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SES 122 > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

what is the gas between the stars

A

interstellar medium

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2
Q

what happens in molecular clouds?

A

star formation

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3
Q

what is the average size of a molecular cloud

A

120 light years across

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4
Q

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

A

self gravity will make these regions collapse

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5
Q

collapse and fragmentation of the molecular cloud leads to ….

A

star forming molecular-cloud cores

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6
Q

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

A

a protostar is created

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7
Q

what is the composition of our milky way

A

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

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8
Q

what are protostars?

A

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

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9
Q

what is the energy source of the protostar?

A

gravitational energy

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10
Q

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

A

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

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11
Q

what is a brown dwarf?

A

very low mass stars that never start hydrogen fusion

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12
Q

what is radiation pressure?

A

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

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13
Q

how can material leave the protostar

A

bipolar outflow of jets

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14
Q

what is the nebular hypothesis?

A

theory about how solar systems form

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15
Q

what surrounds the protostar as it is forming?

A

protoplanetary disk

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16
Q

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

A

angular momentum conservation

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17
Q

planets and other object form from the..

A

protoplanetary disk

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18
Q

how are planetesmials created?

A

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

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19
Q

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

A

planets!

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20
Q

asteroid and comets are….

A

todays remaining planetestimals

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21
Q

what is the inner protplanetary disk hotter than the outer regions

A

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

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22
Q

what causes the difference in composition of the protoplanetary disk?

A

temperature differences

23
Q

what does refractory mean

A

does not melt at high temps

24
Q

what are substances that can melt or evaporate at moderate temps

A

volatile

25
Q

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

A

hayashi track

26
Q

how do planets grab gasses from the disk

A

core accretion-gas capture

27
Q

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

A

the primary atmosphere that is mostly hydrogen and helium

28
Q

how is a secondary atmosphere created on a plantet

A

by emitting gasses from their interiors ex: volcanos

29
Q

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

A

spectroscopic radial velocity method

30
Q

what is mircolensing

A

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

31
Q

what is hydrogen shell burning

A

H fusion only takes in the shell around the helium core

32
Q

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

A

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

33
Q

what is degeneracy pressure

A

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

34
Q

how many He atoms does it take to make carbon

A

three

35
Q

what is the helium flash

A

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

36
Q

what branch is the star on after the helium flash

A

horizontal branch

37
Q

what causes the star to enter the asymptotic gaint branch

A

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

38
Q

how is a planetary nebula formed

A

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

39
Q

what is at the center of a planetary nebula

A

white dwarf

40
Q

true or false: Higher mass white dwarfs are bigger

A

false

41
Q

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

A

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

42
Q

how does a nova happen

A

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

43
Q

what is the white dwaft limit ( or Chandrasekhar limit)

A

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

44
Q

what is helium capture

A

high core temps allows He to fuse with heavier elements

45
Q

what is advanced nuclear burning

A

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

46
Q

what is left over after a supernova

A

a neutron star

47
Q

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

A

massive star supernova

48
Q

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

A

white dwarf supernova

49
Q

how can you tell the difference between types of supernova

A

light curves and spectra

50
Q

what is a pulsar

A

the pulses that are coming from a spinning neutron star

51
Q

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

A

long wavelengths ( radio)

52
Q

order of how a star forms

A

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

53
Q

what can a type 1a supernova help us measure

A

the distance to a galaxy

SES 122 (1 decks)

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