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Astronomy > Week 7 > Flashcards

Week 7 Flashcards

1
Q

Solar wind and earth

A

Most particles from solar wind are deflected by Earth’s magnetic field. Rest are directed along magnetic field to poles.

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2
Q

Sun spots

A

Cooler Dark spots on sun photosphere, resulting from Magnetic fields trap gas in huge bubbling loops
(Cooler areas at bases of loops are the dark sunspots you see)

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3
Q

Chromosphere

A

Low density layer above photosphere, that is hotter then the photosphere, here hydrogen emits light that gives off a reddish color

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4
Q

Sun percentage of Hydrogen

A

90%

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5
Q

Star cluster features

A
  • Cluster stars are all at the same distance
  • Cluster stars are all about the same age
  • Range of different mass stars!
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6
Q

Paralax distance

A

Distance (parsecs) = 1 / parallax angle (arcsec)

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7
Q

neutrino features

A

Extremely small particles produced from fusion in the suns core, traveling close to the speed of light that (Almost) don’t interact with other matter

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8
Q

How long are stars on the main sequence?

A

90% (spent fusing H into He)

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9
Q

Measuring star temp

A
  1. Peak of thermal spectrum (Wien’s Law)
    -Hotter = bluer, Cooler = redder
    2.Spectral lines
    If there are signs of fragile atoms and molecules, that
    is absorption lines, the temperature must be low
    Red =cooler
    Blue = hotter
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10
Q

How do atoms form if Nuclei are

positively charged?

A

High temp causes collisions to occur without repulsion

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11
Q

aurora

A

Protons from solar wind interacting with earths atmosphere

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12
Q

massive stars temp + luminosity

A
  • Hotter Temps:more gravitational pressure = higher Temp

- Higher luminosity: Higher T = much higher fusion rates

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13
Q

Stars with Greater Mass relative lifespan

A

Shorter Lifetimes as is more lumionous and hence will run out of fuel sooner

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14
Q

What makes the sun round?

A

SPHERICAL nature of gravity and the pressure exerted from the core

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15
Q

K, M stars

A

Coolest, red

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16
Q

Why are some stars not on the Main Sequence?

A
  • Not fusing H→He anymore.

- near the ends of their lives.

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17
Q

How does the sun produce enegry?

A

Fusion, i.e. Small nuclei stick together to make a bigger one creating energy in the process (hydrogen to helium)

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18
Q

Why isn’t gravitational contraction the source of the suns energy?

A

will be more powerful then burning fuel and will take longer to die, but still only approx 20mil years

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19
Q

Sun percentage of helium

A

10%

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20
Q

High temps enable

A

more atoms ionized, molecules disassociated.

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21
Q

A, F, G stars

A

Middle, yellow

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22
Q

White Dwarf stars

A

very dim but hot

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23
Q

p-p chain fusion

A 
In:
- 4 protons (4 x H nuclei)
Out:
- 1 4He nucleus
- 2 photons (gamma rays)
- 2 positrons (anti-electrons)
- 2 neutrinos
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24
Q

Location on main sequence information

A

gives us mass

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25
Q

Heliosphere

A

extension of solar wind

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26
Q

Globular clusters

A
  • Globular Clusters - 100,000 to million stars
  • Tightly bound into a ball. Stars are very dense in core.
  • Tend to be quite old (but not always)
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27
Q

Can stars be compared to each other based on luminosity alone?

A

No distance must also be considered

28
Q

Why isn’t the sun burning fuel to produce energy?

A

burning fuel would require too much mass to be consumed, and would die in approx 2000 years

29
Q

Sun Convection Zone

A

Cooler part of suns radius that carries energy through convection currents (heat rises cooler regions sink) which is faster then radiation

30
Q

O, B stars

A

Hottest, blue

31
Q

Why does the suns heat hence fusion remain relativly constant

A

It has a Solar Thermostat that regulates it
e.g.
Increase temp - increase in fusion - increase in pressure - core expands and cools down

32
Q

How do you find star mass?

A

using Newton’s Version of Kepler’s Third Law. i.e. watch something orbiting the star - only works for binaries. Masses of single stars on main sequence may be inferred from spectral type

33
Q

Cooler temps enable

A

more atoms and molecules can survive

34
Q

Fusion

A

Small nuclei stick together to make a bigger one, occurs in stars

35
Q

Granulation

A

Grainy appearence on photosphere caused by convection currents

36
Q

What enables sunspots

A

The Sun rotating differently at different latitudes.

37
Q

Stellar luminosity

A

Luminosity = Apparent Brightness x 4pi x distance^2

38
Q

Solar Wind

A

Charged particles that escape the suns gravity becasue gas is hot enough to escape through edge of corona

39
Q

How many neutrinos are produced in p-p chain fusion?

A

2

40
Q

How does temperature affect rate of fusion

A

higher temp = more fusion

41
Q

Elements in the Sun

A

mainly Hydrogen and some helium

42
Q

Apparent Brightness vs Luminosity

A 
Apparent Brightness:
-How bright an object appears to telescopes on Earth.
-Depends on distance to observer
Luminosity:
-The actual power output of the object.
-An intrinsic property of the object.
43
Q

Photosphere

A

Visible surface of the sun where photons leave from

44
Q

Why doesn’t the sun lose mass quickly?

A

Energy densities for nuclear reactions are far larger than for chemical.

45
Q

How long does it take for energy to leave the sun?

A

approx 100,000 years

46
Q

Giant stars

A

group of moderately bright but cooler than the sun stars

47
Q

Size + luminosity realationship

A

R^2 = L/T^4

48
Q

Temp required for p-p chain fusion

A

> 5 million K

49
Q

Supergiants stars

A

extremely luminous, tend to be <10,000K

50
Q

Main sequence stars

A

stripe of (dim + cool) to (bright+hot stars)

51
Q

Open clusters

A
  • Open Clusters - 100s to 1000s of stars.
  • Loosely bound together by gravity (if at all).
  • Usually young - older clusters are pulled apart by galactic tides.
52
Q

Fission

A

Big nucleus splits into smaller pieces

53
Q

Evidence of fusion at suns core

A

Neutrinos observed on Earth

54
Q

Corona

A

Extremely low density and high temp layer above chromosphere. Origin of most of the Sun’s X-rays, hard to see except for in an eclipse

55
Q

Gravitational Equilibrium

A

Pressure from FUSION pushing OUT and Gravity from MASS pulling IN

56
Q

How to determine the age of a cluster

A

Main-sequence turnoff

57
Q

Sun Radiative Zone

A

zone in sun interior where energy (gamma rays) from the core is carried outward by photons that are continously absorbed and re emmited

58
Q

Temp of core of sun

A

15 million K

59
Q

What two forces are balanced in what we call gravitational equilibrium?

A

Outward pressure and gravity

60
Q

On the Hertzsprung-Russell diagram, where would you find stars that are cool and dim?

A

lower right

61
Q

Which is the most common type of Main Sequence star

O,F,G or M?

A

M

62
Q

The spectral sequence sorts stars according to…

A

Surface temperature

63
Q

Suppose the distance to a star is doubled. Then the luminosity of the star is…

A

Will remain the same but will and the apparent brightness is decreased by a factor of 4

64
Q

All stars start their lives with the same basic composition. What determines their differences?

A

Mass they formed with

65
Q

What are the regions of the Sun from the centre out?

A

Core, radiation zone, convection zone, photosphere, corona

66
Q

Which layer of the sun do we normally see?

A

Photosphere

67
Q

How does the Sun generate energy today?

A

Nuclear fusion

Astronomy (12 decks)

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