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

Week 7 Flashcards by Ellise Boyle

Solar wind and earth

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

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Sun spots

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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Chromosphere

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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Sun percentage of Hydrogen

90%

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Star cluster features

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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Paralax distance

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

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neutrino features

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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How long are stars on the main sequence?

90% (spent fusing H into He)

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Measuring star temp

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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How do atoms form if Nuclei are

positively charged?

High temp causes collisions to occur without repulsion

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aurora

Protons from solar wind interacting with earths atmosphere

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massive stars temp + luminosity

Hotter Temps:more gravitational pressure = higher Temp

- Higher luminosity: Higher T = much higher fusion rates

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Stars with Greater Mass relative lifespan

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

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What makes the sun round?

SPHERICAL nature of gravity and the pressure exerted from the core

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K, M stars

Coolest, red

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Why are some stars not on the Main Sequence?

Not fusing H→He anymore.

- near the ends of their lives.

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How does the sun produce enegry?

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

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

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

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Sun percentage of helium

10%

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High temps enable

more atoms ionized, molecules disassociated.

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A, F, G stars

Middle, yellow

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White Dwarf stars

very dim but hot

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p-p chain fusion

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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Location on main sequence information

gives us mass

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Heliosphere

extension of solar wind

Globular clusters

- 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)

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

No distance must also be considered

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

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

Sun Convection Zone

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

O, B stars

Hottest, blue

Why does the suns heat hence fusion remain relativly constant

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

How do you find star mass?

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

Cooler temps enable

more atoms and molecules can survive

Fusion

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

Granulation

Grainy appearence on photosphere caused by convection currents

What enables sunspots

The Sun rotating differently at different latitudes.

Stellar luminosity

Luminosity = Apparent Brightness x 4pi x distance^2

Solar Wind

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

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

How does temperature affect rate of fusion

higher temp = more fusion

Elements in the Sun

mainly Hydrogen and some helium

Apparent Brightness vs Luminosity

``` 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. ```

Photosphere

Visible surface of the sun where photons leave from

Why doesn't the sun lose mass quickly?

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

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

approx 100,000 years

Giant stars

group of moderately bright but cooler than the sun stars

Size + luminosity realationship

R^2 = L/T^4

Temp required for p-p chain fusion

>5 million K

Supergiants stars

extremely luminous, tend to be <10,000K

Main sequence stars

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

Open clusters

- 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.

Fission

Big nucleus splits into smaller pieces

Evidence of fusion at suns core

Neutrinos observed on Earth

Corona

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

Gravitational Equilibrium

Pressure from FUSION pushing OUT and Gravity from MASS pulling IN

How to determine the age of a cluster

Main-sequence turnoff

Sun Radiative Zone

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

Temp of core of sun

15 million K

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

Outward pressure and gravity

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

lower right

Which is the most common type of Main Sequence star | O,F,G or M?

The spectral sequence sorts stars according to...

Surface temperature

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

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

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

Mass they formed with

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

Core, radiation zone, convection zone, photosphere, corona

Which layer of the sun do we normally see?

Photosphere

How does the Sun generate energy today?

Nuclear fusion