Solar Astronomy

Question 1

Describe telescopic projection

Answer 1

A telescope is pointed at the sun without using an eyepiece. The light from the Sun passes through the telyand the image is projected onto a white card or screen behind the eyepiece holder

Question 2

Describe H-alpha filters

Answer 2

A special filter that only lets through a narrow wavelength(656.3nm) of vision,e light, emitted by hydrogen atoms in the Sun’s atmosphere. They only work through specially designed telescopes

Question 3

Location and relative temperatures of the Sun’s internal divisions

Answer 3

Inwards out:
Core, 15 million Kelvin and where nuclear fusion occurs, energy is gained in the formula e=2.718,c squared
Radiative zone 2-7 million Kelvin, where energy in the form of photons (gamma radiation)
Convective zone 2 million to 5800 kelvin, where energy is transferred to the photosphere by convection currents, the outer ~200,000km of the Sun
Photosphere 5800 Kelvin, the 100km thick visible surface of the sun

Question 4

Location, temperature and density of components of the solar atmosphere

Answer 4

Chromosphere is just above the photosphere, spherical, more dense than corona but still quite low
Roughly 4000k to 25000k it gets hotter with height
Corona is the outer most layer of the Sun, extending millions of km into space. Extremely low density
Around 1-3 million Kelvin, much hotter than the surface

Question 5

Understand nuclear fusion

Answer 5

1. 2 Hydrogen ions (1/1) react to form 1 hydrogen isotope (2/1) as 1 proton decays into a neutron
2. Hydrogen isotope reacts with hydrogen ion to form Helium ion(3/2)
   3 Two helium ions(3/2) react to form another helium(4/2) and two more hydrogen ions(1/1)
   As mass is lost, energy is gained by the formula E = mc squared
   Essentially 6 Hydrogen ions(1/1) go in to form 1 Helium isotope (4/2) and two hydrogen ions (1/1)

Question 6

Structure, origin and evolution of sunspots

Answer 6

The umbra is the dark central region with the strongest magnetic field and the lowest temp. (~3500 k)
The penumbra is the lighter outer region with just higher temperatures and more scattered magnetic fields
Caused by magnetic fields emerging from below the surface and blocking convection, making the area cooler and darker
Often appear in groups, grow and move across the sun as it rotates and fade after days to weeks as the magnetic fields break down

Question 7

How to use sunspots data to determine mean rotation period

Answer 7

Observe the position of the sunspot at a similar time every few days
Rotational period/change in time = 360/change in latitude
If this is repeated for different latitudes, a mean can be found

Question 8

What is the solar cycle

Answer 8

The approximate 11 year period of solar activity measured by counting sunspots over a period of time.
Goes from Solar Minimums - few sunspots to Solar Maximums - many sunspots
Length of cycle = time between solar maximums of minimums

Question 9

How does the sun appear differently when observed from different regions of the electromagnetic spectrum

Answer 9

The shorter the wavelength observed, the more energetic the sun appears

Question 10

Describe the solar wind

Answer 10

“Slow solar wind” - An outflow of charged particles from the Sun’s corona at speeds of ~400km/s
“Fast solar wind” - The same but emitted from coronal holes, and causes stronger gusts of radiation associated with coronal mass ejections and solar flares

Question 11

What are the effects of the solar wind

Answer 11

1. They cause the aurorae when they collide with charged particles in the Earth’s upper atmosphere
2. They cause comet tails to be visible, and point away from the Sun
3. It can trigger geomagnetic storms that cause overloading of power lines and background noise on radio transmissions
4. These storms also can affect electrical components on orbiting satellites or aeroplanes, and pose a risk of radiation to astronauts and passengers

Question 12

Describe the Earth’ magnetosphere, and Van Allen Belts

Answer 12

Concentric circles from North Pole to South Pole, exposed at poles causing aurorae
Van Allen Belts are large, donut shaped rings of charged particles trapped in Earth’s magnetic field. The inner belts have an altitude of 1500 to 10000 km and contain mostly protons. The outer belts have an altitude of 15000 to 50000 km and contain mainly electrons