Exam 1

Question 1

what is the gas between the stars

Answer 1

interstellar medium

Question 2

what happens in molecular clouds?

Answer 2

star formation

Question 3

what is the average size of a molecular cloud

Answer 3

120 light years across

Question 4

what happens in the molecular cloud where some areas are denser than others

Answer 4

self gravity will make these regions collapse

Question 5

collapse and fragmentation of the molecular cloud leads to ….

Answer 5

star forming molecular-cloud cores

Question 6

what happens when a molecular cloud collapses and the center shrinks faster than the outer layers

Answer 6

a protostar is created

Question 7

what is the composition of our milky way

Answer 7

70% Hydrogen, 28% Helium, 2% heavier elements

Question 8

what are protostars?

Answer 8

they are large, cool, and luminous, and they emit infrared light

Question 9

what is the energy source of the protostar?

Answer 9

gravitational energy

Question 10

what happens that makes a protostar into an main sequence star?

Answer 10

the star shrink, and the temp rises in the core and then hydrogen fusion begins making it a main sequence star

Question 11

what is a brown dwarf?

Answer 11

very low mass stars that never start hydrogen fusion

Question 12

what is radiation pressure?

Answer 12

this pressure limits how massive a star can be without blowing itself apart

Question 13

how can material leave the protostar

Answer 13

bipolar outflow of jets

Question 14

what is the nebular hypothesis?

Answer 14

theory about how solar systems form

Question 15

what surrounds the protostar as it is forming?

Answer 15

protoplanetary disk

Question 16

what is the flattened disk around the protostar a result of ?

Answer 16

angular momentum conservation

Question 17

planets and other object form from the..

Answer 17

protoplanetary disk

Question 18

how are planetesmials created?

Answer 18

small particles collide and stick to each other in the disk. small particles are blown into larger ones

Question 19

planetesmails will pull more particles onto them with gravity which will lead to…

Answer 19

planets!

Question 20

asteroid and comets are….

Answer 20

todays remaining planetestimals

Question 21

what is the inner protplanetary disk hotter than the outer regions

Answer 21

because the material that has fallen into the inner disk has fallen farther and has more energy to convert into heat

Question 22

what causes the difference in composition of the protoplanetary disk?

Answer 22

temperature differences

Question 23

what does refractory mean

Answer 23

does not melt at high temps

Question 24

what are substances that can melt or evaporate at moderate temps

Answer 24

volatile

Question 25

what is the name for the track protostars take to becoming a main sequence star

Answer 25

hayashi track

Question 26

how do planets grab gasses from the disk

Answer 26

core accretion-gas capture

Question 27

what does core accretion-gas capture help create for the planet and what is it composed of

Answer 27

the primary atmosphere that is mostly hydrogen and helium

Question 28

how is a secondary atmosphere created on a plantet

Answer 28

by emitting gasses from their interiors ex: volcanos

Question 29

what is the exoplanet detector method that looks for periodic velocity changes in stars

Answer 29

spectroscopic radial velocity method

Question 30

what is mircolensing

Answer 30

it makes a star temporarily brighter, through a planet's gravity focusing it's light

Question 31

what is hydrogen shell burning

Answer 31

H fusion only takes in the shell around the helium core

Question 32

what happens when the He core isn't fusing yet?

Answer 32

gravity wins and the star begins to contract, crushing the HE core

Question 33

what is degeneracy pressure

Answer 33

Laws of quantum of mechanics mechanics prohibits two electrons from occupying the same space

Question 34

how many He atoms does it take to make carbon

Answer 34

three

Question 35

what is the helium flash

Answer 35

core temp rises quickly and starts helium fusion and fusion just skyrockets which causes the core to expand

Question 36

what branch is the star on after the helium flash

Answer 36

horizontal branch

Question 37

what causes the star to enter the asymptotic gaint branch

Answer 37

He is all used up in the core. There is a H and He shells around the carbon core

Question 38

how is a planetary nebula formed

Answer 38

a low mass star is double shell burning and with thermal pulses it ejects the H and He in to space.

Question 39

what is at the center of a planetary nebula

Answer 39

white dwarf

Question 40

true or false: Higher mass white dwarfs are bigger

Answer 40

false

Question 41

In binary star systems what happens to the star that has less mass than its companion

Answer 41

it loses it mass to the larger star and becomes a white dwarf

Question 42

how does a nova happen

Answer 42

material from the more massive binary star companion falls onto the white dwarf until it gets hot enough to fuse H. This cause a small explosion on the stars surface

Question 43

what is the white dwaft limit ( or Chandrasekhar limit)

Answer 43

white dwarfs cant be more massive than 1.4Msun because then electrons would be trying to go faster than the speed of light which is not possibly

Question 44

what is helium capture

Answer 44

high core temps allows He to fuse with heavier elements

Question 45

what is advanced nuclear burning

Answer 45

core temps in stars with greater than 8Msun allow fusion of elements as heavy as iron

Question 46

what is left over after a supernova

Answer 46

a neutron star

Question 47

what kind of super nova is this: iron core of massive star reaches white dwarf limit and collapses into a neutron star, causing explosion

Answer 47

massive star supernova

Question 48

what kind of super nova is this: carbon fusion suddenly begins as white dwarf in close binary system reaches white dwarf limit, causing total explosion

Answer 48

white dwarf supernova

Question 49

how can you tell the difference between types of supernova

Answer 49

light curves and spectra

Question 50

what is a pulsar

Answer 50

the pulses that are coming from a spinning neutron star

Question 51

what wavelengths would be best to use to observe objects in molecular clouds

Answer 51

long wavelengths ( radio)

Question 52

order of how a star forms

Answer 52

1) A cloud contracts under gravity 2) a disk forms 3) nuclear reactions start and star is born 4) clumbs form 5) planetesmials form 6) a wind blows from the central star

Question 53

what can a type 1a supernova help us measure

Answer 53

the distance to a galaxy