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PT > Space > Flashcards

Space Flashcards

chap 24+25

1
Q

Gamma rays are produced during fusion in the Sun. How long does it take for the energy to reach the surface due to collisions?

A

100,000 years

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2
Q

What is the temperature in the Sun’s core and surface?

A

core is 1.5x10^6 K (plasma, ionised gas)
surface is 5800 K

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3
Q

At what distance does the Earth orbit the Sun?

A

150 million km

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4
Q

What is the solar mass and how much of it is apart of the total mass of the solar system?

A

2x10^30 kg
99.86%

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5
Q

How large is a light-year? What is it?

A

9.5x10^15 m, distance travelled by light in space in one year

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6
Q

What is our second nearest star and how far?

A

Proxima Centauri, 4.2 light-years

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7
Q

How far is Pluto from the Sun?

A

40x further than what Earth is from the Sun

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8
Q

How far is Proxima Centauri from the Sun?

A

7000x further than what Pluto is from the Sun

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9
Q

How may stars in the Milky way?

A

2x10^11

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10
Q

How many galaxies make up the universe?

A

billions

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11
Q

What is our closest galactic neighbour?

A

Canis Major Dwarf Galaxy

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12
Q

What is our closest spiral galaxy?

A

Andromeda galaxy

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13
Q

If a planet is further..(forces, speed, orbit)

A

experiences less gravitational force, more kinetic energy, smaller speed, larger orbit

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14
Q

If a planet is heavy.. (field)

A

greater field

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15
Q

When are heavy elements produced in a life cycle of a star?

A

when a red supergiant explodes

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16
Q

Countries in the Northern hemisphere

A

rays are more spread out on country, so colder and fewer daylight hours. Those closer to equator do not experience seasons because rays hit them at same angles

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17
Q

When do we see the Moon? How many days to orbit Earth?

A

light from the Sun is reflected from the Moon’s surface, 27.5 days

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18
Q

Define planet and minor planet.

A

a (large spherical) object which orbits the Sun…

planet: without a similar object close to it
minor: but is not large or far enough from other objects to be defined as a planet

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19
Q

Where are most asteroids found?

A

In the asteroid belt between Mars and Jupiter. They are made of left-over pieces of rock.

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20
Q

Define comet. Where does the tail point?

A

a ball of ice, dust and gas which orbits the Sun in a highly elliptical orbit. Away from the Sun

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21
Q

Explain, in terms of energy transfers, why the SPEED of Pluto varies in this way.

A
  • GPE transfers to KE from X to Y or vice versa + from Y to ☓ (so decreases, so increases..)
  • speed decreases as KE decreases
  • most GPE at Y
  • total (of GPE + KE) energy is constant
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22
Q

Why are orbits eplliptical?

How is the object pulled towards the Sun?

A

An object is carried by its momentum from the explosive start of the universe. As it passes the Sun, the force of the Sun pulls it in towards the Sun.

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23
Q

Why are orbits elliptical?

What does the force do?

A

The force causes it to accelerate. The object’s kinetic energy carries slightly further out to the furthest point of the orbit. Slows down and is pulled in again.

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24
Q

The shape of the orbit of the comet from P to Q is circular, with the Sun at its centre.
State and explain the changes in the speed and in the velocity of the comet as it moves.

A

(speed) is constant, as the distance from the Sun is constant

(velocity) is changing as the direction of motion (of the comet) is changing

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25
Q

What to remember for moon phases?

A

One closest to the sun is black, furthest is white.
Bottom becomes less white slowly (black on right).
Top becomes less white (white on right)

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26
Q

State what the phases of the Moon indicate about the motion of the Moon.

A

the Moon orbits the Earth,
the duration of the Moon’s orbit is (approximately) one month 27.5 days

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27
Q

What is redshift?

A

a difference, an increase, in the observed wavelength of electromagnetic radiation from a star or galaxy because it is moving away from us

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28
Q

State one method for estimating the distance d of a distant galaxy from the Earth.

For speed v too.

A

distance: using the brightness of a supernova in the (distant) galaxy

speed: change in wavelength (redshift)

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29
Q

Explain how, according to the Big Bang Theory, (hubble’s constant formula)
represents the age of the Universe.

A

according to the Big Bang Theory, all matter originated from one point and time in space

if the distance a galaxy has travelled is d and the speed it has been moving at is v

the time it has been moving = vd  / (the equation is) AND this is the time from the Big Bang / start of the Universe

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30
Q

Why is this statement incorrect?
The exploding supernova forms a planetary nebula.

A

A, radiation pressure blows the outer shell away to create a planetary nebula (small star). A supernova occurs when a large star explodes, leaving behind a black hole or neutron star.

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31
Q

Graph P and graph Q show how the speed of these distant galaxies changes as their distance from the Earth increases.
In which row are the statements about the Hubble constant and about the age of the Universe
correct?

A

Hubble constant: v/d graph
Universe age: d/v graph

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32
Q

How were the inner, small, rocky planets formed?

A

Planets are formed from materials not pulled into the Sun.

The spinning motion of dust and gas formed an accretion disc.

Gravity pulled the dust and gas together which joined to form rocks, then larger rocks.

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33
Q

Define accretion disc.

A

a rotating disc of matter formed by accretion

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34
Q

Define accretion.

A

the coming together of matter under the influence of gravity to form larger bodies.

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35
Q

Explain how the Sun was formed.

A

Planets could have been formed at the same time as the Sun.

The Solar System began as a huge swirling ball of gas and dust, a nebula. Most of the gas was hydrogen.

The other elements were formed by fusion in other stars which exploded by the end of their lifecycle, sending their contents out into clouds of interstellar gas.

As gravity pulled this mass together, the centre formed a star.

36
Q

How were the gas giants formed? (material gorl)

A

The intense heat forced some of the lighter materials further away and formed the four outer planets.

37
Q

What elements is the Sun made up of?

A

75% hydrogen, 24% helium, 1% others such as oxygen and carbon

38
Q

What energies does the Sun radiate?

A

50% infrared, 40% visible light and 10% ultraviolet (ozone layer absorbs most ultraviolet)

39
Q

What nuclear reaction is the Sun and other stable stars powered by?

A

fusion of hydrogen nuclei into helium nuclei by nuclear fusion

40
Q

What is a stable star? (Remember..)

A

a star that is not collapsing or expanding because the inward force of gravity is balanced by radiation pressure which pushes outwards

41
Q

What is a protostar? (Remember)

A

a very young star still gathering mass from its parent molecular cloud

42
Q

(Just the beginning part)

How is a star formed?

A

Form from clouds of interstellar (occupies space between stars) gas and dust that contain hydrogen called molecular clouds. These are cold and dense enough to collapse and form stars.

43
Q

How far is the Orion Nebula in the Milky Way from us?

A

1350 light-years

44
Q

Explain in detail, the formation of stars.

A

Collapses due to gravitational attraction, starting a series of energy transfers.

Forces of gravity pulls hydrogen gas molecules together. G.P.E is transferred to ke.

As molecules collide, ke is transferred to thermal energy.

The clump contracts into a spinning sphere of super hot gas, a protostar.

Continues to grow by pulling in more material from the molecular cloud. Mass determines its fate.

45
Q

What is radiation pressure?

A

The outward force due to the high temp of the star. Higher core temp= higher pressure. (Makes a star expand)

46
Q

Explain the lifecycle of a star of less than 8 solar masses. (until comparsion)

A

Begins life as a protostar. When it runs out of hydrogen, reactions slow down, there is reduced radiation pressure and the star contracts.

gpe -> thermal. Temp of core and outer shell of helium decreases.

Core becomes hot enough for fusion of helium. There is a bigger electrostatic repulsion between helium nuclei, charge of +2 instead of +1 for hydrogen.

47
Q

How old is the Sun? (more info) (when does it become a red giant and dwarf star?)

A

4.6 billion years old, half-way through its time being a main sequence star (stable star burning hydrogen in it core)

When it expands beyond Earth’s orbit, it will become a red giant. When it becomes a dwarf star, it shrinks to 1% of its size size of Earth

48
Q

Explain the lifecycle of a star of less than 8 solar masses. (after comparsion) All about the outer.

A

Heating the outer shell causes it to expand and cool, turning the star red. It has become a red giant.

Eventually, the core collapses into a white dwarf star. Not hot enough to fuse heavier elements, so it cools to become a black dwarf star.

Radiation pressure blows the outer shell away to create a planetary nebula.

49
Q

Explain the life cycle of a star exceeding 8 solar masses. (until the end of the shells part, red super giant)

A

Also begins as a protostar before entering the stable star period. Core gets so hot, nuclei of heavier elements can fuse. Lighter elements fusion continues in further shells. Outer shell expands to red supergiant.

50
Q

Explain the rest of the life cycle of a star of more than 8 solar masses. (after shells part)

A

Fuel runs out, star collapses and explodes as a supernova. Enough energy to create heavier than iron elements and push them into space as a nebula, along with lighter elements including hydrogen.

Mass of its core determines its fate. Less than 3, neutron star forms. Gravity so strong, protons and electrons forced together. More than 3, black hole, continues collapsing until iit is so dense that light cannot escape.

51
Q

Which stars spend less time as a main sequence star? (bigger muscles and strong..)

A

More massive stars, because higher core temp and use up fuel more quickly

52
Q

What did the Big Bang create?

A

hydrogen, helium, trace of lithium (stars have prod the rest

53
Q

How is the absorption spectrum formed?

A

Dark lines are the wavelengths of light missing from sunlight. Cool gas in the Sun’s atmosphere absorbs them and forms the absorption spectrum.

54
Q

How do astronomers work out the elements in a star?

A

Each element has a unique set of lines, the spectral fingerprint.

55
Q

What happens in Doppler effect?

A

Vehicle moves forward= shorter wavelength= higher pitch

At the back wavelength increases.

56
Q

What is the Big Bang theory? + (what is it doing ever since?) + (What happened before to neutral atoms?)

A

The Universe was created at a single point 13.8 billion years ago and has been expanding and cooling ever since. (was hot and dense, neutral atoms could not forms, instantly ionise)

57
Q

What is Hubble’s Law?

A

how fast distant galaxies are moving away from Earth with a speed, v, that is proportional to their distance, d, from Earth. v=Hod (2.2x10^-18)

58
Q

What is Hubble’s constant?

A

Ratio of the speed at which a galaxy is moving away from Earth to its distance from Earth. (slope of a garph of galaxy speed against distance)

59
Q

What is Hubble’s time?

A

inverse of Hubble constant, which gives the estimate of the Universe’s age

60
Q

State when cosmic microwave background radiation (CMBR) was formed and where we
detect it coming from.

A

It is a wavelength of light in the microwave region . Shortly after the Big Bang, when the universe was formed. Found all points in space.

Expansion of Universe caused wavelength of light to redshift over time.

Two scientists heard noise coming from their telescope, it turned out to be microwave radiation.

61
Q

Why can you not see far into light? When did the universe cool down?

A

Was continuously scattered by charged particles, ions and elecctrons. It’s scattered into fog.
When size of Milky way, cooled down so neutral atoms formed.

62
Q

How can distance to a galaxy be determined using a type 1a supernova.

A

By recording how bright it is and how it appears to be.

63
Q

When do type1a supernova occur?

A

When a white dwarf star in a binary system pulls in material from its companion until it reaches a certain mass and explodes.

64
Q

Explain why it is summer in the northern hemisphere when it is winter in the
southern hemisphere.

A

Ocuurs because of the tilt of Earth’s axis. It is summer in the northern hemisphere as it is tilted towards the Sun. The southern hemisphere is tilted away from the Sun and so it is winter there.

65
Q

Why can nuclear fusion only occur at high temperatures?

A

The nuclei all have the same positive charge so need to be moving fast enough to overcome the electrostatic repulsion.

66
Q

Explain what is a main sequence star.

A

A stable star that is burning hydrogen in its core. Once it has used up 12% of its hydrigen it goes onto another stage of its life cycle.

67
Q

Explain what is a red giant

A

A star that began with fewer than 8 solar masses and is burning helium in its core; its shell of hydrogen has expanded and cooled.

68
Q

Explain what is a white dwarf.

A

The final stage of a star that started with fewer than 8 solar masses after all its fuel has been used up.

69
Q

Explain what is a supernova.

A

An exploding star that began life with more than 8 solar masses and has run out of fuel.

70
Q

Explain what is a neutron star

A

a collapsed star composed almost entirely of neutrons which forms when a star with more than eight solar masses reaches the end of its life

71
Q

Explain what is a black hole.

A

This is the final stage in the life cycle of a star that started with more than 8 solar masses. It has enough mass left over after exploding as a supernova to collapse to a point where gravity is so strong that not even light can escape.

72
Q

Calculate the age of the universe from this graph. (speed in km per s, sitance in million light-years)

A

Find hubble’s constant. Divide by speed of light in km. 1 divided by answer. Convert to years.

73
Q

What do we call a large group of stars?

A

galaxy

74
Q

What causes the redshift in the light arriving from distant galaxies?

A

The galaxies are moving away;
the wavelength is redshifted/increased/ stretched;

75
Q

What two pieces of evidence suggest big bang?

A

Red shift and Cosmic microwave background radiation.

76
Q

Show that 1 light-year = 9.5 × 10^15m.

A

speed formula

77
Q

Explain how this affects the temperature of Pluto as it rotates on its own axis.

A

The white surface is a poor absorber of radiation.

white surface increases in temperature less when facing the Sun

78
Q

The numerical value of H0 is 2.2 × 10–18. State the unit of H0.

A

per second

79
Q

Age of universe.

A

t Universe= d/v = 1/H = 1/2.2x10^-18 = 4.5 ..s = …years

80
Q

Describe how the observed light is different from when it was emitted.

A

wavelength is longer, light has been redshifted towards the red end of the spectrum

81
Q

These measurements suggest that all the Universe was once at a single point.
Explain why.

A

+ more distant galaxies are moving away faster
+ universe is expanding
+ (if galaxies are moving away from each other now, then) in the past galaxies were closer together

82
Q

Describe and explain what happens as an interstellar cloud of gas forms a protostar.

A

Cloud collapses due to gravitational attraction and the internal temperature increases.

83
Q

Describe and explain what happens as a protostar becomes a stable star

A

Gravitational force is inwards. The outward force, radiation pressure, is due to high temperature due to nuclear fusion. The forces are balanced.

84
Q

Describe what happens in the core of a stable star to release energy that is eventually
transferred into space.

A

hydrogen nuclei fuse to become helium nuclei by nuclear fusion

85
Q

Name the galaxy that contains the Sun.

A

Milky Way

86
Q

Explain why this radiation is now in the microwave region of the electromagnetic spectrum.

A

Universe has expanded. Has been redshifted.

PT (15 decks)

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