorption lines of hydrogen the strongest?
A
What is the spectral type of the sun?
G2
what is HR diagram?
shows the life cycle of a star
what is along the horizontal and vertical axis?
Horizontal = Temp at surface Vertical = Brigthness
what property of a star determines its position on the main sequence?
.
What are red giants?
stars in the process of dying
What are white dwarfs?
dead embers of stars
What is hydro static equilibrium?
every layer of a star has to be ina pressure balance between gravity that wants to pull the gas inward and internal pressure that wants to push the as outward.
how does the pressure in a star change when going from the surface of the star to the center?
the pressure will increase
in what two ways can a star transport energy outwards?
.
what one factor determines where a star will be found on the main sequence?
the mass of a star
how does the main sequence lifetime depend on the mass and luminosity of a star?
life time = mass / luminosity
What will be the total main sequence life time for the sun?
10 billion years
what will be the life time of a massive O star ?
1 million years
What about a low mass M star?
300 billion years
What is the ZAMS
Zero age main sequence
how is the core of a star changing during the entire main sequence lifetime
drastic changes on the inside cause smaller changes on the outside
in what 3 ways does the surface of a star change during its main sequence lifetime
its gets a little bigger, brighter and cooler
How can we tell the age of a star cluster?
.
when the neuclear reactions in the core end the core begins to the contract. Why?
.
how do you understand what happens to the core in terms of hydro static equilibrium?
.
as the core contracts there are now two energy sources in the center. what are they?
.
how does the energy from the stars center now compare to the energy produced when the star was on the main sequence?
.
what happens to the outer layers of the star?
.
How have the surface temp and luminosity changed as they move into the red giant region?
The temp gets cooler and the luminosity gets brighter.
What is this called and what element results from this reaction?
Helium fusion and it is 3helium to 1carbon plus energy
At what temp does helium fusion start?
1million kelvin
The rate of helium fusion reaction increases very rapidly with increasing temp.how does this lead to an explosion?
Because the electrons are squeezed to tightly
How does the star move on the hr diagram after e star settles down to steady helium burning?
Moves left closer to the main sequence
What happens to the core when it runs out of helium?
It starts burning carbon
Will the sun ever burn elements past helium ?
Yes it will burn carbon
What is a planetary nebula?
A supergiant star that pushes of its outer layers of gas
What heats the gas in a planetary nebula and causes it to glow?
The uv light heats up e gas and causes it to glow
Why can’t the nuclear burning of iron occur?
Because fusion of iron will not give you energy out of the reaction
Once the core is full of iron what happens to the core?
When the core is big enough it will implode
