Astronomy Test 4 Flashcards
The three factors that determine internal pressure
Temperature, rotation, and magnetic fields
The 4 regions of star formation
- Cold regions in interstellar space (H1 regions)
- H2 regions
- Dark nebula
- Bok Globules
Lamda(emission of protons) = 21 cm due to the spin flip of the electrons in the hydrogen atom. what regions on the DR diagram does this occur?
H1 regions
Molecular hydrogen only forms in very cold regions but radiates very little. what regions on the DR diagram does this occur?
H2 regions
Small round nebula. What does this describe?
Bok Globules
A cloud of gas collapses by what?
Mutual gravitational attraction
How do gas clouds become dark nebulas?
Inner regions cool and further collapse after gravitational attraction
What happens after a gas cloud becomes a dark nebula
Internal temperatures and pressures rise and fight collapse
Since cooling can never be efficient enough to reduce the internal pressure enough according to current theories “something” causes further collapse. What is it?
Shockwaves
Where do shockwaves come from? (3 things)
Newly formed stars, supernova explosions, and galactic spiral arms
Further collapse of cloud fragments from dark nebula’s become small, round what?
Bok Globules
Globules further collapse and form what?
Proto-stars
After 1000’s of years a proto-star becomes a star and appears on the ______ on the H-R diagram
Birthline
Dust that surrounds a proto-star and absorbs light
Cocoon nebula
Problems with star formation?
How does a single,isolated star not in a spiral galaxy form? And what if there’s no shocks around?
In the death of low mass stars, Helium fuses to ____ at _______K
Carbon, 100,000,000 Kalvin
In the death of low mass stars, as H is depleted in the core, the core collapses and heats up a H shell around the core and begins to burn and envelope expands. What stage is this?
Red Giant
In the death of low mass stars, the core continues to collapse until T= 100,000,000K. Helium burns explosive because of what?
Quantum degeneracy (all He is at the same temperature)
In the death of low mass stars, outer layers are blown off into interstellar space (planetary nebula) and hot, solid cargo core becomes a ______
White dwarf
In the death of high mass stars, what is the onion skin model. (6 layers)
- H to He
- He to Carbon
- C to Magnesium and Neon
- N to Mg and O
- O to silicon
- S to Fe
In the death of high mass stars, as outer layers crash onto the core, the envelope material is blown off and a _______ results.
Supernova
In the death of high mass stars, if core mass is less than 1.4 then the core remnant is a
White dwarf
In the death of high mass stars, if core mass is greater than 1.4 then the core remnant becomes a
Neutron star
In the death of high mass stars, if core mass exceeds about 3, then the core remnant becomes a
Black hole
No spectroscopic evidence of Hydrogen, light curves rapidly, ejected material has velocities of 10,000 to 20,000 Km/sec. These supernova are the result of nuclear detonations on the surface of a CO white dwarf in a binary system
Type 1 supernova
Spectrum dominated by hydrogen lines, light curves, rise, move slowly, ejects material at speeds of 5,000 mm/sec. Strong radio emitters. These supernovas are the results of a massive single star dying.
Type 2 supernova
Observed in the large Magellenic cloud. Type 2 super nova. Core remnant is probably a neutron star.
Supernova 1978A
First neutron discovers in ____ as a ___
1968; pulsar
Highly magnetized rotating neutron stars, rotate very rapidly, several hundred times per second.
Pulsars
Light emitted by electrons moving in strong magnetic fields.
Synchrotron radiation
When the gravity is so strong that not even nuclear forces can support the star, it collapses to infinity. Thus the star becomes infinitely dense. It becomes a
Black hole
A collection of stars and dust that are gravitationally bound together
Galaxy
The galaxy that we are located in, a spiral galaxy.
Milky Way
The first person to see that the Milky White band that stretches across the night sky is actually made up of myriad of stars
Galileo
During the ____’s who determined we were in the center of the universe after counting stars in 683 regions of the Milky Way
1780’s; William Herschel
Why was Herschel wrong about us being in the center of the Galaxy
He didn’t take into account the gas and dust in the galactic plane that blocks out light from distant stars
Plotted the direction and distances to the star clusters. Studied globular clusters that happens to contain RR Lyrae type variables which can lead us to determine distance to clusters.
Harlow Shapely
Tightly bound clusters of stars
Globular clusters
Variables are pulsating stars which have a period-luminosity relationship, the period of pulsation depends on the absolute magnitude.
RR Lyrae
In the 1930’s ____ discovered interstellar gas and dust
Trumpler
The sun is how many light years away from the center of the Milky Way
25,000 Ly
O and b stars, open clusters, high metal content, type 1 cepheid variables
Stellar population 1
Low mass stars, globular clusters, low metal content, type 2 cepheids
Stellar population 2
The angular change in position due to stellar motions
Proper motion
The speed of a star across the line-of-sight. It is related to the proper motion and depends on the distance of the star.
Tangential velocity
The speed along the line-of-sight measure using the Doppler shift of spectral lines
Radial velocity
The sum of tangential and radial velocities
Space velocity
A point in space that has a velocity equal to the average velocity of all stars including the sun lying within 100 parsecs of the sun. The velocity is around 230 km/sec
Local standard of rest
Once we determine the sun’s distance from the galactic center and the orbital speed, we can calculate the
Orbital period
We can measure the speed of objects around the galactic center at different radii, this is called the
Galactic rotation curves
We live in a spiral galaxy, we’re located in the (not the Milky Way)
Galactic disk between spiral arms
Which types of waves penetrate the gas and dust so that we can study the galactic center.
Gamma-rays and radio waves.
Helium burns causing explosions. This is known as
Helium flash
What determines the life of a star
It’s mass
Do Starr’s move up and down the main sequence?
No
Depends solely on the mass of the star
Gravity
