Test 2 Flashcards
Extinction
Loss of star light
Emission Nebula
Excited, glowing hydrogen gas.
Reddish color
Brand new, younger than reflection nebulaes
Reddening
Changing color as it passes through interstellar medium
Dark Nebulae
Dust is thick enough to block light.
Black color
Shedding angular momentum
1) bipolar outflow: material flies out of two poles. Low mass stars.
2) stellar winds: high mass stars.
3) split into 2 stars.
Hyashi tracks
As stars are forming they change positions on the HR diagram making “tracks”
Lifetime of stars equation
t = 1/m^2.5
To form a star
1) Start with a GMC
2) trigger collapse of GMC
- collide GMCs
- supernova explosion
- density waves
3) cloud continues to collapse and spins in a disk
4) once core is hot and dense enough, nuclear fusion occurs
5) stellar winds clear out remaining gas and dust
Russell-Vogt Theorem
The mass and chemical composition of a star determines all it’s other properties.
Most efficient ways to create energy
Low mass star: portion-proton chain
High mass star: CNO cycle
Approximately how long does is take a star like the sun to form?
10,000,000 years
CNO cycle
Method which high mass stars use to convert H to He.
Does a planetary nebula come from high mass or low mass stars?
Low mass stars
Which spectral type of stars is the rarest?
O
What is the term for light changing colour as it passes through the interstellar medium?
Reddening
What process is converting hydrogen to helium in low mass main sequence stars?
Proton-proton chain
What is the maximum mass of a white dwarf?
1.4 solar masses
What’s occurring in the core of a red giant branch star?
Helium core with a shell of hydrogen to helium burning
GMC
Giant molecular cloud: gas clouds in the disk of the Milky Way in which new stars are formed.
Who was the first one to discover pulsars?
Jocelyn Bell
What type of stellar remnant will the sun eventually become?
White dwarf
Which of the following is a method used to shed angular momentum during stellar formation? A. Inward spiral deprecation B. atmospheric oscillations C. Disk fracturing D. Bipolar outflow E. None of the above
D.
Planetary nebula
Outer envelope is ejected into space, exposing the core.
What creates the blue colour seen in a reflection nebula?
Dust reflecting starlight
Which is the shortest amount of time?
A. The lifetime of an M spectral type star.
B. the formation of the sun.
C. The amount of time a high mass star burns silicon into Fe in it’s core.
D. The age of the universe.
E. None of the above.
C.
R and S processes
Rapid and slow neutron capture. Method which creates heavy elements in the universe.
Triple Alpha Process
Helium burning into carbon
Neutron star
Remnant of a type II supernova explosion with mass greater than 1.4 solar masses but less than 3 solar masses.
20 km radius on average.
Asymptotic Giant Branch Star
Double shell burning phase in a low mass star.
Carbon oxygen core is shrinking and not fusing (degenerate core).
He to C shell.
H to He shell.
Envelope expands and cools.
Event horizon
Boundary marking the limits of a black hole. At the event horizon, the escape velocity is equal to the speed of light. Since general relativity states that nothing can travel faster than the speed of light, nothing inside the event horizon can ever cross the boundary and escape beyond it, including light.
Horizontal branch star
Low mass star with a core burning He to C.
Shell of H to He.
Core expands as envelope shrinks.
Supernova type 1
When a white dwarf gets more than 1.4 solar masses rapidly, it will explode.
Helium Flash
Point on HR diagram where He begins fusing into carbon in low mass stars.
Triple alpha process happens.
100,000,000 K
Globular star cluster
100,000 to 1,000,000 stars
Found in halo of galaxy
Old stars
Low metallicity
Photon sphere
Region around black holes where photons orbit.
Pulsar
Spinning neutron star which emits regular pulses.
White dwarf
Remnant of a low mass star. Exposed degenerate core. Carbon oxygen composition. Earth sized. More mass = smaller radius. Can't be more than 1.4 solar masses.
Supernova type II
Last stage in a high mass stars evolution. Once it becomes iron it collapses and the rebounding shock wave blows up the star.
List the three properties that change when comparing a reference frame close to the speed of light with one that is not moving.
1) time
2) mass
3) length in direction if travel
What is the evolutionary stage of a star when it has two shells around a degenerate carbon oxygen core, one shell burning He to C and the other H to He?
Asymptotic Giant Branch
What is the stellar remnant which has between 1.4 and 3 solar masses?
Neutron star
Which spectral type of stars is the most abundant?
O
Which spectral types of stars will live the longest?
O
What causes spaghettification to occur as one falls into a low mass black hole?
Tidal forces in which your feet feel a much greater pull than your head.
Evolution of a low mass star
1) main sequence
2) red giant branch
3) helium flash
4) horizontal branch
5) asymptotic branch
6) planetary nebula
7) white dwarf
What is the term for the balance between gas pressure outward and gravity pulling inward?
Hydrostatic equilibrium
Triggering mechanisms
1) collide GMCs
2) supernova explosion
3) density waves
High mass stellar evolution
1) main sequence: CNO cycle, blue star, very bright, forms fast and does fast.
2) He —-> C core. Shell H —> He
3) C —> O core. Shells: H —> He,
He —> C
4) O —> Ne core. Shells: H —> He
He➡️C, C➡️O. 1 year.
5) Ne➡️Si (silicon) core. Shells: H➡️He, He➡️C, C➡️O, O➡️Ne. 6 months.
6) Si➡️Fe (iron) core. Shells: H➡️He, He➡️C, C➡️O, O➡️Ne, Ne➡️Si. 1 day.
7) iron core collapsesin in about 1/10 second.
Temp reaches 5 billion K.
Gamma rays destroy iron core
Envelope falls in.
Left is a solid core of neutrons and matter bounces off it along with neutrinos.
It’s ejected into space creating a type II supernova.
Black hole
An object where the escape velocity is greater than the speed of light.
Nova
A nova is a cataclysmic nuclear explosion in a white dwarf, which causes a sudden brightening of the star.
Supernova Type I
Faster rate of transfer
Star clusters
Stars are born in groups
Properties:
1) same age
2) same distance
3) same chemical composition
Turn off points
Where main sequence stars leave the main sequence (seen in star clusters).
Roche lobes
The Roche lobe is the region of space around a star in a binary system within which orbiting material is gravitationally bound to that star.
Lagrange points
Specific points where an object will stay indefinitely.
Algol paradox
There’s a red giant star and a main sequence star. The MS star weighs more than the red giant. Since they are binary stars the red giant “gave” it’s mass to the MS star when it evolved. Semi connect binary.
How long is the sunspot cycle?
11 years
Accretion disk
a disklike flow of gas, plasma, dust, or particles around any astronomical object in which the material orbiting in the gravitational field of the object loses energy and angular momentum as it slowly spirals inward.
What is found in the center of a planetary nebula?
White dwarf
Red Giant Branch
Runs out of H.
He in core is not fusing.
Envelope increases and cools. Core shrinks.
H to He shell.
Reflection Nebula
Light reflected off interstellar dust grain.
Bluish color
Ex: Pleiades
Open clusters
100-500 stars
Found in disk of galaxy
Fairly young
High metallicity
Gamma ray busters
The creation of a black hole thru a type II supernova or binary stars colliding, releases a burst of gamma rays.
Photosphere
Sunspots
5800 k
Chromosphere
Prominences
Solar flares
30,000k
Corona
Coronal holes
2,000,000 K
Why do some black hole emit X-rays?
Gas falling into the black hole spirals in and heats up to millions of degrees.
