The Sun

Question 1

How many times the diameter of the earth is the sun

and in km

Answer 1

109

1.392m km

Question 2

How massive is the Sun in ME

Answer 2

330,000 Me

Question 3

What type of star is the sun

What population type is it, and what does that mean

Answer 3

G2V

‘yellow dwarf’

It is a population 1 star, which means its heavy element rich

Question 4

How long does the Sun take to orbit the Galaxy

What is its orbit velocity

Answer 4

225-250my

220km/s

Question 5

What is the Sun’s absolute magnitude

What is absolute magnitude

Answer 5

+4.83

The apparent magniture if seen at 10 parsecs (32.6 lys)

Question 6

What is the rotation period of the sun

• at the equator
• at the poles

Answer 6

25. 6 days at the equator (from earth is appears like 28 days)
26. 5 days at the poles

Question 7

In Watts/m², how much solar energy arrives at Earth

Answer 7

1,368 W/m²

Question 8

How extensive (in terms of solar radius) is the Sun’s core

How hot is it?

Answer 8

20-25%

15.7m K

Question 9

What are the sucessive zones out from the core of the sun to the atmosphere

Answer 9

Core –> Radiative Zone –> Tachocline –> Convective zone –> Photosphere –> Atmosphere

Question 10

What is the name of the solar zone, which is the visible surface of the Sun?

Answer 10

Photosphere

Question 11

What is the name for the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto.

Answer 11

Heliosphere

Question 12

What are the three parts of the Sun’s surrounding atmosphere (i.e. not including its visible surface)

Answer 12

The Chromosphere

Transition Region

Corona

Question 13

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

Answer 13

Chromosphere (literallt ‘Sphere of colour’)

Question 14

What doe Corona mean?

Answer 14

Latin ‘crown’

Question 15

What is the name for the period of reduced sunspot activity between 1645 and 1715

Answer 15

Maunder minimum

Question 16

Who discovered the solar cycle of sunspot activity

• what was actually looking for

Answer 16

Samuel Schwabe

between 1826 and 1843

He had actually been looking for the hypothetical planet ‘Vulcan’

Question 17

What is the principal difference between flares and CMEs

Answer 17

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)

Question 18

Aside from SOHO, what is the name of the current main solar observation space mission

What program was it part of

Answer 18

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.

Question 19

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?

Answer 19

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

Question 20

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

Answer 20

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.

Question 21

In what layer is the Sun’s magnetic field generated

Answer 21

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.

Question 22

Under what conditions do convection occur?

Answer 22

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).

Question 23

What creates the Sun’s convective zone

Answer 23

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.

Question 24

What is the fusion mechanism in the centre of the Sun

What are the three components of this

Which component is rare - why?

Answer 24

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

Question 25

What is the dark patch

Answer 25

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.

Question 26

Why is making deuterium so difficult

Answer 26

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.

Question 27

What are the four flare categories and what do they mean

What class do they have to be to affect earth

Answer 27

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

Question 28

When was the most powerful flare recorded
What class was it

Answer 28

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

Question 29

What are the categories of geomagnetic storms

Answer 29

G1 to G5. With the latter being the most extreme with potential grid damage etc