The Sun Flashcards
How many times the diameter of the earth is the sun
and in km
109
1.392m km
How massive is the Sun in ME
330,000 Me
What type of star is the sun
What population type is it, and what does that mean
G2V
‘yellow dwarf’
It is a population 1 star, which means its heavy element rich
How long does the Sun take to orbit the Galaxy
What is its orbit velocity
225-250my
220km/s
What is the Sun’s absolute magnitude
What is absolute magnitude
+4.83
The apparent magniture if seen at 10 parsecs (32.6 lys)
What is the rotation period of the sun
- at the equator
- at the poles
- 6 days at the equator (from earth is appears like 28 days)
- 5 days at the poles
In Watts/m2, how much solar energy arrives at Earth
1,368 W/m2
How extensive (in terms of solar radius) is the Sun’s core
How hot is it?
20-25%
15.7m K
What are the sucessive zones out from the core of the sun to the atmosphere
Core –> Radiative Zone –> Tachocline –> Convective zone –> Photosphere –> Atmosphere
What is the name of the solar zone, which is the visible surface of the Sun?
Photosphere
What is the name for the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto.
Heliosphere
What are the three parts of the Sun’s surrounding atmosphere (i.e. not including its visible surface)
The Chromosphere
Transition Region
Corona
What is the part of the Sun’s atmosphere that is seen to have reddish colour when observed at solar eclipses - and how does this related to its name
Chromosphere (literallt ‘Sphere of colour’)
What doe Corona mean?
Latin ‘crown’
What is the name for the period of reduced sunspot activity between 1645 and 1715
Maunder minimum
Who discovered the solar cycle of sunspot activity
- what was actually looking for
Samuel Schwabe
between 1826 and 1843
He had actually been looking for the hypothetical planet ‘Vulcan’
What is the principal difference between flares and CMEs
Scale
flares are relatively small and local, taking place in the low solar atmosphere, near sunspots where magnetic field lines are concentrated
they are giant bursts of x-rays and energy, they form rapidly and travel out at the speed of light
CMEs on the other hand can be bigger than the sun itself
CMEs form slowly and not produce intense light (essentially a slower lump of gas)
Aside from SOHO, what is the name of the current main solar observation space mission
What program was it part of
the Solar Dynamics Observatory (launched in 2010)
The Living With a Star (LWS) program
The goal of the LWS program is to develop the scientific understanding necessary to effectively address those aspects of the connected Sun–Earth system directly affecting life and society.
The goal of the SDO is to understand the influence of the Sun on the Earth and near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously.
What percentage of the Sun’s radius is taken up by the radiative zone
If the Sun was smaller and cooler, what is radiative zone be bigger or smaller?
And for larger high temperature stars?
about 70%
If the Sun was smaller, the radiative zone would be smaller, and in a very small cool star, might even reach the core.
If it was larger brighter star, the radiative zone would be larger, and for a very high temperatuve star, may even reach the star’s surface
How does energy get transmitted through the radiative zone
How long does it take an individual photon to get through this zone
What is the temperature drop over this zone
The energy generated in the core is carried by light (photons) that bounces from particle to particle
An individual photon takes about a million years to finally reach the interface layer. The temperature falls from 7,000,000° C to about 2,000,000° C over the same distance.
In what layer is the Sun’s magnetic field generated
Sun’s magnetic field is generated by a magnetic dynamo in the tachochline
The changes in fluid flow velocities across the layer (shear flows) can stretch magnetic field lines of force and make them stronger. This change in flow velocity gives this layer its alternative name - the tachocline.
There also appears to be sudden changes in chemical composition across this layer.
Under what conditions do convection occur?
Convection occurs when the temperature gradient (the rate at which the temperature falls with height or radius) gets larger than the adiabatic gradient (the rate at which the temperature would fall if a volume of material were moved higher without adding heat).
Where this occurs a volume of material moved upward will be warmer than its surroundings and will continue to rise further. These convective motions carry heat quite rapidly to the surface.
The fluid expands and cools as it rises. At the visible surface the temperature has dropped to 5,700 K and the density is only 0.0000002 gm/cm³ (about 1/10,000th the density of air at sea level).
What creates the Sun’s convective zone
The convection zone is the outer-most layer of the solar interior. It extends from a depth of about 200,000 km right up to the visible surface. At the base of the convection zone the temperature is about 2,000,000° C. This is “cool” enough for the heavier ions (such as carbon, nitrogen, oxygen, calcium, and iron) to hold onto some of their electrons. This makes the material more opaque so that it is harder for radiation to get through. This traps heat that ultimately makes the fluid unstable and it starts to “boil” or convect.
What is the fusion mechanism in the centre of the Sun
What are the three components of this
Which component is rare - why?
proton-proton (pp) chain
1) protons collide to produce deuterium (rare)
- -> Diprotons are the much more common result of proton–proton reactions within the star, and diprotons almost immediately decay back into two protons.
2) proton collides with deuterium to produce helium 3
3) 2x helium 3s collide to produce helium 4 + 2 protons
What is the dark patch
It is called a Coronal Hole
According to NASA
Coronal holes are variable solar features that can last for weeks to months. They are large, dark areas (representing regions of lower coronal density) when the sun is viewed in EUV or x-ray wavelengths, sometimes as large as a quarter of the sun’s surface.
These holes are rooted in large cells of unipolar magnetic fields on the sun’s surface; their field lines extend far out into the solar system. These open field lines allow a continuous outflow of high-speed solar wind. Coronal holes tend to be most numerous in the years following solar maximum.
Why is making deuterium so difficult
It requires that the incoming proton turn into a neutron at around the time of near collision allowing it to get close enough to the hydrogen nucleus for the nuclear force to take over.
What are the four flare categories and what do they mean
What class do they have to be to affect earth
B, C, M and X
Each one is the 10x more powerful than the last. They are also divided numerically on a scale of 1-9 so you can get a B7 for example
They have to M cor X class to meaningfully affect earth
When was the most powerful flare recorded
What class was it
2003 Halloween time (4 Nov)- so sometimes called the Halloween storms
It was an X43 storm (NASA. ESA estimated X28)
Although that was an estimate because it was too powerful for the measuring equipment which cut out at X17
What are the categories of geomagnetic storms
G1 to G5. With the latter being the most extreme with potential grid damage etc
