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Life in the Cosmos > 2-7 > Flashcards

2-7 Flashcards

1
Q

What is the Fermi Paradox?

A

Contradictions between the probability and existence of extraterrestrial life and the evidence for such civilisations

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2
Q

How will we prove the Fermi Paradox?

A

either exploration of the galaxy and beyond or communication with an alien race

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3
Q

When do we have records for life on the plannet?

A

No records for the first 0.5-1 billion years but the following 3 billion years

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4
Q

How old is the earth and our solar system?

A

4.6 billion years old

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5
Q

When was the oldest fossil form of life and what was it?

A

3.6 billion yrs ago - simple cells: prokaryotes

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6
Q

How are the rocks and fossils dated?

A

Radiometric dating

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7
Q

When were the first fossils of animals found?

A

600 million years ago

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8
Q

when did modern humans appear?

A

300,000 years ago

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9
Q

What are the two ways of identifying the ways in which the universe began?

A

Hypothisis driven and discovery science

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10
Q

What is hypothisis driven science?

A

GUess how it happened and then re-create scenario in lab

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11
Q

What is discovery science

A

Seeks examples in nature that might provide vital clues

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12
Q

What is copernicus’ model?

A

The theory that the sun is at the centre and there are other planets, in 1543

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13
Q

What is the scientific method?

A

Ask Questions > Background research > construct hypothosis > Test with experiment > analyse results > true or false&raquo_space; report and if false , reconstruct hypothsis

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14
Q

What happens if a hypothsis is true, after a large number o different testing methods?

A

It achives the status of a law

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15
Q

Why are laws important for science?

A

They provide the underlying basis of scientific speculation, allowing us to pridict things that have not yet been observed

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16
Q

What is cosmic loneliness

A

The growing responsibillity of our responsibillity to planet earth

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17
Q

What is the golden age of astrobiology?

A

new ideas and tech help scienticst from many diciplines answer fundemental questions about life in the universe

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18
Q

What is SETI?

A

Search for extrarerrestrial intelligence

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19
Q

What is a star?

A
  • Ball of plasma held together by its own gravity
  • where nuclear fusion takes place at the core
  • the temprature and luminosity are determined by the stars mass
  • most stars are hydrostatic - at equilibrium between gravitational collapse and outward radiation pressure
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20
Q

What is a temprature luminosity diagram?

A
  • The Hertzsprung-russell diagram shows the temp (X) and luminosity (Y) of stars
  • most stars fall on the main sequence and go from hot and bright (top left) to cool and dim (bottom right)
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21
Q

What is stefan-boltzmann’s law

A
  • hotter stars are the brighter ones
  • luminosity goes up very fast with temprature
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22
Q

What is luminosity

A

Brightness
- Bigger stars have more surface and are brightter

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23
Q

Where do white dwarfs, red giants and red supergiants fall on the HR diagram

A
  • white dwarfs fall bellow the main sequance
  • giants fall above it
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24
Q

What are stars in the main sequence doing?

A

Stars in the main sequence spend most of their time fusing hydrogen into helium

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25
Q

How are the spectral element of stars calculated?

A

Letters O-M, our sun is G

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26
Q

Tell me about our sun

A
  • 150 million km from earth
  • 330,000 times larger in mass
  • G type on the main sequence
  • Surface temp is ~5800K
  • 4.6 billion years old
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27
Q

What is a sunspot?

A

Cooler regions in the solar photosphere due to intense magnetic strength which inhibits convection

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28
Q

What is known as the proton-proton cycle

A

Nuclear fusion - conversion of mass into energy (E=mc^2)

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29
Q

What is the proton-proton cycle

A
  • Two protons fuse to produce deutrium + a positron + a neutrino
  • Another proton fuses with the deuterium to produce a nucleaus of helium and a photon
  • two helium nuclie to produce a single helium with 2 more protons
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30
Q

what is the rate of mass to energy on the sun?

A

~4.2 billion kg of mass is converted to energy a second on the sun

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31
Q

What is the mass of the sun

A

~2x10^30 - so the sun will last 10^10 years (10 billion)

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32
Q

Why is temprature important for fusion?

A
  • for proton-proton cycle, the protons need to come close together
  • normally this would be hard because they have identical charges but with enough speed, they overcome the mutual electrostatic repulsion
  • they need to get less than 10^-15m of each other for fusion - can only be achieved when above 10 million K
  • the heat generated by a star also balances out the inflow of gravitational energy
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33
Q

What is the natural self balancing method?

A

if the star procuces more energy, it expands slightly. the expansion causes it to cool slightly and reduces the energy output and vice versa

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34
Q

How does the mass of a star affect its lifetime

A

Larger stars with more mass have higher temps and faster fusion, so burn up their mass quicker. Smaller ones have lower, so burn for longer

USe the equation ;;;
Lifetime = 1 m (mass)^2.5

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35
Q

Why are only certain stars able to facilitate nursaries of life?

A

Because they are not around for long enough - F - GKM are around for long enough

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36
Q

How many stars in our galaxy are there where there could be life?

A

8 billion stars to study that could have life

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37
Q

what produces the energy of a star

A

PP chain and nuclear fusion

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38
Q

What is a brown dwarf

A

An object with not enough energy to turn on A pp chain

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39
Q

how do we know that stars evolve?

A

by comparing HR diagrams of different star clusters

40
Q

What is the star nutrino problem

A

Models of the sun pridict we need 2-3x more neutrino flux than that which we measure on earth -
The neutrionos emmitted in the pp chain are electron neutrinos, one of 3 types of neutriono. They can change from one type to another, explaining the lower observed flux

41
Q

What are stars created from

A

condensations in the interstellar medium

42
Q

what is the interstellar medium

A

Matter in space, gas (ions, atoms, molecules), dust and cosmic rays

43
Q

what conditons are likley to lead to the formataion of a star in the ISM

A

where ISM is dense and temperatures are low, because the low temp means less internal pressure and more chance of condensation

44
Q

What are some examples of star site formation

A

Dark nebulae - have high concentrations of dust
Elephants trunk 0
Eagle nebula

45
Q

What are the conditions inside a nebula

A
  • High density - upto 10,000-10^6 particles per cubic cm
  • low temperatures - rouughly 10k
46
Q

What is room temprature in kelvin

A

293k

47
Q

How large is a nebula

A

3-10 light years across and contains around ~1000 solar masses of material

48
Q

What is the typical content of a nebula

A

74% hydrogen
25% helium
1% other elements

49
Q

How does star formation take place

A
  1. a dense portion of the nebula begins to collapse under its own gravity (can be triggered by shockwaves) - the material usually has some small rotation which will increase to conserve angualr momentum
  2. The result is a spinning disk of material with a dense core (slows down spinning)
  3. once the density in the core reaches a critical limit, (10 million K) the fusion process switches on and the star is born
50
Q

What is the temprature of a protostar>

A

2000-3000k

51
Q

When and where to planetesmials form

A

at the same time as the formation of the proton star, in the cloud (rotating disk)

52
Q

What happens to stars after they move onto the main sequance?

A

They become hotter and fainter

53
Q

Describe stellar stabillity

A
  • Stars are stable but change does take place
  • sun has become 40% more liminous and 6% larger over last 4.6 billion years
  • the sun will contiunue to increase in size and luminiosity until conditions on earth will be unbrarable for life 1 billion years from now
54
Q

What is the effect of stellar stabillity on our plannet?

A
  • Affect life and evolution
  • galciar activity seems driven by the freqency of sunspots, influencing how much solar raditation reaches earth
55
Q

How long does it take to evolve onto the MS

A

10,000 - 150 m years

56
Q

Describe how elements heavier than helieim are formed

A

By fusion upto iron
exploding stars (supernovae) elements hevaier than iron

57
Q

How much bigger is jupiter than earth

A

11.2x the sizeW

58
Q

What is the order of things in our solar system?

A

Sun, Mercurary, Venus, Earth, Mars, Jupiter, Saturn, Uranus, neptune, Pluto

59
Q

How did the sun form

A
  • disk consisted of 98.5% gas (99% he and H) and 1.5% dust (carbon, iron and silica)
  • formed protostar and planets in 100,000 yrs
  • after 100,000 years, star reaches final mass and switches on as a star - disk turbulance decreases and dust settles into the centre of the disk
  • this is called age zero
60
Q

What factors are relevent for planet formation

A

Turbulence and temprature of and in disk

61
Q

What is important bout terbulance in the formation of planets

A

If too turbulent, particles move too fast and bounce off each other
If less turbulant, greater chance particles collide and stick together

62
Q

why is temprature important for the formation of planets in the disk

A
  • at formation (4.6 billion yrs ago) temp cricial to decide which materials will be used to form which types of plannets
  • temp declines at roughly 1/distnace^2 moving away from the new star
  • critical point is the ice line, beyond which, hydrogen components (like water) condense inot solid ice grains
63
Q

What is the ice line or frost line

A

critical point is the ice line, beyond which, hydrogen components (like water) condense inot solid ice grains

64
Q

What is an astrimonical unit

A

the distance between the earth and the sun

65
Q

Describe the habitation zones around a protostar

A

Inner zone (0.8-1.3 AU) - Dust was very hot and could not contain any residual water (1000K)
2-5 AU - temp remained low, so volitile organic substances can stay solid (below 500K)
beyond 5 AU - water no longer evapourates (less than 150K) - this water ice will be crusial to form the cores of giant plannets

66
Q

What are plants outside of the frezing point made from?

A

Planets outside of the frezing point, at formation, are made mostley of silicates and those mast mars, carbon rich silicates, before those outside of satturen are made from ices

67
Q

How long does it take to form plannets?

A

1000-100,000 years, takes longer than expected because the will be some residual turbulence – if there was no turbulence, objects of a few kilometers in diameter would form in very little time

68
Q

when do planets mature into mid life

A

after around 100,000 years - we expect the central plane to contain around 100 billion objects of 1-10km in size – as they are rotating round the sun, they have many small collisions and gradually accumalate into larger masses

69
Q

How do larger planetesimals form?

A

Inner planets are rocky and stuggle to gapture gas vecuase they have smaller masses
Outer planets have larger masses and a larger gravitational field
After around 1 million years, there will be around 20 objects the size of our moon, which will begin to influence the orbits of other bodies around them

70
Q

What makes the core of the closest planets?

A

Iron

71
Q

What types of planets are produced?

A

Type 1 - Jovians
Type 2 - Terrestrial

72
Q

what are the charicteristics of jovians

A

Jupiter, Uranus, Neptune, Saturn
Hyrdogen and helium
low density
rapid rotation
deep atmouspheres
RINGS
lots of moons
Solid core - rock and ice - can only happen outside the ice line - needs to be > 10x earth mass – the core has the gravitational power to hold the large amounts of gas

73
Q

What are characteristics of terrestrial planets

A

Mercury, Venus, Earth, Mars
High density
rock and metal
slow rotation
solid surfaces
no rings
few or no moons
Have a variety of atmoushphere gasses - co2, nitogen, oxygen

74
Q

What is a comet

A

mostly ice and dust that comes from the outer solar system towards the sun and creates a tail
Left over from creation of solar system -4.6 b yrs ago
Range in size from few miles to 10s of miles
millions of these objects are in the Oort cloud - about 50,000 AUs away to 1 ly away
or in the Kuiper belt - a ring of icy objects beont the orbit of neptune (30-100AU)

75
Q

What is an asteroid

A

small rocky body in the solar system
found mostly in the asteroid belt between mars and jupiter
they range in size gretaly
They used to be thought to be a the remains of a planet that jupiter prevented from forming but there is not enougth material to form a planet
formed 4.6 b yrs ago
different types - almost all contain nickl but classification is based on how much iron is contained
- C - carbonaceous
- S - Silicaceaus
- M - Metatlic

76
Q

What is a meteroride

A

Small particle from an asterioid or comet orbiting the sin

77
Q

what is a meteor

A

an object observed buring up as it enteres the earths atmoushphere (shooting star)

78
Q

what is a meteorite

A

a meteorid that survives its passage throguh earths atmoushere and impacts the surface

79
Q

What was the Hale-Bopp 1977

A

A comet which was obserable for 18 months and the brightest and most observable comet in the 20th c

80
Q

How many astrinomical units make 1 light year

A

63241.1 AU

81
Q

How would comets leave the oort cloud of Kuiper belt?

A

grvaitational pertubation of a nearby star cuases them to change their orbit

  1. enter a hyperbolic orbic, taking them through the solar system once before escaping completky
  2. enter an elliptical orbit and remain trapped
82
Q

What is an elliptical orbit

A

comet that is orbiting a star in an elliptical shape

83
Q

what is a hyperbolic orbit

A

orbit where comet flys through the solar system before escaping completely

84
Q

Describe the tail of a comet

A
  • increases with decreasing distance to the sun
  • pointing away from the sun
  • two tails - ion tail and dust tail (curved)
85
Q

What was comet shoemaker-levy 9 (SL9)

A

greatest collision seen in the solar system
Collision into the side of jupiter in 1994
Fragmented proir to impact
thought to be a mile wide

86
Q

What were the impacts of SL9

A

threw up debris 3000km unot the sky (for one fragement (G))

87
Q

what are the greek camp and the trojans

A

asteroids orbiting with jupiter

88
Q

Tell mne about C type asteroids

A

Carbonaceous Chondrites
C type
75% of all know asteroids
stony and metalic
need a telescope to see

89
Q

Tell me about Silicaceous asteroids

A

S type
17% of asteorids
bright metalic nikel-iron mix with magnesium and iron slicates

90
Q

Tell me about metallic asteroids

A

8% of asteroids
made from iron
bright, mostyly pure iron
only detected by telescopeshe

91
Q

when were most creators produced?

A

around 3.5 billion yrs ago - see on the moon - earth liklkey suffered similar bombardment but weathered away impacts

92
Q

what is ceres

A

largest astroid - diamter of 975 km

93
Q

Why are asteroids not the remains of a destoyed plannet, as once thought?

A

because together, they have the mass of less than 1/1000 of earth so too small

94
Q

What is the Chicxulub crater?

A

180km diamter
66 million years ago
75% of life extinct

95
Q
A

Life in the Cosmos (3 decks)

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